A case of thyroid MALT lymphoma with extreme plasma cell differentiation

Abstract

Background : In comparison with other MALT lymphomas, MALT lymphomas of the thyroid gland and skin show more pronounced plasma cell differentiation. We report a case of thyroid MALT lymphoma with extreme plasma cell differentiation.

Case : An 80-year-old man presented to us with a mass in the right anterior neck, and fine needle aspiration cytology of the thyroid and the right cervical lymph node ware performed. The fine needle aspiration cytology showed atypical cells with eccentric nuclei, eosinophilic cytoplasm and clear cell boundaries, and atypical cells with granular cytoplasm and indistinct cell boundaries, respectively. The atypical cells showed a cartwheel chromatin pattern, alveolar structure and rosette-like arrangement. These cytological findings led to the suspicion of a neoplastic lesion with proliferation of plasmacytoid cells. Therefore, thyroid biopsy was performed, which revealed dense and diffuse proliferation of plasmacytoid cells. The results of immunohistochemistry ware as follows : CD10−, CD20+/−, CD79a+, CD138−, CD56−, Kappa+, Lambda−, IgG4−, CEA−, Calcitonin−. From these findings, the lesion was diagnosed as a MALT lymphoma of the thyroid gland.

Conclusion : Histology and immunohistochemistry are important to confirm the diagnosis of MALT lymphoma. Further, clinical findings and other laboratory results may be required. Therefore, it is important to predict MALT lymphoma with extreme plasma cell differentiation in fine needle aspiration cytology.