EBV-positive plasmacytoma of the submandibular gland--report of a rare case with molecular genetic characterization

Abstract

Plasmacytomas are differentiated plasma cell tumors that present as a mass lesion in osseous or extraosseous sites. Although the most common site for extramedullary plasmacytomas (EMP) is in the upper respiratory tract, plasmacytomas initially presenting as salivary gland masses are very uncommon. We describe a case of an EBV-positive plasmacytoma presenting as a 7.7 cm submandibular mass in an elderly immunocompetent man which displayed an abundance of "naked nuclei" on fine needle aspiration cytology. The tumor showed lambda light chain restriction and positive expression for CD38, MUM1 and EBER. Subsequent investigation for myeloma revealed absence of M-protein and end-organ damage, except for a lytic lesion in the radial bone. An extensive fluorescent in situ hybridization analysis showed the tumor to be negative for the t(4;14) FGFR3/IGH translocation as well as translocations involving the IGH, IGL, IGK, CCND1, BCL2, BCL6 and C-MYC genes. KRAS genetic analysis did not reveal any mutations of codons 12, 13 and 61.

Fig. 1

FNA cytology showing abundant bare nuclei with condensed chromatin in a vague cartwheel-like pattern (×600)

Fig. 2

a Cut section of gross specimen showing a pale fleshy tumor. b Residual salivary gland tissue (arrow) is focally present (Hematoxylin and Eosin)

Fig. 3

a Neoplastic plasma cells infiltrate the salivary gland tissue. Note residual ducts to the right (×100). b Confluent sheets of plasma cells with varying degrees of low-grade atypia is present. No overt plasmablastic features are identified (×400). c Strong CD38 immunohistochemical and d EBER in situ hybridization positivity (×400)