Primary anaplastic large cell lymphoma of the testis.

Anaplastic large cell lymphoma (ALCL) was first described by Stein et al. in 1985, at that time neoplastic cells were labeled by the monoclonal antibody CD30. ALCL was included as a differentiate entity in the reviewed Kiel and REAL classification. ALCL carries the t (2; 5) (p23; q35) translocation; the absence of ALK kinase from normal lymphoid cells indicates that immunohistochemical expression of ALK is specific for the (2; 5) translocation. This disease is characterized by a diffuse proliferation of large anaplastic cells with kidney-shaped/horse-shoe nuclei. A distinguishing feature is a perinuclear eosinophilic region that represents a prominent Golgi apparatus. These cells are named hallmark-cells being almost pathognomonic. Immunohistochemically the most important features are that tumor cells consistently express CD30 and EMA on the cell membrane and in the Golgi region, while ALK immunostaining is usually both, cytoplasmic and nuclear. To our knowledge only two cases of primary ALCL of the testis have been reported. Hereby we present a case of a typical ALCL expressing ALK and CD30, which presented with subcutaneous nodules and bilateral testicular mass, without systemic involvement.