Synchronous Thyroid Involvement in Plasma Cell Leukemia Masquerading as Hashimoto's Thyroiditis: Role of Ancillary Cytology Techniques in Diagnostic Workup.

Neoplastic plasma cell involvement of thyroid is an uncommon condition, and it may involve thyroid in multiple myeloma or solitary plasmacytoma. Its clinical and pathological features are not well understood. We present a rare case of synchronous thyroid involvement in plasma cell leukemia presenting as thyroid nodule with primary hypothyroidism. Simultaneous cytology, immunocytochemistry, FISH analysis with 13q14.3 and TP53 on cytology smears and haematology workup were performed to diagnose and to understand disease pathobiology with poor outcome.