Context: Recent reports indicate the rate of primary testicular lymphomas is on the rise and misdiagnosis can still occur.
Objective: To review and investigate the clinicopathologic features of primary testicular lymphoma with emphasis on the differential diagnosis. Discussion about the issue of misdiagnosis is also presented.
Design: Retrospective review of pathology archives in 3 medical centers for cases fulfilling criteria of primary testicular lymphoma or paratesticular lymphoma was carried out. Clinicopathologic and immunohistochemical features were studied and analyzed.
Results: The search identified 34 cases. Patients ranged from 4 to 87 years of age (mean, 55 years). All presented with a testicular/paratesticular mass and were stage I. The masses ranged from 2.5 to 13 cm (mean, 5.6 cm). Microscopically, the tumors often had an intertubular growth pattern or diffuse arrangement of predominantly large cells with pleomorphic, twisted nuclei and small nucleoli. Mitotic activity was brisk and apoptotic bodies were abundant. Thirty-two tumors were classified as diffuse large cell lymphomas; immunophenotype was determined in 21 of these and all were of B-cell type. The median survival was 96 months. The rate of initial misdiagnosis was unexpectedly high (5 cases, 15%).
Conclusions: Most cases of primary testicular lymphoma fall into the broad category of diffuse large cell lymphoma and the majority are B-cell type with particularly high proliferative activity when characterized by appropriate immunophenotyping. Misdiagnosis can occur, especially in those cases in which presentation occurs at an age similar to that for germ cell tumors, showing the need for caution and appropriate immunostaining when a testicular neoplasm has an atypical appearance for a germ cell tumor.