Retiform Sertoli-Leydig cell tumours: clinical, morphological and immunohistochemical findings.

AIMS To determine the morphological and immunohistochemical profile of retiform Sertoli-Leydig cell tumours and to compare the observed profile with that of adult rete ovarii. METHODS AND RESULTS Nineteen retiform Sertoli-Leydig cell tumours were studied, eight by immunohistochemistry, and five examples of rete ovarii from adult females were also evaluated immunohistochemically. The patients ranged in age from 3 to 74 years with a mean age of 31 years. Four patients were virilized and had an abdominal mass; two were virilized with amenorrhoea and two had amenorrhoea alone. Eight presented with an abdominal mass and one patient was pregnant. Two tumours were incidental findings. Information on stage was available in 16 patients: 14 tumours were stage 1, one was stage 2, and one was stage 3. Fifteen tumours were of intermediate differentiation and four were poorly differentiated. Papillary structures were evident grossly in four cases. Microscopically, all cases had a retiform pattern in addition to varying quantities of sex cord, gonadal stromal and heterologous elements. Heterologous elements were present in 13 cases and consisted of hepatocytes (n = 7), mucinous epithelium (n = 7) and skeletal muscle (n = 2). Immunohistochemical evaluation of eight tumours showed a more intense positivity for keratin in the retiform areas, whereas the gonadal stromal component had a more intense expression of inhibin. Inhibin stains Leydig cells strongly and hepatocytes moderately. Rete ovarii epithelium was positive for keratin and vimentin in the five cases studied, and for inhibin in one case. Follow-up was available on 13 patients. Three tumours behaved in a malignant fashion: one each was stage 1, 2, and 3 at diagnosis. CONCLUSIONS Immunohistochemistry is useful in distinguishing retiform Sertoli-Leydig cell tumours from other tumours that they may resemble. Inclusion of inhibin is essential in a panel of antibodies to evaluate these tumours. The clinical behaviour of these neoplasms cannot always be predicted from their morphology or clinical stage.