MELANIN PRODUCTION IN MEDULLARY-THYROID CARCINOMA

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