Immunohistochemistry:
Both benign and malignant GCTs typically stain positively for S-100, a neuromelanocytic marker and for CD68 a marker of lysosomal activity. GCTs also stain positive for neuron-specific enolase, CD57, inhibin, calretinin, TFE3, SOX10, CD56, PGP9.5, and vimentin [11,14,33-36]. S-100 is strongly positive for GCT but is not specific since it can be seen in melanoma, micro glandular adenosis, and typically negative in breast carcinomas [11]. Some GCT have been described in pregnancy [37] and the immunohistochemical profile shows no hormonal dependence. GCTs lack estrogen or progesterone receptor and cytokeratin expression [14]. Microscopically, GCTB can resemble apocrine carcinoma, but GCTB lacks androgen receptors and apocrine carcinoma lacks S100 expression. AE1/3 epithelial markers can also help distinguish GCTB from invasive carcinoma because they stain negative in GCTB [14].