Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue with plasma cell differentiation: Periodic acid-schiff reaction-positive Dutcher body is a diagnostic clue to distinguish it from plasmacytoma.

We herein report a case of primary parotid extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) with Dutcher bodies. An 82-year-old man presented with a 4 cm × 2.5 cm mass in the left parotid region. Positron emission tomography/computed tomography (PET/CT) showed localized abnormal fluorodeoxyglucose (FDG) uptake in the left parotid gland and lymph nodes of the left cervical region. Fine needle aspiration (FNA) cytology of the left parotid gland showed lymphoplasmacytoid cells with periodic acid-Schiff (PAS)-positive Dutcher bodies. A subsequent excisional biopsy showed sheets of small- to medium-sized neoplastic B cells with abundant IgM in the cytoplasm as detected by immunohistochemistry. A diagnosis of stage II MALT lymphoma was made, but the patient did not receive therapeutic intervention. As previously reported, Dutcher bodies are mainly observed in B-cell neoplasms with IgM production. Because these characteristic intranuclear inclusions can be easily observed by PAS staining, the presence of PAS reaction-positive Dutcher bodies in FNA cytology can serve as a clue to differentially diagnose MALT lymphoma from plasmacytoma. Diagn. Cytopathol. 2017;45:547-551. © 2017 Wiley Periodicals, Inc.