A 68-year-old man presented with bilateral inguinal lymphadenopathy without any other clinical symptoms. Complete blood count was normal with no notably abnormal circulating cells. Fine-needle aspiration (FNA) assessment of the lymph node revealed a monomorphic population of medium- to large-sized cells with regular or sometimes irregular nucleus outline; coarse chromatin, sometimes with nucleoli; and a slight to moderately abundant amount of basophilic cytoplasm containing red to dark-red granulations in the majority of the cells (panel A). This cytomorphologic appearance looked consistent with T-cell or natural killer–cell lymphoma, yet the examination of the lymph node biopsy revealed small-sized cells with nodular pattern. Using the immunohistochemical stains, these cells were positive for CD20, CD5, BCL2, IgD, and Cyclin D1, without CD10 or CD23 expression (panels B-C [courtesy of Julien Moroch]), hence the diagnosis of mantle cell lymphoma.

Although mantle cell lymphoma is known to have many morphologic features like classic small- to medium-sized lymphoma cells, blastoid cells, pleomorphic cells, large cells, or even Burkitt-like cells, the granular lymphoid cells seen in our case are rare. Yet these latter were demonstrated here as part of B-cell lineage.