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Surgical Management of Subungual Melanoma: A Single Institution Experience of 124 Cases
Jesse T. Nguyen, M.D., Karim Bakri, M.D., Emily C. Nguyen, M.D., Craig H. Johnson, M.D., Steven L. Moran, M.D..
Mayo Clinic, Rochester, MN, USA.
To characterize subungual melanoma and determine optimal surgical management.
Methods: Our institution’s tumor registry was reviewed for all cases of subungual melanoma treated surgically. Amputation level, Breslow depth, and sentinel lymph node biopsy (SLNB) were examined and compared with outcome. Survival rates were estimated using Kaplan-Meier method.
During a 96-year period, 124 cases were identified. There were 65 males and 59 females. Mean age at diagnosis was 58. The most common presenting symptoms were pigmentation and nail plate changes. Mean length of symptoms before diagnosis was 2.2 years. Seventy-nine lesions occurred on the hand and 45 on the foot. The thumb was the most common appendage affected (33.8%) followed by the great toe (25.0%). Initial clinical involvement was local in 104 patients (83.9%), with in-transit metastasis identified in 1 (0.8%), regional nodal metastasis in 16 (12.9%), and distant metastasis in 16 (2.4%). Mean follow-up time was 9.4 years.
Histological subtype was available in 86 patients, the most common being nodular melanoma (34.9%), acral lentiginous (32.6%), and superficial spreading (23.2%). Histologic invasion was Clark IV or V in 68.6% of patients. Average Breslow depth was 3.1 mm in 76 patients. Mean Breslow depth in the hand was 3.56 mm compared 2.44 mm in the foot (p=0.50). Breslow thickness ≥ 4 mm was significantly associated with a poorer recurrence-free survival (p<0.001) and disease-specific survival (p<0.008).
Surgical treatment involved amputation (93.5%) and local excision (6.5%). Amputation level varied and was surgeon dependent. Amputations of the thumb most commonly occurred at the proximal phalanx or MCP joint (43.9%), hallux at the proximal phalanx or MTP joint (69.0%), finger at the middle phalanx or PIP joint (39.4%), and lesser toe at the metatarsal (53.8%). Increasing amputation levels were not significantly associated with disease recurrence, death from any cause, or death from disease.
SLNB was performed in 20 patients; 5 were positive (25.0%). SLNB was not associated with disease progression (p=0.44), death from any cause (p=0.99), or death from disease (p=0.40).
Disease progression occurred in 61 patients (49.2%). Local progression was seen in 11 (18.0%), in-transit progression in 6 (9.8%), regional nodal progression in 38 (62.3%), and distant metastasis in 26 (42.6%). Recurrence-free survival rates at 5, 10, 15, and 20 years were 57.1%, 49.9%, 47.0%, and 44.4%, respectively. Fifty-three patients died of melanoma-related causes. Disease-specific survival rates at 5, 10, 15, and 20 years following surgery were 59.3%, 49.3%, 45.2%, and 45.2%, respectively. Overall survival rates at 5, 10, 15, and 20 years were 60.5%, 43.8%, 33.1%, and 28.3%, respectively.
Conclusion: The diagnosis of subungual melanoma is often delayed. The level of amputation does not influence survival or outcome once histological free margins are obtained. Efforts should be directed at functional reconstruction especially for the thumb, the most common appendage affected in our series. SLNB may not offer a survival advantage and future studies are required. Currently we recommend elective lymph node dissection for positive SLNB and palpable nodes. We emphasize early biopsy of subungual pigmented lesions and surgical treatment with conservative amputation.
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