Primary testicular diffuse large B-cell lymphoma: A case report focusing on touch imprint cytology and a non-germinal center B-cell-like phenotype.

Primary diffuse large B-cell lymphoma (DLBCL) of the testis is a rare subtype of testicular tumor. While the histomorphology of testicular DLBCL is well described, a paucity of information in the literature exists with regard to the cytological diagnosis of this subtype of tumor. Touch imprint specimens were obtained from a testicular DLBCL occurring in a 64-year-old man. The cytological features of imprints were compared with the results obtained from histological and immunohistochemical examinations. Smears obtained from the touch imprints exhibited a high cellular yield consisting of discretely arranged monomorphic large cells with irregular nuclear membranes, scant cytoplasm and conspicuous nucleoli. Histologically, the tumor consisted of discohesive neoplastic lymphocytes that infiltrated diffusely and produced a wide separation of intact seminiferous tubules. Diffuse, intense immunostaining for CD45, CD20, MUM1 and Ki-67 led to the diagnosis of primary DLBCL of the testis with a non-germinal center B-cell-like phenotype. Careful observation of the touch imprint specimens of testicular DLBCL revealed a high cellularity with a predominant single-cell pattern of monomorphic cells demonstrating irregular nuclear membranes and conspicuous nucleoli. In addition, DLBCL is capable of developing in the testis and forming a predominantly discohesive cell population, suggesting the presence of a lymphoid malignancy. Thus, it may be possible to detect morphological features that are characteristic of DLBCL using imprint cytology. To the best of our knowledge, this is the first study reporting the diagnosis of testicular DLBCL using touch imprint cytology.