Melanotic medullary carcinoma of thyroid – report of a rare case with brief review of literature

BACKGROUND Melanin production in medullary carcinoma is extremely uncommon. CASE PRESENTATION We report a rare variant of medullary carcinoma of thyroid with melanin production in a 52-year-old woman who presented with swelling in the thyroid of 3 months duration. This tumor recurred thrice in two years after surgery and patient died with metastasis. Microscopic examination showed typical morphology of medullary carcinoma with numerous cells loaded with melanin pigment as confirmed by bleached Fontana-Masson, negative iron and immunohistochemical stains. Tumor cells were diffusely immunopositive for calcitonin, HMB-45, chromogranin, synaptophysin, CEA but showed focal paranuclear dot positivity for cytokeratin. No C-cell hyperplasia was seen in the adjacent thyroid gland. Nature of the pigment was further confirmed on ultra structural examination. CONCLUSION Melanotic medullary carcinoma is an extremely uncommon entity. There is a need to report more number of cases in the literature for exact categorization and prognostication of this subtype of medullary carcinoma.