Malignant lymphomas involving the prostate. A study of 13 cases.

The clinical and pathologic findings in 13 cases of malignant lymphoma involving the prostate gland were reviewed. The lymphomas tended to occur in elderly men with a mean age of 60 years (range, 30-86 years) and were clinically manifested by prostatic enlargement with urinary obstruction. In only one of the patients was there clinical suspicion of lymphoma before surgery. Seven patients had primary extranodal lymphoma of the prostate, with a variety of histologic subtypes, including small cell lymphocytic (one patient), diffuse small cleaved cell (two patients), diffuse mixed small and large cell (two patients), diffuse large non-cleaved cell (one patient), and high-grade diffuse small non-cleaved cell (undifferentiated non-Burkitt's) (one patient). At the time of presentation, none of these patients had hepatosplenomegaly, inguinal lymphadenopathy, abnormal complete blood counts, or elevated serum acid phosphatase levels. Six other patients with previously documented malignant lymphoma at other sites had prostatic involvement 2 to 60 months (mean, 14 months) after the primary diagnosis. Histologically, these secondary prostatic lymphomas included diffuse small cleaved cell (two patients), diffuse mixed small and large cell (one patient), diffuse large non-cleaved cell (two patients), and large cell immunoblastic, polymorphous type (T-cell by immunotyping) (one patient). The mean survival was 14 months for all patients (range, 2-44 months), with no apparent difference between primary and secondary involvement. One patient remains alive 44 months after secondary prostatic involvement with diffuse large non-cleaved cell lymphoma. Although malignant lymphomas involving the prostate are rare, they should be included in the differential diagnosis of lower urinary tract obstruction, particularly in patients with a previous history of lymphoma.