Cytopathologic findings in histiocytic sarcoma of thyroid mimicking as anaplastic carcinoma: A report of a rare case with review of literature

Abstract

Background Histiocytic sarcoma is an extremely rare malignant hematological histiocytic neoplasm which is a diagnosis of exclusion based on its morphological and predominantly immunohistochemical criteria. Case Description and Diagnosis A 63‐year female presented with complaints of a midline neck swelling along with right sided neck swelling. On fine‐needle aspiration (FNA) from the thyroid lesion and the right cervical lymph node, the smears showed similar findings and a provisional morphological diagnosis of malignant spindle cell neoplasm was kept. On immunohistochemistry, the tumor cells showed immunoreactivity for vimentin, CD45, CD 68 and fascin and were immunonegative for thyroglobulin, S100, CD21, CD3, CD4 and other markers. Based on the immunohistochemical profile, a diagnosis of histiocytic sarcoma was established. Conclusion Histiocytic sarcoma is a rare malignant neoplasm that can be easily missed in thyroid resembling an anaplastic carcinoma.