Paracicatricial melanocytes as a sign of melanoma.

Intradermal melanocytes in the setting of melanoma represent a diagnostic challenge to dermatopathologists as their presence may represent superficially invasive melanoma vs benign nevus cells or reactive dermal melanocytes. Previous dermatologic literature suggests that the absence of cytologic atypia in intradermal melanocytes and their presence in nonmelanocytic neoplasms lends to their characterization as reactive, benign, melanocytic proliferation. A 67-year-old female presented for evaluation of a 10-mm irregularly pigmented dark brown macule on the left cheek. Initial shave biopsy showed transected malignant melanoma measuring at least 0.6 mm in thickness. Multiple reexcision specimens demonstrated residual melanoma with banal appearing intradermal epithelioid melanocytes within and surrounding the scar. The melanocytes tracked into the skin graft, which had previously been free from involvement. Positron emission tomography-computed tomography (PET CT) and lymph node biopsies did not show evidence of metastatic melanoma. Ten months after her diagnosis and following five surgical excisions, the patient was diagnosed with metastatic melanoma to the brain and succumbed to intracranial hemorrhage. We present a case in which paracicatricial melanoma may simulate benign paracicatricial melanocytic hyperplasia. These findings have significant therapeutic and prognostic implications for the practicing dermatologist and dermatopathologist.

Unusual Case of Nail Unit Melanoma.

We present a case of a nail unit melanoma with chondroid differentiation that was initially misdiagnosed as a benign chondroid neoplasm. A 67-year-old Caucasian woman presented to an outside dermatologist with a tender subungual nodule on the right index finger with overlying nail plate changes that had been present and enlarging for 1 year. Initial histopathological evaluation rendered a diagnosis of benign chondroid neoplasm. On arrival to our institution, magnetic resonance imaging was performed, and the lesion appeared consistent with a glomus tumor. Plastic surgery performed a surgical resection with intraoperative frozen sections revealing a hypocellular cartilaginous mass, but pathology was unable to comment on the presence of malignant cells. On permanent sectioning of the excised lesion, a lentiginous proliferation of melanocytes overlying a dermal aggregate of atypical cells with conspicuous mitoses embedded in a chondroid matrix was seen. A panel of immunohistochemical stains was performed, including SOX-10, HMB-45, S-100, MITF and MART1 was performed with SOX-10, HMB-45, and S-100 staining the junctional melanocytes and dermal cells, rendering a diagnosis of primary chondroid melanoma.