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SRB's Manual of Surgery
Fig. 6.4: Ectopic sites of thyroid.
Ectopic thyroid tissue may lie anywhere along the line of
descent. Whole of the thyroid gland or residual thyroid lies in an
abnormal position either in the posterior part of the tongue, or
in the upper part of the neck in midline, or intrathoracic region.
Carcinoma develops more commonly in ectopic thyroid tissue
than normal thyroid. Radioiso tope scan, CT scan for intrathoracic
thyroid will confirm the diagnosis.
Lingual Thyroid
It is the thyroid tissue in the midline posterior third of the tongue
at the foramen caecum (i.e. anywhere between circumvallate
papillae and epiglottis), presenting as rounded swelling (pink
rounded strawberry like mass). There is embryonic failure of
normal thyroid tissue to descend from the foramen caecum area
of the tongue base through the lower neck.
It may be the only existing thyroid tissue which may cause:
¾
Dysphagia, pain, speech impairment, stomatolalia
(speech with clogged nostrils), foreign body sensation,
cough, snoring, sleep apnoea.
¾
Respiratory obstruction, haemorrhage.
¾
70% present as hypothyroidism, 10% as cretin.
¾
Common in females (3:1).
¾
Symptoms coincide with puberty, pregnancy.
Bare tracheal rings in midline with absence of normal thyroid
tissue may often be evident (66%).
Incidence is 1:100,000. 90% of all ectopic thyroids are found
to be lingual thyroids.
Any diseases which can occur in normal thyroid can also
occur in lingual thyroid, i.e. nodularity, toxicity, malignancy
(If turns malignant, follicular carcinoma is more common,
papillary carcinoma is very rare).
DIFFERENTIAL DIAGNOSIS FOR LINGUAL THYROID
B
x Carcinoma of posterior third of tongue
x Angiofibroma, haemangioma, lipoma, papilloma
x Sarcoma, minor salivary gland tumour
x Hypertrophied lingual tonsil
A
B
Figs. 6.5A and B: Lingual thyroid visible on the posterior 1/3rd of
the tongue.
normal thyroid.
A
Neck should be palpated for the presence or absence of
Investigations
Radioisotope study shows the uptake of iodine by the lingual
thyroid and also shows the status of the thyroid in normal
B
Figs. 6.6A and B: Technetium-99 radioisotope scan in lingual thyroid.
USG of neck is done to assess lingual thyroid and normal thyroid region.
fossa. Technetium
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99m
pertechnetate IV injection and dynamic
and static lms in 20 minutes also delineates the ectopic and
normal gland better.
Ultrasound neck has to be done to see the absence of thyroid
in normal location.
MRI is very useful in lingual thyroid.
Endoscopy guided FNAC/tissue biopsy is done to confirm
or if lingual thyroid is suspected to be pathological, but is
controversial.
Thyroid function tests should be done. Commonly, it is
hypothyroid but rarely can be toxic.
Treatment
L-thyroxine is given daily orally.
Surgical excision is indicated in a large lingual thyroid with
obstructive features, bleeding, ulceration, cystic degenera-
tion or malignant transformation. Usually it is done through
transoral approach. Energy sources like harmonic device or
laser is very useful in avoiding troublesome bleeding and
safe extirpation. Mucosa is sutured after excision using
polyglatin. Occasionally mandibulotomy and tongue splitting/
transhyoid/suprahyoid or lateral pharyngotomy incision as
external approach may be needed when there is malignancy
or very large mass.
Radioisotope therapy for ablation is also often used.
447
CHAPTER 6 Thyroid
A
Figs. 6.7A and B: Thyroglossal cyst.
B
Thyroglossal Cyst
Thyroglossal cyst is a swelling occurring in the neck in any
part along the line of thyroglossal tract.
It is due to failure of the thyroglossal duct/tract to obliterate
completely; there will be persistent duct at certain part
forming cystic swelling containing mucus fluid.
POSSIBLE SITES FOR THYROGLOSSAL CYST
B
a. Beneath the foramen caecum
b.
In the floor of mouth
Suprahyoid
c.
d.
Subhyoid—commonest site 65%
On the thyroid cartilage—2nd common site
e.
It is usually congenital wherein there will be degene ra tion of a
part of the tract causing cystic swelling. Normal thyroid may
be present in the normal location (fossa). Sometimes, thyroid
may not be present in the normal site but may be present in
the wall of the thyroglossal cyst.
It is a tubulodermoid type of cyst.
It is lined by pseudostratified, ciliated columnar epithelium.
Features
Swelling in the midline, towards the left.
Moves with deglutition as well as with the protrusion of
tongue. Patient is asked to open the mouth and keep the
Fig. 6.8: Thyroglossal cyst in a boy. It is a mid
‘TUG’ feeling while protruding the tongue out.
Fig. 6.9: Infected thyroglossal cyst.
line swelling with a
lower jaw still. Examiner holds the cyst between the thumb
and forefinger. When the patient is asked to protrude the
tongue, a “tugging sensation” can be felt.
Swelling is smooth, soft, fluctuant (cystic), non tender,
mobile, often transilluminant.
Thyroid fossa is empty, if there is no thyroid in normal loca-
tion.
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Thyroglossal cyst can get infected and may form an abscess.
Cyst wall contains lymphatic tissue and so infection is
common.
Malignancy can develop in thyroglossal cyst (papillary
carcinoma)—1%. Cyst will be harder, fixed, with palpable
neck nodes. More often it is difficult to suspect and will be
confirmed by histology after excision. If biopsy report is
papillary carcinoma, then completion thyroidectomy is indi-
cated if the remaining part is nodular thyroid or shows cold
nodule or there are enlarged neck nodes, or with history of
neck irradiation. If neck nodes are present, node dissection,
and radioactive iodine therapy with suppressive dose of L
SRB's Manual of Surgery
thyroxine 0.3 mg OD is needed.
Incidence is equal in both sexes.
Investigations
a. Radioisotope study—Technetium
b. Ultrasound neck; T3, T4, TSH estimation.
c. FNAC from the cyst.
DIFFERENTIAL DIAGNOSIS FOR THYROGLOSSAL CYST
B
x Subhyoid bursa
x Pretracheal lymph node
x Dermoid cyst
x Solitary nodule of thyroid—
isthmus
99m
pertechnetate scan.
x Submental lymph node
x collar stud abscess
b. If there is no normal thyroid gland after the surgery, mainte-
nance dose of L-thyroxine 0.1 mg OD is given life long.
Note:
• If tract is not completely excised, it will result in thyroglossal fistula.
• Koempel’s suprahyoid technique is more aggressive approach occasion-
ally used in recurrent disease.
Thyroglossal Fistula
It is not a congenital condition. It is acquired.
It either follows infection of thyroglossal cyst which bursts
open or after inadequate removal of the cyst.
It is lined by columnar epithelium, discharges mucous and
is a seat of recurrent inflammation. “Hood sign” is characteristic. Opening of fistula is indrawn and been overlaid by a
fold of skin as ‘hood’.
Peculiar crescentic appearance is called as semilunar sign.
It secretes mucus discharge.
Site of the fistula is just below the hyoid bone commonly; in
infants it may be much lower.
Investigations: Radioisotope study and fistulogram.
Treatment: Sistrunk operation.
Note:
One more sistrunk operation is done in case of lymphoedema.
Treatment
a. Sistrunk operation:
Excision of cyst and also full tract upto the foramen caecum
is done along with removal of central part of the hyoid bone,
as the tract passes through it.
Technique
Through transverse neck incision placed over the cyst, skin
flap is raised above along with platysma. Care should be
taken not to open the cyst. Cyst with surrounding tissues
is dissected up to the hyoid bone. Sternohyoid and thyro-
hyoid muscles are divided. Central part of the hyoid bone
of 1 cm width is resected along with intact track within it.
Geniohyoid and mylohyoid muscles are divided off from
the hyoid. Track with adjacent tissues is dissected above
upto the foramen caecum. Adjacent tissues also should be
removed because of possibility of multiple tracks which
otherwise lead to recurrence or fistula formation. Often
anaesthetist is asked to apply digital pressure over the base
of tongue near foramen caecum to facilitate the dissection
and to confirm the reach up to the foramen caecum. Track
is ligated at foramen caecum and removed. Recurrence
rate by removal of only track without central hyoid is 25%.
Removal of track with central hyoid of 1 cm width reduces
the recurrence rate to 5%. Complications are recurrence,
thyroglossal fistula formation, haemorrhage/haematoma
formation and infection. Low lying cyst often requires two
parallel incisions to remove entire track up to foramen
caecum.
Fig. 6.10: Thyroglossal fistula.
Lateral Aberrant Thyroid
By definition, Lateral aberrant thyroid is a mass of tissue
having the structure of a normal or pathological thyroid
gland, but situated at some definite distance from the normal
thyroid, with which it has no connection, or more strictly,
lateral to the jugular vein.
Condition is presently considered as misnomer. Mostly, it
is due to metastatic deposit from thyroid carcinoma, mainly
papillary carcinoma of thyroid.
FNAC confirms the diagnosis and is treated like metastatic
papillary carcinoma thyroid (Differentiated thyroid cancer).
Agenesis
Total agenesis of one thyroid lobe may occur. This is rare but
can be clinically important. It leads to confusion in diagnosis,
especially in the toxic gland, where it could be diagnosed as
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a secreting nodule.
Dyshormonogenesis
It is an autosomal recessive condition wherein there is either
deficiency of thyroid enzymes (either peroxidase or dehaloge-
nase) or inability to concentrate or to bind or to retain iodine.
There is an inherited defect in hormone biosynthesis.
It may be familial and patient presents with large diffuse
vascular goitre involving both lobes.
They respond very well to L-thyroxine and may not require
surgery
Note:
Pendred’s syndrome: It is congenital hypothyroidism associated with
congenital sensorineural deafness. CT scan of temporal bone shows
abnormal bony labyrinth. Condition shows thyroid peroxidase deficiency.
THYROID FUNCTION TESTS
1. T3 (Serum tri-iodothyronine): 1.2–3.1 nmol/litre (60–180
ng/dL). 80% of T3 is from deiodination of T4 at periphery
in liver, muscle, kidney and pituitary. T3 is 4 times more
potent with half life of 24 hours.
2. T4 (Serum thyroxine): 55–150 nmol/litre (4–11 mg/dL). It
reflects the output of the gland (Edward Calvin Kendall 1915).
3. TSH 0–5 IU/ml of plasma. TSH is secreted from anterior
pituitary; its secretion is inversely related to circulating
thyroid hormones. TSH secretion is regulated by TRH from
hypothalamus.
4. PBI (Protein-bound iodide)—8 mg/100 ml.
5. Free T3 is 0.3% (3-9 nmol/litre). It is the best single test in
assessing hyperthyroidism.
6. Free T4 is 0.03% (8–26 nmol/L).
7. RA I
8. TRH stimulation test for hypothalamic—pituitary axis:
9. Serum creatinine is increased in hyperthyroi dism; decreased
10. Serum cholesterol is increased in hypothyroi dism and
11. BMR is increased in hyperthyroidism.
12. Thyroid autoantibodies are also useful to evaluate the
123
scan can show either cold nodule, hot nodule, or
warm nodule.
Intravenous TRH (200 µg) shows rise in serum TSH level
in 20 minutes (from basal 1 µ unit/ml to 10 µ unit/mL)
and reaches to normal in 2 hours. Patients with pituitary
insufficiency develop a subnormal response; patient with
hypothyroidism will show enhanced TSH response; in
hyperthyroidism there will be no response. This test is
useful in doubtful hyperthyroidism, hypothyroidism, T
thyrotoxicosis, ophthalmic Graves’ disease.
in hypothyroidism.
decreased in hyperthyroidism.
function (LATS). TSH receptor antibodies (TSH RAb) has
got long-acting potential and are reasons for all primary
thyrotoxicosis.
13. Werner’s T3 suppression test: Initial isotope uptake study
is done. 40 µg of T3 is given to the patient orally 8th hourly
for 5 days. Uptake study is repeated. In normal uptake
suppression up to 80% is noted. In toxic goitre suppression is 10–20%. It is used in patients with antithyroid
drugs for primary thyrotoxicosis to assess the remission
status.
14. Thyroglobulin estimation: Normal value is 0.5–50 µg/L. It is
used during follow-up period especially in follicular carcinoma of thyroid. But if thyroglobulin antibodies are raised
in patient, then it is of no use. Thyroglobulin is produced
only by the thyroid tissue. After total thyroidectomy, its
level drastically reduces. It is the ideal follow-up marker in
well-differentiated thyroid carcinoma after thyroidectomy.
Sudden raise in its serum level can occur in thyroiditis,
primary or secondary toxic goiter.
FNAC OF THYROID
It is the investigation of choice in most of the thyroid diseases
to conclude pathological diagnosis.
It is useful in papillary/medullary (amyloid)/anaplastic carci-
nomas, lymphomas, colloid nodule, thyroiditis.
23G needle is used. Suspicious solitary/multiple nodules/
dominant nodules should be aspirated.
Karolinska hospital (Lowhagen) at Sweden pioneered this
method.
Minimum six aspirations should be done. An adequate FNAC
smear should have six aspirations with six groups of cells
with each group containing 20 cells. USG-guided aspiration
is better.
Diagnostic accuracy of FNAC is 95%; sensitivity 85%; speci-
ficity 94%.
Aspiration is graded as: Thy 1—Nondiagnostic; Thy 2—
Nonneoplastic; Thy 3—Follicular; Thy 4—Suspicious of
malignancy; Thy 5—malignancy.
In a cyst of thyroid FNAC may be less reliable; if cyst recurs
after 3 aspirations, surgery is needed.
Malignancy rate in a simple cyst is 5%; in a complex cyst,
it is 75%.
FNAC is not reliable at present in follicular carcinoma of
3
thyroid as capsular and vascular invasions cannot be found.
But by newer technique it is possible to identify the differences—Benign is polyploidy, malignant is aneuploidy; benign
are monoclonal, malignant are polyclonal; MR spectroscopy
and thyroimmunoperoxidase estimation are useful to differentiate.
FNNAC (fine needle nonaspiration cytology)—is said to be
more reliable.
449
CHAPTER 6 Thyroid
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USG IN THYROID
B
x To identify nodules, number, size, vascularity, echogenicity
x To do USG-guided FNAC
x To identify neck lymph nodes
x To find out solid or cystic nature
x Benign lesion is hyperechoic, often cystic with well-defined
margin; shows peripheral egg shell calcification with sonolucent
rim (halo) around nodule
x Malignant lesion is hypoechoic with poorly defined margin, with
high vascularity, with microcalcification without any halo around
SRB's Manual of Surgery
CLASSIFICATION OF GOITRE
Goitre is enlargement of thyroid gland. (‘goiter’-Latin-guttur-throat)
1. Simple nontoxic
a. Diffuse hyperplastic:
–
Physiological
-
Puberty.
-
Pregnancy.
–
Primary iodine deficiency (Endemic; dietary iodine
intake less than 100 µg/day).
–
Secondary iodine deficiency:
-
Goitrogens of Brassica family, e.g. cab bage, soya
bean. Common in hill stations.
-
Excess dietary fluoride.
-
Drugs: PAS, lithium, phenylbutazone, thiocyanates,
potassium perchlorate, antithyroid drugs, radioactive iodine.
-
Dyshormonogenetic goitre.
b. Colloid goitre.
c. Nodular goitre (Multinodular).
d. Solitary nontoxic nodule.
e. Recurrent nontoxic nodule.
f. Wolff-Chaikoff effect (1948): Intake of large quantity of
iodides inhibits the further release of thyroid hormones
(inhibits organification) by autoregulatory mechanism; but
later may cause escape phenomenon.
g. Hokkaido goiter: Hokkaido is northern island in Japan
where iodine rich seaweeds are the main diet intake of
which causes goitre in these individuals. Patients are
euthyroid.
2.
Toxic
a. Diffuse (Primary)—Graves’ disease.
b. Multinodular (Secondary)—Plummer’s disease.
c. Toxic nodule (solitary) (Tertiary).
d. Recurrent toxicosis.
3. Neoplastic
a. Benign—adenomas: follicular, Hurthle cell.
b. Malignant:
–
Carcinomas: Papillary, follicular, medullary, anaplastic.
–
Lymphomas.
4. Thyroiditis
a. Hashimoto’s autoimmune thyroiditis.
b. de-Quervain’s autoimmune thyroiditis.
c. Riedel’s thyroiditis.
5. Rare causes: Bacterial (suppurative), amyloid.
A B
Figs. 6.11A and B: Note the goitres in (A) male and
(B) female patient.
A
Figs. 6.12A and B: Familial goitre. Goitres in brother and sister.
A B
Figs. 6.13A and B: Familial goitre running in sisters.
WHO GRADING OF GOITRE
B
Grade 0: No visible or no palpable goitre.
Grade 1:
Grade 2:
A B
Palpable thyroid/goitre but not visible in normal positioned
neck.
goitre which is visible in normal positioned neck.
Figs. 6.14A and B: Large goitre in two female patients.
B
IN A CASE OF THYROID DISEASE, FOLLOWING THINGS
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B
SHOULD BE MADE VERY CLEAR
x Functional status—hyperthyroid/euthyroid/ hypothyroid
x Compression on trachea/recurrent nerve
x Neck lymph nodal status
x Tracheal deviation
x Carotid infiltration
x Retrosternal extension
x Systemic features like toxicity or malignant spread to different
organs like bone/liver/lungs
DIFFUSE HYPERPLASTIC GOITRE
Initial persistent increase in TSH level causes diffuse active
lobules. In late stages of diffuse hyperplasia,TSH stimulation
decreases and many follicles become inactive, get filled with
colloid and it is called as colloid goitre. As diffuse hyperplastic
goitre is a reversible stage, L-thyroxine is beneficial.
↓
Nodule formation.
↓
Centre of the nodule is inactive and only margin is active, i.e.
internodular tissue is active.
↓
Formation of many nodules.
↓
Multinodular goitre (MNG).
Other factors involved are growth-stimulating immunoglobu-
lins and growth prone cell clones.
STAGES OF MULTINODULAR GOITRE FORMATION
B
x Stage of hyperplasia and hypertrophy
x Stage of fluctuation in TSH
x Stage of formation of nodules (inactive); (inter-nodular tissues
are active)
Colloid goitre is a goitre due to long-standing iodine deficiency with
localised accumulation of significant colloid in the gland.
451
CHAPTER 6 Thyroid
Fig. 6.15: Diffuse hyperplastic goiter.
MULTINODULAR GOITRE (MNG)
MNG is discordant growth with functionally and structurally
altered thyroid follicles presenting as multiple nodules in thyroid.
It may be due to mainly fluctuation in TSH level; other
causes may be iodine deficiency, goitrogens, hereditary,
dyshormonogenesis.
Pathogenesis
Persistent TSH stimulation.
↓
Diffuse hyperplasia of gland (all active lobules).
↓
Later with fluctuation of TSH level.
↓
Mixed areas of active and inactive lobules develop. It is also
probably due to increased sensitivity of follicular cells to TSH.
↓
Active lobules become more vascular and hyperplastic.
↓
Haemorrhages occur with necrosis in the centre.
Fig. 6.16: Examination of the thyroid gland from behind for any
nodules. Thyroid enlargement in male is rare.
be malignant.
Fig. 6.17: Multinodular goitre.
Nodule in a male could
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Clinical Features
More common in middle aged females (10:1).
It is a slowly progressive disease with many years of history.
Multiple nodules of different sizes are formed in both lobes,
also in isthmus, which is firm, nodular, nontender, moves
with deglutition.
Recent increase in size signifies malignant transfor mation
or haemorrhage.
Positive Kocher’s test is due to compression over trachea
(tracheomalacia/scabbard trachea) in a long-standing MNG.
Nodule when calcified becomes harder; necrosis softens
SRB's Manual of Surgery
Fig. 6.18: Pizzillos method to make the thyroid more
prominent while examining.
the nodule.
COMPLICATIONS OF MNG
B
x Secondary thyrotoxicosis (30%)
x Follicular carcinoma of thyroid (10%)
x Haemorrhage in a nodule
x Tracheal obstruction, calcification
x Cosmetic problem
Note:
Thyropharyngeus and cricopharyngeus parts of inferior constrictor muscle
are attached to thyroid and cricoid cartilages respectively; during swallowing
these muscles will contract to move thyroid and cricoid cartilages upwards.
Thyroid is attached to larynx (cricoid) through condensed pretracheal fascia,
Berry’s ligament. So thyroid moves upwards with deglutition.
Fig. 6.19: Recurrent nodule thyroid. Note scar of previous surgery.
Fig. 6.20: Thyroid swelling moves on deglutition because of attachment
of pretracheal fascia through Berry’s ligament to cricoid cartilage and
to constrictor muscles.
Fig. 6.21: Multinodular goitre. Note the nodules marked.
Fig. 6.22: Large multinodular goitre.
Investigations
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T
, T4, TSH, free T4, US neck, FNAC. FNAC is done from
3
most dominant and suspicious nodule. FNAC from more than
one nodule is better; US-guided FNAC is more reliable. High
resolution US identifies impalpable nodules, number, nature
of nodule, vascularity of nodule. Nodule less than 0.3 cm is
identifiable in US.
X-ray neck shows ring or rim calcification; also reveals the
position (displacement) and compression of trachea.
Indirect laryngoscopy to see vocal cords prior to surgery
(This is mainly for documentation and legal purpose as even
in individual with normal voice, one of the vocal cords may
have been paralyzed by viral infection like mumps, probably
during childhood and have compensated)—occult recurrent
laryngeal nerve (RLN) palsy).
Radioisotope iodine scan—in selected patients when indi-
cated only.
Routine blood investigations, serum calcium.
CT scan/MRI are routinely not indicated. It is done in retros-
ternal extension.
Treatment
Usually surgery is preferred. Reason for doing surgery in nodular
goitre is—it is an irreversible stage and chances of complications like development of toxicity, haemorrhage and follicular
carcinoma are high and also for cosmetic reason.
When entire gland is diseased total thyroidectomy is a better
option.
Subtotal thyroidectomy is done depending on the amount of
gland involved, amount of normal gland existing and location of nodules—commonly done procedure in multinodular
goitre. Eight grams of thyroid tissue is retained in each lateral
lobe.
Often partial thyroidectomy or Hartley Dunhill operation
(isthmus + one entire lateral lobe and opposite side subtotal
Fig. 6.23: Multinodular goitre surgical specimen—total
thyroidectomy was done.
or partial) is also done depending on the amount of diseased
gland and normal tissues behind. Partial thyroidectomy is not
well approved now.
Postoperative L thyroxine is often given to prevent any
fluctuation in TSH level which may cause recurrent nodule
formation.
Prevention of multinodular goitre is possible by supple-
menting with L-thyroxine (0.1–0.2 mg) when patient
develops goitre in puberty. Formation of nodular goitre can be
prevented by correcting iodine deficiency by using iodine-rich
diet like eggs/seafood/milk or iodized salts and also avoiding
goitrogenic drugs and diet.
Suppressive dose of L-thyroxine alone may be used occasion-
ally in small nodules with limited results. TSH level should be
suppressed consistently below 0.5 mIU/L. Problems are need
of periodic monitoring with TSH estimation; hormone insensitive part of thyroid tissue continue to grow; indefinite period
of treatment; high recurrence after stopping L-thyroxine.
So it is not ideally accepted therapy. It is found that TSH
suppression is of no use in treating residual/recurrent MNG.
Note:
• Adequate thyroidectomy is essential, either total or subtotal, complete
removal of diseased thyroid without retaining is considered, in view
of chances of high recurrence in 10 or more years due to incomplete
removal. Re-surgery for recurrent M
ical plane and fibrosis; hence total thyroidectomy is often advised.
NG is difficult due to loss of anatom-
• Fine calcification is seen in papillary carcinoma (Psammoma bodies);
coarse calcification is seen in multinodular goitre.
• Radioactive iodine therapy may be beneficial after subtotal thyroidec-
tomy to prevent or treat recurrent nodules.
DISCRETE THYROID NODULE
Discrete thyroid nodule (4% of adult population) is a clearly
palpable nodule in thyroid. It can be solitary (isolated)
nodule (70%) if clinically only a nodule is felt without palpable
remaining gland OR it can be dominant nodule (30%) if
clinically a nodule is felt in a palpable remaining one or both
lateral thyroid lobes.
A discrete thyroid nodule is common in females. Discrete
nodule may be solid or cystic. USG, CT, MRI may confirm
the diagnosis.
15% solitary/isolated nodule may be malignant; 40% may be
follicular adenoma. Other causes are thyroid cyst, thyroiditis
or colloid degeneration.
Incidence of malignancy in dominant nodule is 50% less than
that of solitary nodule.
Risk factors for malignancy in discrete thyroid nodule are—
(1) solitary is 2 times more risk than dominant; (2) male is
4 times more than female (in solitary—48% to 12% in solid,
24% to 6% in cystic; in dominant 24% to 6% in solid, 12%
to 6% in cystic); (3) solid nodule is 2 times more risk than
cystic—Rule of 12.
453
CHAPTER 6 Thyroid
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SOLITARY THYROID NODULE
It is a single palpable nodule in thyroid on clinical examination,
in an otherwise normal gland. Rest of the gland is impalpable.
Current definition – A discrete lesion/nodule within the thyroid
gland that is palpably and or radiologically (Ultrasound neck)
distinct from surrounding thyroid parenchyma (in an otherwise
normal gland). The importance of thyroid nodule rests with the
need to exclude thyroid malignancy which occurs in 5–15% cases.
SRB's Manual of Surgery
A B
Figs. 6.24A and B: Solitary nodule thyroid in
one lateral lobe and isthmus.
Causes
Thyroid adenomas
Almost all thyroid adenomas are follicular. Follicular adenoma
can be – Colloid (do not have potential for microinvasion;
commonest type); Fetal (microfollicular – has potential for
microinvasion); Embryonal (atypical – has potential for micro-
invasion); Hurthle cell/oxyphil or oncocytic (has potential for
microinvasion); hyalinising trabecular adenoma.
Carcinomas – papillary (commonest carcinoma), follicular,
medullary (non-familial or familial or with MEN syndrome),
anaplastic.
Thyroid cysts.
Thyroiditis presenting as solitary nodule (localized form).
Note:
• Papillary adenoma earlier called, was actually papillary carcinoma;
papillary adenoma is very rare or probably non existing.
• Earlier definition was only clinically palpable nodule which also included
only palpable nodule in an underlying multinodular goitre (other nodules
are not palpable clinically) accounted for 50%; now radiological finding
is added to definition. Hence MNG cause is not considered.
Nodule is overactive. It is 5% common of which only 5%
can be malignant.
¾
Warm: Normally functioning nodule. Nodule and
surrounding normal thyroid will take up the isotope (active).
It is 10% common of which 10% can be malignant.
¾
Cold: Nonfunctioning nodule; may be malignant (need not
be always). Nodule will not take up isotope (underactive).
It is 80% common of which 20% are malignant.
Features
Single nodule palpable in one or other lobes of the thyroid
which is usually smooth and firm.
Lahey’s test does not show any other nodules in posterior
part of the gland.
Hot or warm in
99m
Tc scan but cold in I
nodule) commonly they are malignant.
Thyroid nodule in children and elderly can be malignant.
Rapid enlargement of thyroid nodule can be malignant.
Tracheal deviation towards opposite side is common–
confirmed by trail sign, three-finger test, auscultation and
X-ray neck.
30% of solitary nodules are cystic.
20% of cold nodules are malignant. Cold nodule may be
due to malignancy, thyroiditis, thyroid cyst or haemorrhage,
benign adenoma.
Commonest site of a nodule is at the junction of isthmus with
one of the lateral lobes.
Solitary thyroid nodule is the most common thyroid surgical
disease.
POSSIBLE FEATURES OF SUSPECTED MALIGNANCY IN
B
SOLITARY NODULE THYROID
x Any nodule can be malignant whether it is hard/ firm/cystic/small/
large/asymptomatic
x Rapid onset/rapid recent increase in size
x Hoarseness of voice/dysphagia/stridor/dyspnoea
x Fixity of the nodule
x Palpable significant neck nodes
x Nodule in a male patient
x Nodule in a child (50% are malignant)
x Nodule in extremes of age group
123
scan (discordant
SOLITARY NODULE IS ALSO CLASSIFIED AS
B
x Benign—70%
x Malignant—5%
x Indeterminate—10%—suspicious and follicular neoplasm
x Nondiagnostic—15%
Types
Based on function: (1) Toxic solitary nodule—3–5% of soli-
tary nodules of thyroid; (2) Nontoxic solitary nodule.
Based on radioisotope study (Technetium
scan):
¾
Hot: Means autonomous toxic nodule. Normal surrounding
thyroid tissue is inactive and so will not take up isotope.
99m
Pertechnetate
Fig. 6.25: Solitary nodule thyroid involving isthmus.
Investigations
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Ultrasound neck (very useful).
¾
It shows size, number, echogenicity, solid or cystic,
vascularity, presence of significant lymph node (irregular,
thick walled, without halo, more/chaotic vascularity,
absence of hilus, microcalcification, cystic/necrotic
changes).
¾
TIRADS—ACR 2015 (Thyroid Imaging Reporting And
Data System: American College of Radiology) based
on—(1) Composition (2) Echogenicity (3) Shape (4)
Size (5) Margin (6) Echogenic foci. TIRADS 1—Benign;
TIRADS 2—Not suspicious; TIRADS 3—Mildly suspicious; TIRADS 4—Moderately suspicious; TIRADS 5—
Highly suspicious.
¾
If sonologically, Nodule >1 cm with high suspicious of
malignancy or >1.5 cm with low suspicious of malignancy
or >2.0 cm with very low suspicious of malignancy needs
FNAC. Suspicion high (solid hypoechoic, irregular, microcalcification, taller than wide, extrathyroidal extension)
has got >90% malignant risk; intermediate (hypoechoic
solid but not other features) has 20% risk; low (iso- or
hyperechoic solid or partially cystic but no other features)
has 10% risk; very low (spongiform or partially cystic)
has got 3% risk.
¾
Irregular nodule, microcalcifications, taller than wide are
suspicious features for malignancy.
FNAC shows benign (70%); indeterminate (10%—it can be
suspicious or follicular neoplasm); malignant (5%); nondi-
indicates malignancy in that nodule. Malignant nodule shows
anarchical angiogenesis. Flow patterns are: Type 0 – no flow;
Type 1: only peripheral flow; Type 2: peripheral with small
central flow; Type 3: peripheral with extensive central flow;
Type 4: only central flow.
Serum calcitonin estimation if FNAC confirms medullary
carcinoma.
Thyroidal uptake on F18-fluorodeoxyglucose position emission
tomography (18FDGPET) scan is often useful in large nodule.
CT scan or MRI neck is not done routinely, but only in selected
cases. Large swelling/to see vascularity/retrosternal extension are the indications.
X-ray neck to see tracheal deviation.
A B
Figs. 6.27A and B: Trachea should be clinically examined to find out
whether it is central or deviated. In goitre involving both lobes, it is
central. One lateral lobe enlargement usually causes deviation of trachea
towards opposite side. Tracheal compression should be checked by
Kocher’s test. It confirms the scabbard trachea.
455
CHAPTER 6 Thyroid
Fig. 6.26: Solitary nodule thyroid.
agnostic (15%; reaspiration should be done in 4 weeks).
US-guided FNAC is the investigation of choice due to its
safety and accuracy.
T
, T4, TSH.
3
Radioisotope study (I
Power Doppler is done to know the vascularity of the gland.
123/I131/99m
Tc).
Vascularity is described in resistive index (RI) (Harley De
Nicola 2005). Normal RI is 0.65–0.7; if RI is more than 0.7 it
Note:
True incidence of solitary nodule will come down to 50% from its original
clinical diagnosis after investigations and surgical exploration.
Treatment
INDICATIONS FOR SURGERY IN SOLITARY NODULE
B
THYROID
x Malignant nodule
x Follicular neoplasm
x Toxic nodule in young
x Nodules with obstruction
Benign Nodule
Nontoxic benign nodule is treated with observation without
any therapy. There is no role of any hormone therapy (L
thyroxine). Annual clinical examination and ultrasound
neck is needed during essential follow up—any nodule
of 20% increase in size or more than 2 mm increase in
diameter warrants a repeat FNAC and hemithyroidectomy
(removal of entire one lateral lobe and entire isthmus) may
be considered. Compressive symptoms and cosmesis are
the indications for surgery—hemithyroidectomy.
x Recurrent cystic nodule
x Complex cyst (both solid and
cystic components)
x Cosmetic reason
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