Fig. 1.

The neoplasm, which was entirely submitted for histologic examination, demonstrated a variable growth pattern (Fig. 1A), with the predominant growth pattern being tubulopapillary with glomeruloid structures (Fig. 1B) although areas with a more glandular appearance and psammoma bodies were also present (Fig. 1C and D). Perineural invasion and lymphatic but not vascular invasion was identified. Immunohistochemical studies for keratins revealed the neoplastic cells to demonstrate strong diffuse cytoplasmic staining for pancytokeratin (Fig. 1E) and Cam 5.2 while being negative for cytokeratin 903 (CK34βE12). Stains for CK7 and CK20 demonstrated patchy strong cytoplasmic staining, with these antibodies appearing to recognize different subpopulations of neoplastic cells (Fig. 1F and G). A pax8 stain, which is reportedly positive in non-neoplastic rete testes, demonstrated patchy moderate staining of the neoplastic nuclei (Fig. 1H). Molecular studies using Therascreen KRAS and EGFR RGQ PCR kits (Qiagen) failed to reveal commonly encountered mutations in the KRAS and EGFR genes respectively.