Cutaneous Metastases of Malignant Melanoma: A Clinicopathologic Study of 192 Cases With Emphasis on the Morphologic Spectrum

Abstract

Metastatic melanoma represents one of the most common types of cutaneous metastases. In up to 5% of patients, metastatic melanoma can be the first manifestation of the disease. For the most part, the histologic diagnosis of metastatic melanoma poses little diagnostic difficulty; however, some metastases may adopt unusual or unfamiliar appearances mimicking other benign and malignant conditions. We present a study of 192 cases of cutaneous metastatic melanomas with special emphasis on their spectrum of morphologic features. The patients were 115 men and 77 women, 23-91 years of age (mean 57 years). Most tumors were located on the proximal legs, scalp, and arms and ranged from 0.8 to 3.0 cm. One hundred ten cases showed the classic morphologic appearance of melanoma (well-circumscribed epithelioid dermal/subcutaneous nodule), 82 cases showed unusual histologic appearances that mimicked other benign and malignant neoplasms. In 16 patients (8.3%), there was no evidence of primary melanoma and the cutaneous metastasis was the only manifestation of the disease. The histologic diagnosis of cutaneous metastatic melanoma can pose difficulties for diagnosis, especially in the face of an unknown primary neoplasm. Unusual features observed in this series included examples of cutaneous metastatic melanoma that closely simulated metastatic carcinoma, dermatofibroma, leiomyosarcoma, angiosarcoma, nevoid melanoma, halo nevus, blue nevi, and atypical fibroxanthoma. Several cases also showed rhabdoid, balloon cell, and alveolar features. Immunohistochemical stains plus careful clinical history helped to establish the correct diagnosis. Our series illustrates that the differential diagnosis of cutaneous metastatic melanoma can be broad and difficult. To the best of our knowledge, this is the largest series of cutaneous metastatic melanomas reported in the literature.

Sinonasal blue naevus: case report and clinicopathological review

“…12 Sinonasal melanomas are also uncommon lesions, constituting less than 1 per cent of all melanomas and less than 4 per cent of all sinonasal tumours. 3 They are generally larger tumours with symptoms including epistaxis.…”

Cutaneous malignant melanoma in an 11-month-old Russian blue cat

“…Cutaneous malignant melanomas in humans frequently metastasise to the skin (Martinez and Young 2008). These metastases are typically well-circumscribed dermal or S/C nodules that are difficult to differentiate from additional primary melanomas (Zbytek et al 2008;Plaza et al 2010). The second melanoma in the case presented here developed without any evidence of metastasis or local recurrence 4 months after the initial melanoma had been excised.…”

Spindle cell melanocytic lesions: part II—an approach to intradermal proliferations and horizontally oriented lesions

“…Definitive junctional nesting or lentiginous growth must be observed to indicate primary disease. Metastatic disease typically shows a nodular pattern with the epicentre of the nodule present in the deep dermis or subcutaneous tissue 22 83. Deep-seated metastatic lesions also give an impression of ‘upward growth’, with the superficial edge appearing infiltrative or expansile and compression/stretching of overlying structures.…”

“…Often there is geographic central necrosis. Surrounding vascular space invasion, particularly when extensive, is further evidence suggestive of metastatic disease, although angiolymphatic invasion may be seen in primary disease as well 22 82 83. Primary melanomas show a more superficial epicentre and give an impression of ‘downward growth’ of the lesion.…”