Low-grade lymphoma of mucosa-associated tissue in the parotid gland: a case report of fine-needle aspiration cytology diagnosis using flow cytometric immunophenotyping.

A 66-year-old woman with Sjögren's syndrome for 7 years presented with an enlarged right parotid gland. The left parotid gland, which showed myoepithelial sialadenitis (MESA), had been resected 4 years earlier. A fine-needle aspiration (FNA) biopsy of the right parotid gland was performed. Examination of the smears revealed cells of intermediate size with a round-to-irregular nuclear outline and distinct pale cytoplasm intermixed with small mature round lymphocytes. The chromatin was slightly paler and less clumped than in small mature lymphocytes. A small inconspicuous nucleolus was seen in most of the cells. Flow cytometry immunophenotyping performed on the FNA biopsy material showed a monoclonal population of B cells with kappa light chain restriction. The cytomorphology coupled with the immunophenotyping study in this clinical context suggested the diagnosis of low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT). Extensive staging work-up revealed no evidence of disseminated disease. The right parotid gland was surgically excised. Histology and gene rearrangement studies confirmed the cytologic diagnosis. To our knowledge, this is the first description of a low-grade lymphoma of MALT in a salivary gland to be diagnosed by FNA.