Histopathology 2000, 37, 323±331 Secondary neoplasms of the male genital tract with different patterns of involvement in adults and children N Dutt, A W Bates & S I Baithun Department of Histopathology and Morbid Anatomy, Institute of Pathology, The Royal London Hospital, London, UK Date of submission 6 January 2000 Accepted for publication 27 April 2000 Dutt N, Bates A W& Baithun S I (2000) Histopathology 37, 323±331 Secondary neoplasms of the male genital tract with different patterns of involvement in adults and children Aims: The incidence, presentation and macroscopic and histological features of secondary neoplasms of the male genital tract are described with reference to their differential diagnosis. Methods and results: A retrospective study of cases from the Royal London Hospital yielded a total of 31 secondary neoplasms involving the testis: 14 at post- mortem examination and 17 surgical specimens. Nine cases were leukaemias: six acute lymphoblastic and two acute myeloid leukaemias in children, and one chronic lymphocytic leukaemia in an adult. The commonest primary sites of metastases to the testis were prostate (six cases), stomach (five cases) and lung (three cases). There were two malignant melanomas and isolated examples of metastases from the adrenal gland (neuroblastoma), cerebellum (medulloblastoma), soft tissue (alveolar rhabdomyosarcoma), pancreas and rectum. Of the metastases from solid tumours, 12 involved the right testis only, three involved the left and four were bilateral. In seven of these cases there were multiple testicular nodules, in seven there was a single mass, and in the rest there was diffuse involvement. Secondary neoplasms represented 4.6% of all testicular neoplasms at autopsy, and 1.6% in surgical specimens. There were five secondary penile neoplasms: two each from the pancreas and prostate and one from the bladder. Two neoplasms metastatic to the spermatic cord, both from a gastric primary, were included in the series. Conclusions: Secondary neoplasms of the testis occur with a frequency comparable to other sites in the genitourinary tract, and metastases to the spermatic cord, epididymis, and penis, are rare in comparison. Disseminated neoplasms rarely present initially at this site and are histologically distinctive in adults, but in children they must be distinguished from primary small round blue cell tumours. Keywords: metastasis, penis, secondary tumour, spermatic cord, testis Introduction Data on the incidence, presentation and histological appearances of secondary tumours of the genitourinary tract are potentially useful for the interpretation of biopsy material. In the genitourinary tract the propor- tion of secondary neoplasms is relatively low: 2.3% of biopsied bladder neoplasms are secondary, 1 and these may mimic the histological appearances of primary neoplasms; 2 while 3% of renal neoplasms biopsied are of secondary origin. 3 The incidence of secondary neoplasms of the testis has been reported at 0.02% 4 to 2.5% 5 of all autopsies (including non-neoplastic deaths), and a review in 1992 revealed a total of over 200 cases in the literature. 6 Most of these are from autopsy material and a clinical first presentation of disseminated malignancy with a testicular mass is very rare. 7 Almost all secondary testicular tumours are metastases from distant primary sites, of which lung, prostate and gastrointestinal tract are the common- est. 4,8±10 Metastases to the spermatic cord and epididymis are even less frequent, with some 42 q 2000 Blackwell Science Limited. Correspondence: Dr S I Baithun, Department of Histopathology and Morbid Anatomy, Institute of Pathology, The Royal London Hospital, London E1 1BB, UK.