Mohs micrographic surgery (MMS) is a specialized surgical technique for the treatment of melanoma and nonmelanoma skin cancers (NMSCs).1-3 The procedure involves surgical excision, histopathologic examination, precise mapping of malignant tissue, and wound management. Indications for MMS in skin cancer patients include recurring lesions, lesions in high-risk anatomic locations, aggressive histologic subtypes (ie, morpheaform, micronodular, infiltrative, high-grade, poorly differentiated), perineural invasion, large lesion size (>2 cm in diameter), poorly defined lateral or vertical clinical borders, rapid growth of the lesion, immunocompromised status, and sites of positive margins on prior excision. The therapeutic advantages of MMS include tissue conservation and optimal margin control in cosmetically or functionally sensitive areas, such as acral sites (eg, hands, feet, digits).1,3
The intricacies of the nail apparatus complicate diagnostic biopsy and precise delineation of peripheral margins in digital skin cancers; thus, early diagnosis and intraoperative histologic examination of the margins are essential. Traditionally, the surgical approach to subungual cutaneous tumors such as melanoma has included digital amputation4; however, a study of the treatment of subungual melanoma revealed no difference in survival based on the level of amputation, therefore advocating for less radical treatment.4
Interestingly, MMS for cutaneous tumors localized to the digits is not frequently reviewed in the dermatologic literature. We present a retrospective case series evaluating the clinical outcomes of digital melanoma and NMSCs treated with MMS.
Methods
A retrospective chart review was performed at a private dermatology practice to identify patients who underwent MMS for melanoma or NMSC localized to the digits from January 2009 to December 2014. All patients were treated in the office by 1 Mohs surgeon (A.H.) and were evaluated before and after MMS. Data were collected from the electronic medical record of the practice, including patient demographics, histopathologic diagnosis, tumor status (primary or recurrent lesion), anatomic site of the tumor, preoperative and postoperative size of the lesion, number of MMS stages, surgical repair technique, postoperative complications, and follow-up period.
Results
Twenty-seven patients (13 male, 14 female) with a total of 28 lesions (malignant melanoma or NMSC) localized to the digits were identified (Table). The mean age at the time of MMS was 64.07 years. Twelve (42.86%) patients were 70 years of age or older, 11 (39.29%) were between 50 and 69 years, and 5 (17.85%) were younger than 50 years. Fifteen (53.57%) of the lesions were localized to the fingers, and 13 (46.43%) were localized to the toes; 18 (64.3%) of the lesions were distal and 10 (35.7%) were proximal to the distal interphalangeal joint. The most common pathologic diagnosis was squamous cell carcinoma (SCC) in situ (12/28 [42.86%]), followed by melanoma in situ (6/28 [21.42%]), severely dysplastic nevus (4/28 [14.29%]), SCC (4/28 [14.29%]), acrospiroma (1/28 [3.57%]), and melanoma (1/28 [3.57%]).
Surgical techniques used for repair following MMS included xenograft (10/28 [35.71%]); split-thickness skin graft (7/28 [25.0%]); secondary intention (4/28 [14.29%]); flap (4/28 [14.29%]); full-thickness skin graft (2/28 [7.14%]); and complex closure (1/28 [3.57%]). Clinical preoperative, operative, and postoperative photos from Patient 21 in this series are shown here (Figure). Two patients required bony phalanx resection due to invasion of the tumor into the periosteum: 1 had a malignant melanoma (Breslow depth, 2.52 mm); the other had an SCC. In addition, following removal of a severely dysplastic nevus, debulked tissue revealed melanoma in 1 patient.
Primary subungual melanoma of the right distal great toe in an 80-year-old man at presentation (A); following Mohs micrographic surgery (B) and repair with a full-thickness skin graft (C); and at 6 weeks’ (D) and 18 months’ (E) postsurgical follow-up.
Postoperative complications were noted in 4 (14.29%) of 28 MMS procedures, including bacterial wound infection (3.57%), excess granulation tissue that required wound debridement (7.14%), and delay in wound healing (3.57%). Follow-up data were available for 25 of the 28 MMS procedures (mean follow-up, 35.4 months), during which no recurrences were observed.