Oncocytic metaplasia occurring in melanoma

Abstract

BACKGROUND: Oncocytosis is a cellular feature characterized by the presence of a finely granular eosinophilic cytoplasm due to the accumulation of mitochondria. While this histologic trait can be found in normal tissues, it is also seen pathologically as a degenerative phenomenon. We recently reviewed a spectrum of oncocytic melanocytic nevi that did not have clinical significance. We now describe similar changes in melanoma. METHODS: We retrospectively reviewed 12 melanomas noted to have prominent granular eosinophilic cytoplasm and completed ultrastructural studies. We obtained patient histories and clinical follow-up information from the patients' physicians. RESULTS: All cases were primary melanomas and showed prominent oncocytosis in the majority of the lesional melanoma cells. Oncocytosis was observed in both melanoma in situ and invasive melanoma with a wide range of Breslow thicknesses (range, 0.45-5.05 mm). It occurred in the presence and absence of ulceration, regression, vascular invasion, and brisk tumor infiltrating lymphocytes. Ultrastructural studies revealed melanocytes with numerous distorted mitochondria. CONCLUSION: Melanoma is capable of presenting in a variety of histologic guises, including oncocytic change. While our observations are preliminary, this pathologic curiosity likely represents a degenerative phenomenon of little prognostic importance.