Abstract:

Metastatic thyroid carcinoma involving the skin is very rare and may herald aggressive disease. We report a case of metastatic papillary thyroid carcinoma to the skin, following surgical and radiation treatment of the primary tumor. A 56 year old male presented with a 3 cm, painful, subcutaneous nodule located on his left upper medial thigh. His past medical history was significant for papillary thyroid carcinoma with subsequent metastasis to the right neck. Prior treatment included thyroidectomy and radiation. An excisional biopsy of the new left thigh lesion was performed. Histologically, there was a large nodular mass extending into the dermis and upper subcutis. Sheets, islands and cords of malignant cuboidal epithelial cells were present with intervening thick collagen bundles. The malignant cells demonstrated a high nuclear: cytoplasmic ratio, mitotic figures, and nuclear chromatin clearing with margination (“Orphan Annie” nuclei). There were also numerous micro follicles with central colloid. The TTF-1 immunohistochemical stain was positive, supporting the diagnosis of metastatic papillary thyroid carcinoma. This case exemplifies a rare but clinically significant metastatic behavior of papillary thyroid carcinoma to the skin. Recognition of the histopathologic and immunohistochemical features of cutaneous metastatic thyroid carcinoma is important to enable further treatment, such as molecular targeted therapy.

Financial Disclosure:
No current or relevant financial relationships exist.

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Matthew Bak