Seminoma Arising From an Intra-abdominal Testis in a Phenotypic Female With Complete Androgen Insensitivity Syndrome (CAIS): A Rare Case Report From a South Indian Tertiary Cancer Centre.

Complete androgen insensitivity syndrome (CAIS) is a rare X-linked disorder, which is present in genetically confirmed males who exhibit female phenotypic characteristics. In this case, an intra-abdominal testis, which subsequently transformed into a malignant germ cell tumor, is a rare malignant evolution that is infrequently reported in phenotypically female patients.  A South Indian origin, 41-year-old phenotypic female with untreated primary amenorrhea presented with progressive abdomino-pelvic distension. MRI imaging demonstrated a large pelvic mass with retroperitoneal lymphadenopathy; biopsy confirmed dysgerminoma with elevated beta-human chorionic gonadotropin (β-hCG) and lactate dehydrogenase (LDH). She completed neoadjuvant bleomycin, etoposide, and cisplatin (BEP) chemotherapy followed by cytoreductive surgery, which revealed intra-abdominal testes with a complete pathological response, and subsequent karyotyping confirmed a 46,XY pattern consistent with CAIS. Malignant transformation of intra-abdominal testicular tissue in a phenotypically female patient is exceptionally rare and emphasizes the critical importance of early diagnosis; a proper treatment regimen is warranted to improve patient care.