Incidental and concurrent malignant lymphomas discovered at the time of prostatectomy and prostate biopsy: a study of 29 cases.

The incidence and histologic features of malignant lymphomas discovered at the time of prostate biopsy, transurethral resection, and prostatectomy are not well documented. We searched our surgical pathology files for malignant lymphomas identified from prostate surgical specimens from 1989 to 2004. Of 4,831 cases of prostate specimens (3,405 biopsies, 266 transurethral resections, 1,160 prostatectomies) examined at the City of Hope during this period, 29 cases of malignant lymphomas involving the prostate and pelvic lymph nodes were identified (0.6%). These malignant lymphomas can be divided into two groups: 1) 18 incidental cases (0.37%) without prior history of malignant lymphoma; and 2) 11 cases (0.23%) with concurrent known malignant lymphoma. For the first group, the patients with pelvic node involvement ranged in age from 59 to 78 years (mean, 69.2 years; median, 70 years), and the patients with prostate involvement ranged in age from 45 to 78 years (mean, 64.6 years; median, 67.5 years). For the second group, the patients ranged in age from 53 to 80 years (mean, 66.8 years; median, 69 years). Diagnoses of all cases were confirmed by immunohistochemistry or molecular analysis. Ten of 18 cases in the first group involved pelvic nodes only, and the other 8 cases were primary prostatic lymphoma. Of 18 cases in the first group, 13 were small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL), 3 were marginal zone B-cell lymphoma, and 1 was mantle cell lymphoma. These lymphomas were not readily apparent in most cases by histologic examination, and may be confused with chronic prostatitis when the prostate was involved or with reactive lymphoid hyperplasia when pelvic nodes were involved. Immunohistochemistry and molecular studies may be necessary to confirm the diagnosis. For the second group, prostate and pelvic lymph nodes were involved as part of systemic dissemination of concurrent malignant lymphoma. The diagnosis was usually easily established in these cases. Of 11 cases, 4 were SLL/CLL, 4 were follicular lymphoma, 2 were mantle cell lymphoma, and 1 was diffuse large B-cell lymphoma.