40 Giant Cystic Adenomatoid Tumor of the Uterus: A Comprehensive Case Study of Uncommon Presentation of 15 cm Tumor with Predominant Cystic Growth Pattern

Introduction/Objective Uterine adenomatoid tumors are typically small, benign nodules. However, large cystic variants are exceptionally rare, creating diagnostic pitfalls. We report a 48-year-old female with a 15 cm uterine fundus mass, highlighting this uncommon presentation. Few documented cases exceeding 10 cm emphasize this rarity. Methods/Case Report A 48-year-old female presented with a palpable uterine fundus mass. CT revealed a 15 cm, well-defined, low-attenuation cystic mass, prompting surgical excision. Grossly, it was a multilocular cyst with serous fluid. Microscopically, the tumor exhibited organized cystic branching spaces in a background of benign smooth muscle cells. Scattered signet ring-like cells were identified; however, no substantial nuclear atypia or mitotic activity was observed. The tumor showed solid areas partially infiltrating the myometrium and cytoplasmic vacuoles. Immunohistochemistry demonstrated calretinin, WT1, pan CK positivity; CD31, SMA, CEA, inhibin negativity; and low Ki67. A definitive diagnosis of uterine cystic adenomatoid tumor was made, and the patient remained healthy during a seven-year follow-up. Results NA Conclusion Accurate histological and immunohistochemical evaluation is essential to differentiate rare cystic adenomatoid tumors from mimics (leiomyoma, hemangioma, lymphangioma, lipoleiomyoma, adenocarcinoma). This evaluation guides appropriate management, which typically involves simple surgical excision, offering a favorable prognosis and avoiding unnecessary radical interventions; however, rare cases may still require hysterectomy.