Soft Tissue, Adenomatoid tumour

Adenomatoid tumour is a benign neoplasm of mesothelial origin. It is typically composed of tubules, microcystic spaces, and vascular-type slits and is lined by bland cuboidal to flattened mesothelial cells. Stromal lymphocytes may also be present. Although this lesion is more commonly found in the uterus, it is the most frequently encountered benign neoplasm of the fallopian tube. Typically, this lesion is seen in a subserosal location though can be located elsewhere.

Grossly, this lesion tends to be small, well circumscribed but unencapsulated, and yellow-gray in colour. The differential diagnoses are adenocarcinoma (particularly at frozen section), lymphangioma, and leiomyoma. Useful immunohistochemical stains which are positive in this tumour are LMWK, WT1, and calretinin.