Summary: Introduction

•The eyelids protect the eye from environmental insults and assist in keeping the cornea moist.

•Small growths in the tumor size can significantly derange tissue planes.

•A thorough understanding of the anatomy of this area is paramount to avoid permanently damaging vital structures.

27.1Introduction

The eyelid protect the eyes from environmental insults and assist in keeping the cornea moist. The tissue surrounding the eyelid is very thin, and consequently, small tumors can significantly derange tissue planes. To complicate matters, wide resections can have serious implications to the eye’s function. A thorough understanding of the anatomy of this area is paramount to avoid permanently damaging vital structures. Mohs micrographic surgery (MMS) is one technique used to remove tumors from this area. It offers advantages over other resection techniques in this area because it attempts to conserve tissue, and hence preserve function. It was originally for skin cancers in the periorbital region that the fresh frozen tissue technique detailed in Chap. 8 of this text became popular.

Summary: Review of the Relevant Anatomy

•The periorbital skin is one of the thinnest cutaneous surfaces of the body.

•The main function of the eyelid is to protect the eye from both desiccation and foreign matter.

•The orbital septum acts as a cover over the orbital contents and prevents the spread of cancer into these structures.

•The eyelid consists of two lamellae: the anterior lamella consists of skin and orbicularis

oculi muscle, and the posterior lamella consists of the tarsi and conjunctiva.

27.2Review of the Relevant Anatomy

At only 0.6 mm thick, the periorbital skin is one of the thinnest cutaneous surfaces of the body. The eyelids lack subcutaneous fat and the subcutaneous fascia is thinner than that found in the neck, thorax, and abdomen. The main function of the eyelid is to protect the eye from both desiccation and foreign matter. The eyelids assist in distributing lacrimal fluid across the eye’s surface to the medial canthus where it is collected into the nasolacrimal sac, then into the nasolacrimal duct, and finally into the nasal cavity. Each orbit is framed by the circular orbicularis oculi muscle. The eyelid, from superficial to deep, consists of the cutaneous surface, orbicularis oculi muscle, ciliary glands, palpebrae muscles, tarsal muscles and glands, and the palpebral conjunctiva. The orbital septum is a slender, fibrous, multilayered membrane that is considered the anterior orbital boundary and lies between the orbital rim and the tarsus, therefore serving as a barrier between the orbit and the lid. The septum thickens as it inserts onto the orbital rim. This thickening is referred to as the arcus marginalis. It inserts at about 3–5 mm above the tarsal plate. The orbital septum fuses with the capsulopalpebral fascia approximately 5 mm below the tarsus, and this common fascia inserts into the inferior tarsal angle in the lower eyelid. The orbital septum is found approximately at the same level as the tarsal muscles. It covers the orbital contents and acts as a barrier to prevent the spread of skin cancer into these strucutres. Fortunately, skin cancers tend to proliferate over it, rather than through it. From a surgical perspective, the eyelid consists of two lamellae. The anterior lamella consists of skin and orbicularis oculi muscle,

while the posterior lamella is comprised of the tarsi and conjunctiva [1].

Summary: Anatomical Considerations When

Using Mohs Micrographic Surgery in the

Periorbital Region

•The medial canthal area contains the draining system of the lacrimal apparatus and is a highly vascularized area; therefore, a cutaneous tumor has the ability to proliferate deeply in this area and cause significant impairment of the eye function.

•The patient’s eye must be protected at all times.

•Anesthetic eye drops are used along with eye shields whenever operating close to the eyeball itself.

•Due to the complex nature of surgery in the periorbital region, an oculoplastic reconstructive surgeon may be required to appropriately repair a Mohs defect.

Fig. 27.1 Application of lubricating eye drops prior to eye guard insertion

27.3Anatomical Considerations When Using Mohs Micrographic Surgery in the Periorbital Region

The medial canthal area is considered an embryonic fusion plane. Therefore, skin cancers have a propensity to proliferate deeply along that plane. The eye utilizes a specialized tearing system, which is located in the medial canthal area. Tearing fluid is produced in the lacrimal gland, which is located in the anterior upper temporal segment of the orbit and the superior conjunctival fornix. The tearing fluid is collected in the inferior medial puncta. From the puncta, the tearing fluid travels through the vertical canaliculi, then through the horizontal canaliculi to the common canaliculi and into to the lacrimal sac. From there, the fluid goes into the nasolacrimal duct and drains into the nose underneath the inferior turbinate. An invasive skin cancer can penetrate into these richly vascularized areas and damage tearing functions of the eyes.

Due to the complex nature of Mohs surgery of the eye, often times, an oculoplastic reconstructive surgeon is required to appropriately repair a Mohs defect. The patient’s eye must be protected at all times. Anesthetic

Fig. 27.2 Insertion of an eye shield used to protect the eye from unintentional injury

eye drops are used along with eye shields whenever operating close to the eyeball itself. A chalazion eyelid clamp may be useful to assist in electrocautery. Besides removing the tumor, the goals of eye surgery include maintaining visual acuity, tear flow, sufficient orbital lubrication, and minimizing corneal exposure [2, 3].

When performing Mohs surgery on the eyelid, it is important to use an eye guard to protect the eye itself. Additionally, care must be taken when using electrocautery so as not to transmit electricity through the eye guard. Lubricating eye drops should be used to protect the eye from injury secondary to the eye guard. (See Fig. 27.1). The eye guard should not be moved quickly when in place so that the conjunctiva and /or cornea is not injured. (See Fig. 27.2)

Summary: Periorbital BCC

•Basal cell carcinoma is the most common malignancy in the periorbital region and accounts for 90–95% of all periorbital malignancies.

•Although BCC is not likely to metastasize, it can locally grow large enough to destroy the eye, orbit, nose, and sinuses.

•The lower eyelid is the most common periorbital location for skin cancer.

•Dr. Mohs published the largest series using MMS to treat periorbital BCC: out of 1,124 cases of primary BCCs and 290 recurrent BCCs, 5-year cure rates were 99.4% and 92.4%, respectively.

•The other standard approach to removing periorbital BCC is conventional frozen section excision.

•Glatt and colleagues demonstrated a 99.2% clearance rate for periorbital BCC treated by conventional frozen excision with 3–4 mm margins taken during each stage involving 236 cases and a 5-year cure rate of 97.5%.

27.4Periorbital BCC

Basal cell carcinoma (BCC) is the most common malignancy in the periorbital region, accounting for 90–95% of all skin cancers in this region [4–6]. Periorbital BCC most commonly presents in patients during their sixth to eighth decades of life [7, 8]. Only 15% of periorbital BCC occurs in children or young adults. Although BCCs are not likely to metastasize, they can locally grow large enough to destroy the eye, orbit, nose, and sinuses [9].

The lower eyelid is the most common periorbital location for skin cancer [1, 10–13], with the medial canthus being the second most common location [11, 13]. It is hypothesized that the lower eyelid is the most common periorbital location for skin cancer because this area is exposed to a higher amount of ultraviolet radiation compared to other periorbital locations [11, 13].

Even after removing a BCC through Mohs surgery or conventional frozen excision, it can still recur. A number of BCC tumor characteristics are associated with recurrence including size >2 cm, prior recurrent

tumors, medial or upper eyelid location involvement, a history of radiation to the lesion, involvement of multiple eyelid segments, immunosuppression, ill-defined clinical borders, tarsal invasion, and invasion into the orbit, nose, or sinuses [5, 8, 14–18]. A number of histologic subtypes and tumor characteristics of periorbital BCCs are associated with a higher likelihood of recurrence including desmoplastic, basosquamous, keratotic, morpheaform, micronodular, multicentric tumors, and poorly differentiated tumors, as well as those with perineural invasion [3, 14, 15, 18, 19].

Dr. Mohs published the largest series using Mohs micrographic surgery (MMS) to treat periorbital BCC. Out of 1,124 cases of primary BCC and 290 recurrent BCCs, 5-year cure rates were 99.4% and 92.4%, respectively [11]. Periorbital BCCs less than 3 cm have 5-year cure rates of 97.5–100%, while BCCs greater than 3 cm have 5-year cure rates of 80% [11]. Dr. Mohs reported that lower eyelid BCCs have a 98.6% cure rate. Upper eyelid lesions clear 98.5% of the time, while medial canthus BCCs clear in 97.2% of cases, and lateral canthus BCCs are cleared 91% of the time. Remarkably, eyebrow lesions cleared 100% of the time [11].

Robins and colleagues used MMS on 631 cases of periocular BCC and reported a 98.1% success rate for primary lesions and a 93.6% for recurrent lesions [20]. Callahan and colleagues used MMS on 109 cases of periocular BCC and reported a 100% success rate. Drs. Monheit and Callahan demonstrated similar results as Drs. Mohs and Robins. Their study involved 283 cases of periorbital BCC tumors from a total of 315 periorbital cutaneous tumors treated by MMS. They reported that the 5-year cure rate was above 98% for all of the tumors combined [21]. Unfortunately, there was one fatality in their series from a metastatic BCC. In 2004, the Australian MMS database (the largest prospective database), part 1, looked at high-risk periocular BCC in 1,295 patients that were managed by MMS [22]. The most common reason for referral for MMS was the fact that the tumor was located in a periocular area (55%) [22]. Twenty-four percent of the patients were referred because of recurrence, which was the second most common reason for referral [22]. The most common site for periocular BCC was the medial canthus or lower eyelid [22]. Those on the lower eyelid were more common in males, and those on the medial canthus more common in females [22].

Patients with lower eyelid BCC were older than those with medial canthus BCC (the mean difference was 4.7 years) [22]. The most common histologic subtypes were nodulocystic and infiltrating (34.8%). The majority of the lower lid tumors were infiltrating BCCs, and the majority of the upper lid and medial canthus tumors were nodulocystic BCCs [22]. Infiltrating BCCs were significantly larger than nodulocystic or superficial subtypes, and as a consequence, had larger defect sizes [22]. Twelve cases (1%) had histologically confirmed perineural invasion [22]. Seven of these were medial canthal and five were lower eyelid BCCs [22]. Interestingly, there was no association between tumor size and site. In this study, 32% of the periocular tumors were recurrent, and of these, the superficial BCCs were more likely to be recurrent [22]. Compared to the primary BCCs, these recurrent tumors were larger in size and resulted in larger defects as well [22]. Out of the 415 recurrent BCCs, only 15/415 cases had recurred after primary MMS, of which 7/15 had undergone MMS only. There was no association between the site of the tumor and the number of levels required for complete excision, although morphea BCCs and recurrent cases required more levels, as did recurrent cases [22]. The Mohs surgeon managed 915/1,295 cases. Out of the remaining 380 cases referred for repair, 314 were managed by an oculoplastic surgeon and 63 by a plastic surgeon. It was noted that after 1996, there was an increase in the referrals to oculoplastic surgeons instead of plastic surgeons [22].

The Mohs Australian database, part 2, included a 5-year follow-up of 819 patients treated by MMS for periocular BCC [23]. Forty-two percent had a 5-year follow-up, and out of these, 2% had recurrences [23]. All of these 7/346 patients with recurrences had been previously recurrent, with up to three recurrences before MMS had been performed. As noted above, prior recurrence was the main predictor of recurrence following MMS, as were infiltrating and superficial histologic subtypes [23].

The other standard approach to removing periorbital BCC is by conventional frozen section excision. Glatt and colleagues demonstrated a 99.2% clearance rate for 236 cases involving periorbital BCC treated by conventional frozen excision with 3–4 mm margins taken during each stage [24]. Out of the 236 patients, 81 were followed for 5 years, and the 5-year cure rate was 97.5% [24]. Older and colleagues reported a 100%

success rate with conventional frozen section control in 113 cases [25].

Nemet et al. investigated 485 cases of periocular BCC and SCC [26]. BCCs were surgically excised with 3 mm, and SCCs with a 5 mm margin. Frozen section or MMS were used for incompletely excised cases and those located in the medical canthus or close to the lacrimal drainage system [26]. Excision was incomplete in 54.4% of the cases, and 84.6% chose to have reexcision guided by either frozen section or MMS and 10.6% chose radiation therapy [26]. Patients with morpheaform-type BCC had a significantly higher rate of incomplete excision compared with nodulartype BCC (43.6–23.5%, respectively) [26]. The rate of incomplete excision was also significantly higher at the medial canthal region compared with other tumor locations [26]. Notably, there were no recurrences in any of the 19 cases in which MMS technique was used for reexcision compared to 4.7% recurrences in which frozen section was used [26]. The average time to recurrence was reported to be 32 ± 17 months [26].

Summary: Periorbital SCC

•The second most common periorbital malignancy is squamous cell carcinoma, accounting for approximately 5–10% of all periorbital malignancies.

•Similar to BCC, SCC also presents more commonly on the lower eyelid but not to the same extent as BCC.

•Periorbital SCC metastatic rates have been reported to be as high as 21%.

•Factors which are associated with a higher rate of periorbital SCC metastasis include: perineural invasion, recurrence following treatment, large tumor size, and poor differentiation.

•Dr. Mohs used MMS for 213 cases of periorbital SCC and reported an overall 98.1% 5-year cure rate. Primary periorbital SCCs had a 98.5% cure rate versus 95.8% for recurrent SCCs.

•Using conventional surgical excision, the recurrence rate is approximately 18% for periorbital SCC.