Completely Regressed Cutaneous Melanocytic Lesion Revisited

Dramatic clinical appearance of a “halo” of depigmentation, in this case surrounding an extensively regressed primary melanoma discovered during physical examination of a patient referred for treatment of an “unknown primary” melanoma metastatic to the ipsilateral inguinal lymph nodes. (Photograph courtesy of Bruce Redman, DO, University of Michigan Multidisciplinary Melanoma Clinic, Ann Arbor, MI.)

Positron emission tomography scan/computed tomography scan obtained approximately 4 years after the report of trauma-induced regression of a pigmented lesion on the posterior calf. There was no evidence of hypermetabolic activity anywhere in the lower leg (not shown), but there is extensive glucose-avid adenopathy in the groin.

Punch biopsy of scar on posterior calf approximately 4 years after the patient reported trauma-induced regression of a progressively enlarging pigmented lesion at that site. At low power (not shown), the biopsy demonstrated a broad zone of dermal pigment deposition, while at higher power, fibrosis, angioplasia, and melanin-laden macrophages are evident (hematoxylin & eosin, original magnification 400×). Immunohistochemical stains for S-100 and Melan-A failed to demonstrate definitive evidence of malignancy.

(A) Histologic appearance of a halo nevus showing a dense lymphocytic infiltrate surrounding and focally infiltrating dermal nests of small, benign-appearing melanocytes (arrow; hematoxylin & eosin, original magnification 200×). (B) Histologic appearance of a recurrent nevus following an incomplete shave biopsy, showing rare melanocytes within an area of fibrosis and associated lymphocytic infiltrate. Note that the pattern of fibrosis is parallel to the epidermal surface, and is more orderly in appearance than usually seen with regressing lesions (hematoxylin & eosin; original magnification 400×.

A 63-year-old woman presented for evaluation of a completely regressed melanocytic lesion on the right upper chest. Histologic evaluation could not determine if this represented regression of a melanoma or a benign nevus, and there was no clinical evidence of residual, recurrent, or metastatic melanoma. The patient provided this photograph of the lesion's appearance approximately 1 year earlier—the irregular shape and pigmentation suggest the possibility that this indeed represented a melanoma, and re-excision of the site was performed.