Melanin production in medullary thyroid carcinoma

Abstract

A case of melanin‐producing medullary thyroid carcinoma is reported in a 51‐year‐old man. Histologically, the tumour had a typical pattern of medullary thyroid carcinoma with numerous scattered pigmented cells which contained large amounts of melanin pigment as confirmed by bleached Fontana‐Masson stain. Immunohistochemical staining revealed positivity of almost all tumour cells for calcitonin and chromogranin, whereas S‐100 protein and HMB‐45 staining was positive only in the pigmented tumour cells. This finding confirms the ability of medullary thyroid carcinoma cells to have multidirectional differentiation, although melanocytic differenciation remains an exceptional phenomenon.