First Case of Ovarian Metastases From a Primary Retroperitoneal Mucinous Carcinoma Associated With Teratoma, With KRAS and ERBB3 Mutations: Case Report and Literature Review.

Primary retroperitoneal mucinous carcinomas (PRMCa) are exceedingly rare and poorly understood neoplasms, with <80 cases documented in the medical literature and molecular profiling hardly ever performed. Recent theories suggest that PRMCa might develop from mature cystic teratomas or Brenner tumors, mirroring their ovarian counterparts. However, only 2 cases of primary retroperitoneal mucinous tumors associated with teratoma have been reported in the literature to support this idea. In this paper, we detail an exceptional case: a 66-yr-old woman with ovarian metastases stemming from a PRMCa that originated in a mature cystic teratoma. The patient initially presented with a long-standing cystic mass in the retroperitoneum, diagnosed as a mucinous carcinoma after surgical removal. Following initial resection, the patient experienced rapid metastatic progression requiring aggressive treatment. Interestingly, the later ovarian metastases exhibited the full spectrum of architectural complexity observed in the initial lesion. This "maturation phenomenon," frequently observed in ovarian metastases of mucinous tumors, remains enigmatic. Molecular analysis revealed a KRAS mutation along with an ERBB3 mutation, making it the first instance of ERBB3 mutation being documented in this specific entity. This case underscores the importance of thorough data collection and continued research to improve our understanding of these rare tumors.