Inhibin-alpha, CD99, HEA125, PLAP and chromogranin immunoreactivity in testicular neoplasms and the androgen insensitivity syndrome

We investigated 115 testicular and 3 epididymal tumors and 6 cases of the c omplete androgen insensitivity syndrome (AIS) for the expression of inhibin -alpha, CD99, HEA125, PLAP, and chromogranin, using monoclonal antibodies a nd standard immunhistochemical techniques. Inhibin-alpha was detected in th e neoplastic cells in 27 of 27 primary Leydig cell tumors (LCTs), 1 of 1 me tastatic LCT, 6 of 20 Sertoli eel tumors (SCTs), 4 of 5 juvenile granulosa cell tumors (JGCTs), and 2 of 5 unclassified sex cord-stromal tumors (USCST s). Except for 2 choriocarcinomas, the choriocarcinomatous component of 1 m ixed germ cell tumor, and a small focus of inhibin-positive syncytiotrophob last in 1 embryonal carcinoma, inhibin-alpha immunoreactivity was not prese nt in the neoplastic cells of the 38 remaining testicular germ cell tumors; 11 B-cell and 1 T-cell lymphomas; 1 granulocytic sarcoma; and 1 rhabdomyos arcoma of the testis; 1 adenoma of the rete testis, and 3 adenomatoid tumor s of the epididymis. Inhibin-alpha immunoreactivity was present in the Sert oli cells and Leydig cells in 5 testicular hamartomas and in 1 Sertoli cell adenoma in 6 cases of AIS; both Sertoli and Leydig cells were also positiv e in the extranodular testicular parenchyma present in 2 of these cases. CD 99 was detected in 10 of 15 primary LCTs, 1 of 7 SCTs, 3 of 5 JGCTs, and in 1 of 5 USCSTs but was not found in any tumor outside the sex cord-stromal category. HEA125 immunostaining was not detected in sex cord-stromal tumors ; however, 3 of 12 seminomas, 3 of 12 embryonal carcinomas, 6 of 8 yolk sac tumors, and 1 of 2 teratomas were HEA125 positive. PLAP was not detected i n sex cord-stromal tumors except for 4 of 15 primary LCTs but was present i n most germ cell tumors. Chromogranin immunostaining was present in the sex cord-like element in 1 of 5 USCSTs, 1 of 8 YSTs, 1 of 2 teratomas, and in 1 of 1 rete adenoma, and in normal adjacent rete testis. In conclusion, alt hough inhibin-alpha and PLAP, and, to a somewhat lesser extent, CD99 and HE A125 immunostaining are helpful in the differential diagnosis of certain te sticular neoplasms that are difficult to distinguish on morphologic grounds , chromogranin is far less helpful in this context. Copyright (C) 2000 by W .B. Saunders Company.