Immunohistochemistry may be useful to rule out morphological differential diagnoses other than sex cord–stromal tumors, including sex cord-like endometrioid carcinoma of the ovary (EMA+, ER+, PR+, PAX8+, inhibin−, calretinin−), carcinoid tumors since only 12% are EMA + (chromogranin+, synaptophysin+, calretinin−, inhibin−, WT1−, SF1−), and FATWO in a subset of cases (admixture of other architectural patterns, CK7+, androgen receptor+, Glutathione S-transferase+) [8,150,155,156,157,158]. The gene discussed is CALB2; the disease is carcinoid tumor.