Primary endobronchial histiocytic sarcoma in a case of papillary carcinoma thyroid: a complex clinical scenario.

Histiocytic sarcoma is a rare malignant neoplasm showing histiocytic differentiation. We document a case of a 55-year-old man presenting with cough and breathlessness following a subtotal thyroidectomy for infiltrating papillary thyroid carcinoma. An endobronchial growth was seen on endoscopy. Histopathologic examination revealed a neoplasm of histiocytic lineage with positivity for leucocyte common antigen, Vimentin, CD68, CD4, and CD45RO. To the best of our knowledge, primary endobronchial histiocytic sarcoma in association with infiltrating papillary thyroid carcinoma has not been reported in the literature so far. Our case emphasizes the importance of clinicopathologic and radiologic correlation in resolving difficult diagnostic dilemmas.