[Szpiczak plazmocytowy tarczycy - opis przypadku].

Unlabelled: Extramedullary plasmacytoma (EMP) is the localized plasma cell neoplasm, that arise in tissues other than bone. The upper respiratory tract and the oral cavity are the most common sites for EMP location. EMPs of the thyroid gland are extremely rare and thus little is known about their behavior compared to other EMPs.

Case Report: 68-year-old female patient was admitted to the Department of General, Gastroenterological and Endocrine Surgery due to suspicion of neoplastic proliferation of unknown character within the thyroid gland. Computed tomography (CT) of the neck and chest showed tumor modeling adjacent anatomical structures. Cytological presentation obtained by fine needle aspiration biopsy was classified as category V according to the Bethesda system ("suspicious for malignancy"). The recognition of the lymphoma was suggested. The histopathological examination result of the specimens obtained from surgical biopsy was ambiguous. The patient was transferred to the Neurosurgical Department to continue the diagnostic process due to a presence of tumor within Th5 vertebral body. Percutaneous biopsy and magnetic resonance imaging (MRI) was performed, revealing metastatic character of the lesion and presence of plasma cells. After transferring patient back to surgical ward thyroidectomy was performed. Postoperative histopathological and immunohistochemisty analysis revealed EMP with highly immature morphology. Afterwards patient was admitted to Hematology Clinic in order to establish an adjuvant therapy.

Conclusions: EMP is a very rare form of the primary thyroid malignancy, what makes it difficult to recognize. However, in the differential diagnosis of the thyroid tumors, EMP should be always considered.