Track

Abstract

Cutaneous metastasis from thyroid carcinoma is rare and usually occurs in the setting of disseminated disease. Scalp is the most common site for cutaneous metastases with papillary carcinoma being the most common primary (41%), followed by follicular (28%), medullary and anaplastic (15% each). An 81-year-old male non-smoker presented with a rapidly growing right scalp papule measuring 1.5 x 1.2 cm. Past medical history was significant for multiple myeloma and metastatic thyroid cancer status post thyroidectomy 16 years ago. Prior histology of thyroidectomy specimen revealed a poorly differentiated insular variant with areas of anaplastic dedifferentiation and metastasis to the left lung, left sub-pectoral region, liver and L5 lumbar spine. The patient was treated with carboplatin and paclitaxel and received radiotherapy. Histology of scalp mass showed ulcerated epidermis with sheets and nodules of markedly atypical cells in the dermis showing nuclear pleomorphism and numerous atypical mitoses. Papillary architecture, pseudo vascular spaces and extravasated red cells were present focally, raising the possibility of angiosarcoma. Other differential diagnoses included Kaposi sarcoma, melanoma and poorly differentiated squamous cell carcinoma. The tumor was positive staining for TTF-1 and negative for CD34, ERG, CD31, HHV-8, p40, melan-A, and D2-40 (Fig 1). Ki-67 proliferation index was >90%.  This case report highlights a rare event of poorly differentiated thyroid carcinoma metastasizing to the skin. A high index of suspicion may prompt immunohistochemical analysis and the request for a complete clinical history, ultimately preventing misdiagnosis.