A case report of an uncommon sex-cord stromal tumor consisted of luteal and sertoli cells in a spayed bitch.

We report a rare case of benign sex cord-stromal tumor consisted largely of luteoma with minor portion of Sertoli cell tumor located at the position of the left ovary excision in an 11-year-old ovariectomized bitch. Granulosa cell component was lacking, and both luteal and Sertoli cell portions were entirely positive for inhibin alpha and neuron-specific enolase, whereas luteoma portion alone was positive for Wilms' tumor-1 (WT1), immunohistochemically. The results suggest that this tumor is a possible complication of incomplete ovarian excision at the time of ovariectomy and consisted of uncommon hybrid of luteal and Sertoli cells to be diagnosed as an unclassified sex cord-stromal tumor if applied in human cases. WT1-expression pattern suggested the signature of the difference in the phenotype of these cell types.