Persistent Müllerian Duct Syndrome on 18 F-FDG PET/CT.

A 32-year-old man presenting with limb weakness was diagnosed with Guillain-Barré syndrome. Abdominal distension was noted, and imaging revealed a large, heterogeneously enhancing abdominopelvic mass with bilateral cryptorchidism and uterine-like tissue. The mass showed high FDG uptake on 18 F-FDG PET/CT, while the uterine-like tissue did not. Following surgical biopsy, histopathologic examination demonstrated seminoma and rudimentary uterine tissue, confirming persistent Müllerian duct syndrome (PMDS). PMDS is a rare autosomal recessive disorder characterized by male phenotype with cryptorchidism and persistent Müllerian structures. Imaging for cryptorchidism in children can help establish the diagnosis, allowing timely surgical intervention to prevent malignant transformation.