Mullerian choristoma in a case of spinal dysraphism

It is extremely rare to find mullerian choristomas in association with spinal dysraphism, with <10 cases published in English literature. We report a case of heterotopic uterus and fallopian tube-like tissue within a lumbar subcutaneous lipoma associated with spina bifida and tethered cord. A 21-year-old lady presented with lumbar swelling since birth and dull pain in the lower back. Magnetic resonance imaging showed spina bifida at level L3 and L4, tethering of the cord and a subcutaneous lipomatous swelling. Biopsy revealed lobules of fibroadipose tissue embedded in which were seen organoid cystic structures containing prominent smooth muscle coats in their wall. These cystic structures were lined by the endometrium and showed fallopian tube-like papillary infoldings. Immunohistochemistry showed estrogen receptor positivity in the epithelium, stroma, and smooth muscles. The epithelial cells were also positive for cancer antigen 125 and cytokeratin 7 while the stromal cells showed CD10 positivity, supporting mullerian derivation. The pathogenesis and differential diagnosis of such lesions is discussed.