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T. Preda et al.

3.12.6.8 Parathyroid Identication andPreservation ofNormal Parathyroids

Normal parathyroid tissue is London Tan coloured (PANTONE16–1334 TCX Tan) Adenomas are larger, brick red in colour and softer in consistency than thyroid. They have a prominent, polar blood supply with a secondary thyroid capsular supply. They may have adjacent fat and a small normal parathyroid on the surface. Other structures that may confound identication include extra thyroid nodules, brown fat, undescended thymus, intrathyroidal fat, colloid nodules, and reactive and granulomatous lymphadenopathy. Parathyroids may undergo cystic degeneration. Parathyroid carcinomas are similar in colour to parathyroid adenomas but larger, rmer and adherent, with more parasitic blood vessels from the thyroid. Secondary hyperparathyroid glands commonly weigh more than 1000mg and are often subject to repeated haemorrhage, brosis and septated scarring; they may be lighter in colour as a result. Parathyroids have denite planes of separation from the thyroid and other structures. When the parathyroid is embedded in fat or thymus, its mass effect may be interrogated by ballottement with a closed DeBakey forceps showing it moving in undissected fatty tissues or the thyro-thymic tract. When searching unsuccessfully for a parathyroid adenoma, the surgeon is tempted to remove prominent normal parathyroids as an act of desperation. This is a mindset to be eschewed. Patients with mild renal impairment, or pregnancy, typically have upper range normal parathyroids. If a parathyroid adenoma is subsequently discovered, this may lead to hypoparathyroidism.

noma. The routine frozen section enables experience and rapport to develop between pathologists and surgeons. The occasional chastening misidentication of a parathyroid at operation underpins this choice. Thyroid tissue and parathyroid tissue with acinar structures and eosinophilic pseudo colloid can be misidentied by frozen section analysis.

3.12.8 Visual Enhancement

The gamma probe with SESTAMIBI is used by some surgeons to assist in determining the location and completeness of parathyroidectomy and to conrm that a resected specimen is gamma particle avid. In the past, methylene blue IV was used to enhance the appearance of parathyroid glands during operation. More recently, immunouorescent techniques have been reported as well. The cure of 96% of patients with primary hyperparathyroidism with or without the use of these techniques is dependent on surgical experience.

3.12.8.1 Mobilisation andResection

One aims for an R0 resection of the parathyroid adenoma with the gland capsule intact. This avoids the risk of parathyromatosis, which would prevent the cure of hyperparathyroidism. The process involves dissecting the patient from the parathyroid by retracting and dissecting the tissues that surround it. Inadequate exposure can lead to risky dissection of the parathyroid under tension. Care needs to be taken with multifronded, cystic and bilobed parathyroids, which can lead to the retention of functionally active parathyroid tissue.

3.12.7 Use ofFrozen Section

Many experienced parathyroid surgeons do not perform frozen sections routinely but may do so when the identication of a gland is a problem. Less experienced surgeons may remove structures that look like parathyroids and nish the exploration without nding the parathyroid ade-

3.12.8.2 Capsular vs. wider Fat Resection

Most surgeons would perform a capsular dissection of a benign parathyroid adenoma. Careful microscopic examination of the adventitial fat around parathyroids will show small parathyroid rests of parathyroid tissue; these may give rise to persistent or recurrent disease.

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3.12.8.3 Correlation withPreOperative Expectations

Before completion of parathyroid exploration, it is important to review the biochemistry and imaging to make sure that an appropriate parathyroid or parathyroids have been excised, which ts the clinical presentation and, particularly, the expectations from imaging. If this does not add up, then further exploration is required. One example is a high undescended parathyroid antero-inferior to the submandibular gland [9].

3.12.8.4 Rapid PTH Assay

Some surgical units rely on the intraoperative PTH assay to demonstrate biochemical cure. In some cases, this may prompt the need for further exploration. Surgeons can achieve high cure rates with or without the use of these techniques. Sometimes the rapid PTH assay can produce misleading results due to the shortcomings of the technique and its interpretation, including slowfalling PTH in the elderly and those with renal impairment. Intra-operative PTH measurement may be useful in selected cases with unusual anatomical variants. Sometimes internal jugular vein sampling may assist with the lateralisation of the missing adenoma.

3.12.8.5 Weighing theParathyroid

Portable milligram scales have become available and inexpensive online. Either the surgeon or the pathologist should weigh glands trimmed of fat to determine their size compared to a normal parathyroid (30–60mg). Glands weighing more than 300 mg are reassuring, but resection of smaller glands of appropriate appearance may be curative.

3.12.8.6 Parathyroid Marking

When performing sub-total parathyroidectomy and there is potential for re-exploration in the future for recurrent disease, parathyroid gland marking may assist in nding glands and can be achieved with a prolene suture at the non- vascular pole crossed by a medium LIGACLIP®.

3.12.8.7 Non-standard Location Strategy

When the parathyroid thought to be the cause of hyperparathyroidism is not discovered, there are a number of scenarios that need to be considered with a measured and stepwise series of explorations to be carried out.

3.12.8.8 Biopsy ofNormal Parathyroids

The number and location of already discovered normal parathyroids must be considered. Some surgeons perform the biopsy and frozen section to conrm normal parathyroids. This can lead to hypoparathyroidism but if performed carefully is powerful evidence of correct identication by exclusion of the missing parathyroid. The technique is to excise the smallest possible amount of parathyroid tissue (not fat) from the non-vascular pole. This is less than 1mm placed on a suture pack cardboard pledget and immediately immersed into saline solution. An experienced pathologist can cut a small section or imprint the tissue directly onto a slide for the identication of neuroendocrine cells.

3.12.8.9 One Missing Gland

If three normal parathyroids have been seen, then attention is directed to the usual and variant locations of the missing parathyroid (Fig.3.4). Care needs to be taken to ensure that the missing parathyroid is determined to be superior or inferior. The relationship of the other parathyroid to the recurrent laryngeal nerve above and lateral (superior) and below and medial (inferior) will help. The ‘Law of Symmetry’ may assist by deducing the level and anatomical plane from the contralateral gland if seen. If there is no parathyroid seen in the usual locations, then variant locations for the parathyroid should be explored. For missing superior parathyroid, the upper pole should be mobilised to enable a more thorough exploration of the cervical oesophagus, Ligament of Berry and the Cave of Reeve. One unusual location is lateral to the superior thyroid artery at or just

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T. Preda et al.

Fig. 3.4 From the left; anterior and posterior views of typical and most frequent aberrant locations of parathyroid adenomas. Illustrator: Andrea Naga

above the superior extent of the thyroid gland, and occasionally, a parathyroid may be found posterior to the superior thyroid artery proper. Parathyroids may be found deep to the recurrent laryngeal nerve and embedded in clefts at the junction of the tubercle of Zuckerkandl and the upper thyroid pole and beyond the furthest extent of a long tubercle. The retro-oesophageal space is entered on the pre-vertebral plane lateral to the recurrent nerve taking steps to avoid stretching it. This can be explored from the post hyoid level to the superior mediastinum. Rarely one might ‘follow the yellow brick road’ with a vascular fat pedicle leading to the medial aspect of the carotid sheath. The parathyroid may lie on the surface of the common carotid artery or within the sheath in contact with the vagus nerve. The tissue of the lateral part of lymph node level VI along the course of the recurrent laryngeal nerve may contain the parathyroid.

In the case of a missing inferior parathyroid,

the surface of the thyroid from the insertion of the

inferior thyroid artery to the thyro-thymic tract should be explored. The gland may lie within the medial level VI lymph node group or partly embedded in the thyroid inferior pole close to the thyro-thymic tract. Occasionally, this missing gland may lie in the superior mediastinum, deep to the subclavian artery. The thyro-thymic tract on each side should be carefully dened from the lateral and deep aspects of this lymph node group and drawn up by careful dissection and the ‘hand over hand’ technique, clipping inferior thyroid veins as they are encountered. The fascial envelope of the thymus is well developed in younger patients, and the fat lobulation and colour distinguish the thymus from the medial level VI lymph nodes. Care should be taken with both recurrent laryngeal nerves during this mobilisation. The thymus has a characteristic pulsatile indrawing under tension due to its pericardial attachment. When the thymus is delivered, the anterior superior mediastinum is palpated onto the manubrium to search for parathyroids in that location. The

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inferior parathyroids may be intra-thyroid, and this will usually necessitate a hemithyroidectomy. The lobe should be incised with a 22 blade to demonstrate the excised parathyroid.

3.12.8.10 Two Missing Glands

If there are two normal parathyroids on one side, then attention is directed to the other side using the techniques described. Diagonally missing glands need careful determination of whether the missing glands are superior or inferior to determine where to concentrate the search. Two missing inferior glands require careful mobilisation of both thyrothymic tracts paying particular attention to avoiding devascularisation of normal glands. Missing superior glands need the full mobilisation of the superior thyroid poles as detailed above for a single missing superior parathyroid.

3.12.8.11 Three Missing Glands

If only one normal parathyroid has been found, then the exposure and exploration are not adequate; surgical exposure should be improved, and the assistance of an experienced colleague sought. In this scenario even with an adequate exploration, it is occasionally the case that parathyroids are not seen by the surgeon but may be found by the pathologists at cut-up or in histological sections.

3.12.8.12 Malignant Parathyroids andVery Large Parathyroids

If there is biochemical or imaging suspicion of a very large or malignant parathyroid, consideration should be given to resection of the parathyroid and thyroid lobe ‘en bloc’. This might include the level VI lymph nodes as well but the additional benet of this has not been demonstrated.

3.12.8.13 Clearing One Side Strategy

When the parathyroid adenoma that has been excised is of modest proportions, say in the 100– 200 mg range, and there is borderline enlargement of the other parathyroids, a useful strategy

is complete clearance of one side, including the thyro-thymic tract and thymus. This ensures that if a re-exploration is needed, then imaging and surgery should be more limited.

3.12.8.14 Parathyroid Implantation andCryopreservation

If normal parathyroids are inadvertently devascularised or excised, they can be morcellated and suspended in saline for injection graft into the right sternomastoid with the implantation track marked by a medium LIGACLIP®. Cryopreservation is an institutionally based process that requires infrastructure and storage, and cryopreserved parathyroid grafts have a lower success rate than normal parathyroids.

3.12.8.15 Parathyroids beyond theScope ofNeck Exploration

If the steps described have been taken, the success of surgery ranges from 96% to 98%. Multigland, syndromal surgery and re-do surgery all have lower success rates but are still in the range of 85–90%, depending on the institution. It is reasonable to halt exploration once the usual steps in the neck have been carried out. It is important to put the preservation of voice and normal parathyroids at a high priority above surgical ego. ‘Calling a friend’ is a mature and sensible step, bearing in mind there is always in any surgical career, at any stage, someone with more experience who might be involved during the operation or in the aftermath. The most common scenario with a thorough exploration is for an unidentied mediastinal parathyroid. Proceeding to sternotomy without localisation is unwise. Many mediastinal parathyroids may be removed thoracoscopically. In countries with a wider range of individual parathyroid caseloads, missed parathyroids are most commonly in normal positions with misinterpretation of anatomy and limited exposure being the rule rather than the exception. The learning curve for independent parathyroid practice is 100 cases and beyond. There is always much to learn from this remarkably challenging, misleadingly simple disorder.

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T. Preda et al.

3.13 Surgical Outcome Measures

Intra-operative ndings (abnormal parathyroids) can be supplemented by biochemical tests to ensure all hyperfunctioning tissue has been correctly identied and removed. A drop in PTH level to less than 50% of the pre-incision value after the removal of the last specimen is valuable in conrming the absence of remaining hyperfunctioning parathyroid tissue. In secondary hyperparathyroidism, iPTH is slower to fall than in the primary, and iPTH <10 at 30min is ideal with a drop to <2 expected on post-operative day 1.

Longer-term success in parathyroid surgery is dened as normocalcaemia and generally (but not always) normal serum PTH at 6months.

Persistent disease is described as ongoing elevation of serum calcium within 6months of surgery. Recurrent disease refers to normal serum calcium followed by recurrent elevation of calcium after 6 months from surgery has passed. Studies of recurrence rates in parathyroid surgery are limited; however, they do demonstrate that recurrence is often detected between years 5 and 10 with a signicant number occurring after 10 years. Life-long annual monitoring of iPTH and serum calcium is recommended.

3.14 Multi-Disciplinary Care

andEthical Considerations

Optimal care for patients with hyperparathyroidism entails diagnosis, severity assessment, determination of peri-operative risk, localization, resection and subsequent management of calcium homeostasis.

The surgeon should view this larger picture in concert with the family doctor, endocrinologist, renal physician, anaesthetist and other relevant specialists. The patient and their family need evidence- based advice regarding perioperative risks and the expected results of surgery.

The desire and ability to perform surgery with low morbidity and mortality must be weighed against modest benets for older co-

morbid patients with limited life expectancy [10]. Expanded management guidelines may cause ‘mission creep’. The real benets of correcting hyperparathyroidism may be over-stated by a technical enthusiast but equally understated by others.

Surgical caseload impacts the results. Many surgeons do fewer than ve cases per annum. Localisation studies may lead to a false sense of surgical condence. Conversely, limiting surgery to high-volume surgical units diminishes the geographic availability of parathyroid and other surgery. General surgeons can perform parathyroid surgery well at modest volumes when suitably trained. Collaborations between urban and regional surgeons should be encouraged.

Five Takeaways

1. Parathyroid disease is the third most common

endocrine disorder after diabetes and thyroid disease. Primary hyperparathyroidism is the autonomous overproduction of parathyroid hormone (iPTH). Secondary hyperparathyroidism is a physiological response to renal failure and/or low vitamin D, and when autonomy develops, it becomes tertiary hyperparathyroidism.

2. The diagnosis in primary HPT is based on the

history and elevated serum iPTH and calcium. Secondary HPT is diagnosed by marked iPTH elevation responding to low active vitamin D uraemic phosphate retention and hypocalcaemia.

3. Selection of surgical candidates is guided by

the presence and severity of end-organ disease or the risk of these developing together with the assessment of perioperative risk.

4. Pre-operative imaging helps to predict ectopic

or multi-gland hyperplasia and co-existing thyroid disease. It informs the scope of surgery including minimal access or four gland surgery as well as thyroidectomy and thymectomy if necessary.

5. Successful surgical exploration depends on

detailed embryological and anatomical knowledge and systematic patient-gentle bloodless surgery.

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References

1. Zavatta G, Clarke BL. Normocalcemic hyperparathyroidism: a heterogeneous disorder often misdiagnosed? JBMR Plus. 2020;4(8):e10391.

2. Marcocci C, Cetani F, Rubin MR, Silverberg SJ, Pinchera A, Bilezikian JP. Parathyroid carcinoma. J Bone Miner Res. 2008;23(12):1869–80.

3. Bilezikian JP, Brandi ML, Eastell R, Silverberg SJ, Udelsman R, Marcocci C, Potts JT Jr. Guidelines for the management of asymptomatic primary hyperparathyroidism: summary statement from the fourth international workshop. J Clin Endocrinol Metab. 2014;99(10):3561–9. https://doi.org/10.1210/

jc.2014- 1413.

4. Wilhelm SM, Wang TS, Ruan DT, Lee JA, Asa SL, Duh QY, Doherty GM, Herrera MF, Pasieka JL, Perrier ND, Silverberg SJ, Solórzano CC, Sturgeon C, Tublin ME, Udelsman R, Carty SE.The American association of endocrine surgeons guidelines for denitive management of primary hyperparathyroidism. JAMA Surg. 2016;151(10):959–68. https://doi.

org/10.1001/jamasurg.2016.2310.

5. Steinl G, Kuo J. Surgical Management of Secondary Hyperparathyroidism. Kidney Int Rep. 2021;6(2):254–64.

6. Ishani, et al. Clinical outcomes after parathyroidectomy in a nationwide cohort of patients on hemodialysis. Clin J Am Soc Nephrol. 2015;10(1):90–7.

7. Sankaran S, Gamble G, Bolland M, Reid I, Grey A. Skeletal effects of interventions in mild primary hyperparathyroidism: a meta-analysis. JCEM. 2010;95(4):1653–62.

8. Gilmour JR. Grocers’ research scholar the gross anatomy of the parathyroid glands. J Pathol Bacteriol. 1938;46(1):133–49. https://doi.org/10.1002/

path.1700460113.

9. Lee JC, Mazeh H, Serpell J, Delbridge LW, Chen H, Sidhu S. Adenomas of cervical maldescended parathyroid glands: pearls and pitfalls. ANZ J Surg. 2015;85(12):957–61. https://doi.org/10.1111/

ans.12017.

10. Bilimoria KY, Liu Y, Paruch JL, Zhou L, Kmiecik TE, Ko CY, Cohen ME. Development and evaluation of the universal ACS NSQIP surgical risk calculator: a decision aid and informed consent tool for patients and surgeons. J Am Coll Surg. 2013;217(5):833–2.e1-3.

https://doi.org/10.1016/j.jamcollsurg.2013.07.385.

Epub 2013 Sep 18. PMID: 24055383; PMCID: PMC3805776

Parotid

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LaurentFradet andJonathanR.Clark

4.1 Scope ofDisease

The parotid glands are paired major salivary glands encased by the parotidomasseteric fascia. They produce predominantly serous saliva, which is watery and represents about 25% of the daily unstimulated total production of saliva [1]. Saliva has several important functions including lubrication, dental protection, antimicrobial activity, solubilisation of taste molecules, and digestion through amylase [1].

The salivary secretory units are composed of secretory cells arranged in acini and surrounded by myoepithelial cells. Their secretions drain in progressively larger ducts: intercalated, striated, excretory, and collector. The parotid also contains lymph nodes, which are mainly distributed in the supercial lobe. Thus, both benign and malignant neoplasms arising from these tissues, along with inammatory, infectious, and congenital causes, must be considered when investigating a parotid mass (Table4.1).

L. Fradet (*) Division of Otolaryngology, Faculty of Medicine, Université de Sherbrooke, CIUSSS de l’Estrie— CHUS, Sherbrooke, QC, Canada e-mail: Laurent.Fradet@USherbrooke.ca

J. R. Clark Department of Head and Neck Surgery, Sydney Head and Neck Cancer Institute, Chris O’Brien Lifehouse, The University of Sydney, Sydney, NSW, Australia e-mail: Jonathan.Clark@lh.org.au

4.1.1 Benign Salivary Neoplasms

Overall, 75% of parotid neoplasms are benign [1]. Although there are 11 different benign salivary neoplasms described in the most recent edition of the World Health Organisation Classication of Head and Neck Tumours [2], pleomorphic adenomas are by far the most common, representing about 45% of all salivary neoplasia [1]. Also known as “benign mixed tumour”, its name is derived from the fact that it has epithelial, myoepithelial, and chondromyxoid components. Pleomorphic adenomas have a risk of malignant transformation, which typically happens a decade after the initial diagnosis, and are estimated to be around 5–15% [3]. These tumours are thus surgically excised at the time of diagnosis unless the patient has a limited life expectancy or overwhelming comorbidities. The recurrence rate following an appropriate resection is 2.9%, but increases to 26.9% in cases of capsule disruption during the procedure, and up to 80% with gross tumour spillage [3].

The second most common benign salivary neoplasms are Warthin tumours, otherwise known as papillary cystadenoma lymphomato- sum. They comprise 10% of parotid tumours and are typically located in the parotid tail. Approximately 10% of them will be bilateral, and they are strongly associated with smoking. If they are asymptomatic and the clinical, radiological, and cytological features all point towards this

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Table 4.1 Differential diagnosis of a parotid mass

Benign neoplasms Malignant neoplasms Others

Primary epithelial salivary neoplasms

• Pleomorphic adenoma

• Warthin tumor

• Oncocytoma

• Myoepithelioma

• Basal cell adenoma

• Canalicular adenoma

• Cystadenoma

• Ductal papilloma

Other neoplasms

• Hemangioma

• Schwannoma

• Neurobroma

• Lipoma

Primary epithelial salivary tumours

• Mucoepidermoid carcinoma

• Adenoid cystic carcinoma

• Salivary duct carcinoma

• Acinic cell carcinoma

• Epithelial/myoepithelial carcinoma

• Carcinoma ex pleomorphic adenoma

• Polymorphous adenocarcinoma

• Adenocarcinoma not otherwise specied

• Secretory carcinoma

• Lymphoepithelial carcinoma

• Intraductal carcinoma

• Basal cell adenocarcinoma

• Clear cell adenocarcinoma

• Cystadenocarcinoma

• Adenosquamous carcinoma

Other tumours

• Nodal metastasis of a cutaneous primary

• Lymphoma

• Metastasis from another primary cancer (e.g. renal cell carcinoma)

• Sarcoma

• Sialolithiasis

• Acute/chronic parotitis

• Juvenile recurrent parotitis

• Benign lymphoepithelial cyst

• Salivary duct cyst/ retention cyst

• First branchial cleft cyst

• Sialadenosis

• Lymphovascular malformation

• Reactive lymphadenopathy

• Mycobacterial infection

• Cat-scratch disease

• Mumps

• Toxoplasmosis

• Actinomycosis

• Sarcoidosis (uveoparotid fever)

• Granulomatosis with polyangiitis

• Kimura disease

• Rosai-Dorfman disease

• Kikuchi disease

L. Fradet and J. R. Clark

diagnosis, Warthin tumours can be observed with serial ultrasounds. Although malignant transformation has been reported (50 cases worldwide), it is likely that these cases were misdiagnosed [3]. Warthin’s tumours are part of a spectrum of diseases with oncocytosis and oncocytomas that capture technetium in a salivary scintigraphy, due to the high mitochondria content of their oncocytic cells [4].

The other benign tumours, such as myoepitheliomas and basal cell adenomas, are uncommon and do not have specic clinical characteristics. Haemangiomas must be considered in the paediatric population. Facial nerve primary neoplasms, such as schwannomas, and parotid lipomas, are rarely encountered.

4.1.2 Malignant Salivary Neoplasms

Malignant salivary neoplasms are even more diverse than benign neoplasms, with 22 different carcinomas described in the WHO classication

Table 4.2 Primary tumour staging of major salivary gland malignancies, AJCC manual, eighth edition

T stage Description

Tx The primary tumour cannot be assessed T0 No evidence of primary tumour Tis Carcinoma in situ T1 Tumour 2cm or less in greatest dimension,

without extraparenchymal extension

T2 Tumour lager than 2cm but smaller than 4cm

in greatest dimension, without extraparenchymal extension

T3 Tumour larger than 4cm and/or with

extraparenchymal extension

T4a Tumour invading the mandible, ear canal, and/

or facial skin

T4b Tumour invading the skull base, pterygoid

plates, and/or encasing the carotid artery

[2]. The eighth edition of the American Joint Committee on Cancer (AJCC) staging for salivary malignancies is presented in Table4.2.

Malignant salivary neoplasms display a wide range of aggressiveness, based on their degree of differentiation. While low-grade tumours have a

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good prognosis after complete resection and do not typically metastasise, high-grade tumours have a poor prognosis and require more extensive surgery and post-operative radiotherapy. Adjuvant chemotherapy is rarely given for primary salivary cancers, as its benet is unproven [4].

Mucoepidermoid carcinomas are the most common primary salivary gland cancers, accounting for 35% of cases [1]. As the name suggests, they contain mucous, intermediate, and epidermoid cells. They are graded according to their composition (solid versus cystic) and the presence of perineural invasion, necrosis, mitosis, and anaplasia [1]. The MAML2 rearrangement is present in 82% of cases and is highly specic, which is helpful for diagnosis [5].

Adenoid cystic carcinoma is the second most common salivary malignancy. It is an unencapsulated tumour with a strong tendency for perineural invasion, which accounts for the high rate of positive margins and local recurrences (15–85%) [4]. Histologically, it grows in either a tubular, a cribriform, or a solid architecture, the latter having the worst prognosis. Another key feature of this tumour is its strong tendency to produce indolent distant metastases (25–55%), most commonly pulmonary, which may present years after the initial diagnosis [4].

Salivary duct carcinoma is typically regarded as the most aggressive salivary cancer, with rates of distant metastases of up to 75% [1]. Approximately 50% of them arise in the context of a carcinoma ex pleomorphic adenoma, i.e. from a pleomorphic adenoma that undergoes malignant transformation [6]. They typically harbour androgen receptors, and about 40% of cases demonstrate ERBB2 amplication [7]. This has been targeted with Trastuzumab, with promising initial reports, but it has not translated into routine treatment [8]. In the presence of nodal disease, the ve-year disease-free survival is only 19% [9].

Acinic cell carcinomas comprise about 10–15% of salivary epithelial malignancies [1]. They almost exclusively affect the parotid. Although usually slow-growing and low-grade, local recurrence rates are around 35% [6].

Secretory carcinoma, previously known as “mammary analogue secretory carcinoma” (MASC), has similar histopathologic features to the secretory carcinoma of the breast. It is lowgrade and harbours the pathognomonic ETV6- NTRK3 gene fusion [7].

As discussed earlier, there are approximately 20 lymph nodes per parotid, which are mainly distributed in the supercial lobe [1]. These are the rst echelon lymph nodes draining the skin of the upper face and scalp. In countries with high UV exposure and high proportions of Fitzpatrick I–II phototypes, such as Australia, metastatic cutaneous malignancies are the most common type of cancer presenting in the salivary gland [10]. These lymph nodes can also be a site of lymphoma, particularly in patients with Sjogren’s disease.

4.1.3 Infectious, Inammatory,

andMiscellaneous Pathologies

Parotid cysts are not uncommon and may be challenging to distinguish from cystic neoplasms. They typically have no solid component and hence a diagnosis is unlikely to be denitive on cytology. In all parotid tumours, it is essential to match the clinical features with imaging and cytology. Understanding the nuances of these rare and diverse lesions requires considerable experience. If there is any doubt, the patient should be referred to a head and neck specialist surgeon for assessment.

The other most common diagnoses of this category are discussed in the section “non-surgical pathologies and management”.

4.2 Key Elements ofHistory

A thorough history is the rst step in investigating any head and neck pathology. The patient’s age will inuence the most likely diagnosis, with malignancy being more common with advanced age.

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L. Fradet and J. R. Clark

There are no denite associations between smoking or alcohol consumption and parotid cancer, however, tobacco use is associated with Warthin tumours. A history of exposure to ionising radiation increases the likelihood of primary parotid cancer, and UV solar exposure increases the risk of metastatic cutaneous squamous cell carcinoma and melanoma. The surgeon should question the patient on any prior head and neck cutaneous lesion resection, especially from the scalp, forehead, ear, and periocular areas. Patients with a history of immunosuppression, in particular solid organ transplantation, are at very high risk of cutaneous malignancy and parotid metastases compared to the general population. A history of autoimmune disease may be relevant, especially Sjogren’s syndrome. This syndrome may present with a range of parotid disorders such as parotitis, severe sialectasis, benign lymphoepithelial lesions, and non-Hodgkin’s lymphoma. Anticholinergic medications, radioactive iodine therapy, and recent systemic illness predispose to acute parotitis.

The history of the present illness should include a detailed chronology of the mass and associated symptoms such as pain, infection, skin involvement, associated lymphadenopathy, weight loss, and lethargy. The surgeon should specically ask for any history of facial weakness/paralysis or sensory disturbance (pain, paraesthesia, dysesthesia, anaesthesia) in the distribution of the auriculotemporal and great auricular nerves. A relapse-remitting pattern may suggest repetitive inammation of reactive lymphadenitis. Progressive masses are of concern for malignancy.

4.3 Clinical Examination Pearls

A full head and neck examination, including the scalp and facial skin, is warranted for every case of parotid mass. Note should be made of the patient’s skin type and evidence of generalised sun damage, as up to 24% of metastatic cutaneous cancers arise from unknown primary cutaneous sites in patients with widespread actinic changes [11]. Skin examination should focus not

only on current lesions but also on scars that could indicate previous excisions. Examination of the ear canal may rarely demonstrate invasion in cases of malignancy, or that in fact, the primary cancer arises from the ear canal skin with subsequent parotid invasion through the ssures of Santorini or the foramen of Huschke [1]. Examination of the pharynx may demonstrate a fullness of the peritonsillar area in cases of parapharyngeal extension of the tumour. In very rare instances, a deep lobe parotid tumour may invade the post-styloid parapharyngeal cranial nerves. Thus, it is good practice to test the integrity of cranial nerves IX, X, XI, and XII as part of the examination.

Palpation of the parotid will reveal the size of the mass, its approximate location, and its mobility. The rmness and mobility of the mass are important in raising the suspicion of malignancy. Adherence to the overlying skin is a concerning feature and important to note in surgical planning. Palpation of the neck will reveal the presence of clinically involved nodal metastases.

Examination of the facial nerve function is a key element for every case. The function of all ve branches of the nerve should be routinely assessed as demonstrated in Fig.4.1. Any weakness should be documented and is very indicative of an underlying malignant process with facial nerve invasion, which occurs in 12–15% of malignancies at presentation [4]. The House- Brackmann scale has traditionally been used to describe the degree of facial nerve palsy in the surgical literature [12]. It was however designed specically to grade facial nerve recovery following vestibular schwannoma surgery and, thus, is not optimal to describe acute or subacute palsies. The Sunnybrook Facial Grading System describes the resting symmetry, voluntary movement symmetry, and synkinesis of different regions of the face, and is the most commonly used scale in the rehabilitation literature [13]. Similarly, the eFACE scoring system, an electronic assessment scale described in 2015, also evaluates static, dynamic, and synkinetic parameters for each region of the face [14]. It can be used as a mobile phone electronic application and has a moderately strong agreement with the Sunnybrook scale [14].

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