By Lynn McCain 
 

One of the key qualities of expert pathologists is that they learn to expect the unexpected. In the Michigan Medicine Department of Pathology, our pathologists and collaborators recently reported on some of these unexpected findings.

Mixed epithelial and stromal tumors (MESTs) are rare, usually benign tumors that are typically found in the kidney in perimenopausal women. These tumors can clinically mimic malignant tumors, so accurately identifying them is essential. Most of the time, these tumors are found incidentally, but some patients will present with abdominal or flank pain.

Imagine their surprise when Drs. Elaina Daniels, Resident, and Dr. Rohit Mehra, from Pathology, reviewed a case where they identified a MEST – but it was not from a perimenopausal female’s kidney. It was from a 52-year-old male’s prostate. This patient had surgery for prostate adenocarcinoma, and on pathologic evaluation, they discovered the MEST. Together, Daniels and Mehra identified four cases of MEST in the male reproductive tract. These cases were also reviewed with Dr. Kyle Perry, who practices in the field of soft tissue pathology. A literature review uncovered an additional 24 cases reported since the 1940’s.

“This study expands our understanding of a group of rarely reported tumors-incidental/early MEST of the efferent testicular-ductular system of the genitourinary tract. Such tumors are uncommon in efferent testicular-ductular system, where they may arise from and develop under aberrant hormonal influences or altered hormonal milieus.  These tumors are benign; however, they may pose diagnostic challenges for the surgical pathologists, and a better recognition of such entities helps avoid misidentification and mismanagement of such tumors,” said senior author Dr. Rohit Mehra.

To help others recognize that MEST does occur in men and outside the kidney, they published these cases in Pathology – Research and Practice. By sharing unexpected pathological findings, these pathologists support their colleagues worldwide and helping them expect the unexpected.

 

 

 

 

Citation:

Daniels E, McKenney J, Al-Ahmadie H, Perry K, Mehra R. Incidental early mixed epithelial and stromal tumor of the efferent testicular-ductular system of the genitourinary tract: A small case series with literature review. Pathology – Research and Practice (2025) 268:155797. https://doi.org/10.1016/j.prp.2024.155797.