Managing Periocular Skin Malignancies with Mohs Micrographic Surgery

Traditionally, the gold standard for treatment of periocular skin malignancies has been complete surgical excision regardless of tumor type (Ophthalmology. 2001;108:2088-2100). This works well in cases where a central eyelid tumor is well circumscribed. In these instances, the oculoplastic surgeon can accomplish the primary excision and closure. However, for the poorly defined tumor, particularly one overlying the medial or lateral canthal tendon where deep orbital extension is possible, care must be taken to control the surgical margins with permanent serial excisions or frozen section margins in order to reduce the recurrence rates of certain malignancies.

This latter approach has 2 drawbacks. First, frozen section controlled excision requires the coordination of 2 physicians—the surgeon and the pathologist—and unless the orientation of the excised tissues is standardized with that of the surgeon, pathologists may experience difficulties. Mohs micrographic surgery (MMS) addresses the shortcomings of surgical excision with frozen section control by allowing one physician (Mohs-trained dermatologist) to perform the excision in a standardized approach and interpreting the specimens in one location.

The Evolution of Mohs Micrographic Surgery (MMS)

Fredrick Mohs first developed MMS in the 1930s. Originally, tissues were fixed in situ with zinc chloride or another fixative, and serial shave biopsies were performed until the entire tumor was removed. Since then, the technique has progressed to the point where fresh tissue is color-code mapped and excised. Any remaining tumor is then serial mapped, sectioned, and frozen-fixed until the site is tumor free.

MMS has an excellent track record for excision of basal cell carcinomas. Malhotra et al reported 5-year recurrence rates in 890 basal cell carcinoma patients of 2% (Ophthalmology. 2004;111:631-636). Among the 7 cases of recurrence, 5 were located in the medial canthus, and all were previously recurrent cases. The same researchers also reported excellent results with periocular squamous cell carcinoma. Only 2 out of 79 patients experienced a recurrence (3.64%) (Ophthalmology. 2004;111:617-623).

There have also been reports of successful excision of sebaceous gland carcinoma (J Am Acad Dermatol. 1986;14(4):668-673). However, because this tumor is quite rare, a large series has been unavailable for study. Nevertheless, sebaceous gland carcinoma can spread intraepithelially (pagetoid spread) and may be more amenable to excision using serial, permanent-sectioned surgical margins, a technique known as slow Mohs (Eye. 2004;18(8):854-855). Excision of these tumors should be accompanied by conjunctival map biopsies to delineate any conjunctiva spread across the ocular surface or to the other eyelid. Pigmented lesions, lentigo maligna, and melanoma, cannot be excised by MMS, since freeze-fixation depigments tissue. Therefore, slow Mohs should also be used on these tumors.

MMS and Its Aftermath

MMS is performed by fellowship-trained dermatologists on patients who are usually under local anesthesia. Depending on the invasiveness of a tumor, excision may take a few hours to half a day. After complete excision, reconstruction can be performed later that day or on subsequent days. Since MMS attempts to preserve non-tumor involved tissue, malignancies excised with this technique leave defects which are often partial thickness or smaller in size than traditional excisional techniques with empiric surgical margins,which allow for more tissue to reconstruct a defect.

Eyelid defect closure should address both posterior lamella (tarsus and conjunctiva) and anterior lamella (skin and orbicularis) deficiencies. Partial thickness defects can be primarily closed or left to heal with granulation tissue. Small defects can be closed with primary closure or by releasing canthal tendons to recruit tissue. Larger defects may require flaps (tarsoconjunctival grafts and skin-muscle flaps) or grafts (free tarsal, full thickness skin, or composite eyelid grafts) to close a defect. All closures should avoid vertical tension on the eyelid, since this may cause eyelid malposition or ectropion.

References

Author Disclosure

The author states that he has no significant financial relationship with the manufacturer or provider of any product or service discussed in this article or with the manufacturer or provider of any competing product or service.