In humans and canines, the morphology of
granulosa cell tumors is extremely variable and causes diagnostic difficulties. In human pathology, immunohistochemistry has been widely used for the diagnosis of
granulosa cell tumors, whereas, limited studies are present in canine species. The aim of this study was to investigate the expression of cytokeratins,
vimentin, and
inhibin-alpha in canine normal ovaries, epithelial ovarian
tumors, and
granulosa cell tumors to establish an immunohistochemical panel for the differential diagnosis of ovarian
tumors.
Formalin-fixed,
paraffin-embedded tissue sections from 4 normal ovaries, 8
granulosa cell tumors, and 6 epithelial ovarian
tumors (2
adenomas and 4
adenocarcinomas) sections were obtained and stained with
hematoxylin and
eosin and immunohistochemically for
cytokeratin AE1/AE3,
cytokeratin 7,
vimentin, and
inhibin-alpha. In normal ovaries,
cytokeratin 7,
cytokeratin AE1/AE3, and
vimentin were expressed in the surface epithelium. Granulosa cells were negative for
cytokeratin 7 and displayed variable expression of
vimentin,
cytokeratin AE1/AE3, and
inhibin-alpha toward follicular maturation.
Granulosa cell tumors were negative for
cytokeratin 7 and positive for
inhibin-alpha. Conversely, ovarian epithelial cells
tumors were positive for
cytokeratin 7 and negative for
inhibin-alpha. Both granulosa and epithelial cell
tumors displayed variable expression of
vimentin.
Cytokeratin AE1/AE3 was expressed by all epithelial-derived
tumors and 6 of 8
granulosa cell tumors. The results of this study suggest that useful immunohistochemical markers to distinguish epithelial ovarian
tumors from
granulosa cell tumors are
cytokeratin 7 and
inhibin-alpha.