Aims: Small cell carcinoma of the ovary, hypercalcaemic-type (SCCOH) is morphologically similar to small cell carcinomas from other sites. The aims of this study were to (i) determine if a biomarker panel would distinguish small cell carcinomas of the ovary, cervix (SCCCx) and lung (SCCLu) and (ii) potentially determine the histogenesis of SCCOH.
Methods and results: Nine ovarian small cell carcinomas (seven hypercalcaemic type; two pulmonary type), eight SCCCx and 22 SCCLu were immunostained for thyroid transcription factor (TTF)-1, WT-1, p16, cKIT and OCT3/4; a subset of cases were tested for human papillomavirus (HPV). WT-1 was diffusely positive in 6/7 SSCOH versus two of 33 other small cell carcinomas (P <or= 0.001). TTF-1 was diffusely positive in 20/22 SCCLu and 1/8 SCCCx, and negative in all SCCOH. p16 and cKIT demonstrated variable patterns of immunoreactivity in all cases. HPV was identified in 5/6 SCCCx; SCCOH and SCCLu were negative for HPV.
Conclusions: Combined staining with WT-1 and TTF-1 will distinguish SCCOH from SCCLu and SCCCx with a sensitivity of 86% and specificity of 97%. HPV is specific for tumours of cervical origin, but p16 immunohistochemistry is not useful for this purpose. The presence of diffuse WT-1 supports a Müllerian origin for SCCOH, whereas the absence of cKIT and OCT3/4 argues against a germ cell origin.