Cutaneous regressing/regressed malignant melanoma: a clinicopathologic analysis of 8 cases

Abstract

To study the clinicopathologic features and differential diagnosis of cutaneous regressing/regressed melanoma. Histopathologic evaluation and immunohistochemical study by EnVision method were performed in 8 cases of cutaneous regressing/regressed melanoma. The clinical presentation, treatment and follow-up data were analyzed. The age of the patients ranged from 40 to 69 years (mean 58 years). The male-to-female ratio was 3: 1. Tumors were located on the back (4 cases), sole of the foot (2 cases), ventral aspect of the toes (1 case), and the forearm (1 case). Clinically, 6 patients presented with progressive black mole of the skin, followed by subsequent focal hypopigmentation, even scarring. Two patients presented with multiple foci of dark-brown pigmentation. Microscopically, 3 cases were completely regressed malignant melanoma. Tumoral melanosis was found in 1 of 3 cases. The other 5 cases were melanoma with severe regression. The extent of regression ranged from 75% to 90%. The Breslow depth of the tumors ranged from 0.5 to 1.0 mm. Immunohistochemically, both metastatic and primary tumor cells were diffusely positive for S-100, HMB45 and Melan A, while melanophages were positive for CD68. Follow-up data were available in 8 patients, ranging from 8 to 27 months. Five patients were alive with no evidence of disease, 1 patient was alive with stable disease and 2 patients died of metastatic melanoma. Correlation between clinical presentation and pathologic features is important for diagnosis of cutaneous regressing/regressed melanoma. Thin melanoma with extensive regression ( ≥ 75%) should not been regarded as low metastatic risk and wide excision combined with sentinel lymph node biopsy is recommended.