Tumor-to-tumor metastasis with endometrial carcinoma metastatic to squamous cell carcinoma of vulva: the first reported case.

Endometrial carcinoma metastasizing to the vulva is a rare occurrence, with only 15 reported cases in the literature. To our knowledge, no cases of tumor-to-tumor metastasis involving endometrial carcinoma as a donor tumor have ever been published. We report the first case of an endometrial carcinoma as a donor tumor metastasizing to a squamous cell carcinoma of the vulva, a recipient tumor. A 79-year-old woman with a history of endometrioid adenocarcinoma of the uterus presented with a vulvar lesion. Pathologic examination of the excised lesion confirmed the presence of metastatic endometrioid adenocarcinoma; however, it was found within a well-differentiated squamous cell carcinoma of the vulva. Surrounding the squamous cell carcinoma was a background of a high-grade vulvar intraepithelial lesion (vulvar intraepithelial neoplasia 3), and immunohistochemistry confirmed the presence of 2 separate tumors involved in a tumor-to-tumor metastasis. This unique case highlights the importance of awareness of the phenomenon, and expands the current spectrum of tumor-to-tumor metastases.