Mammary-type myofibroblastoma of the psoas.

Mammary myofibroblastoma is a rare, benign, mesenchymal neoplasm that was first described in the breast in 1987. However, extra-mammary-type myofibroblastoma (MTMF) was not described until 2001 as a distinct entity. We report a case of extra-MTMF arising from the retroperitoneum, which was encountered in our clinic. We also completed a review of the literature using PubMed in patients with extra-MTMF.