Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT): a challenge for clinicopathological diagnosis.

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is an extremely aggressive ovarian tumor, with a poor prognosis and high mortality for young women. This paper aims to inform clinical physicians of new clinical improvements and further understanding of SCCOHT. Two cases diagnosed with SCCOHT from our medical database were reconfirmed and immunohistochemically stained with vimentin, CK, EMA, S-100, ER, PR, and SMARCA4. Diffuse small, round cells with scant cytoplasms, small nucleoli, hyperchromatic nuclei, and active nuclear divisions were detected in the microscopy. The immunohistochemical markers indicated minor positive but notably were SMARCA4 negative, which led to the final diagnosis. SCCOHT is a rare and lethal ovarian tumor in young women. The loss of SMARCA4 or the presence of SMARCA2 is a specific marker for the disease. Susceptibility to CDK4/6 inhibitors associated with downregulation of SMARCA4 targeted cyclin D1 may be a probable therapeutical mechanism for the disease.