Ultra-rapid peritoneal dissemination of a somatic STK11-mutant adnexal tumor: a case report with molecular correlation and literature review.

STK11-adnexal tumor (STK11-AT) is a recently characterized rare neoplasm tightly linked to Peutz-Jeghers syndrome (PJS) and marked by high recurrence potential. We report a 38-year-old woman who presented with a pelvic mass 9 months after resection of a primary left fallopian tube tumor. Initial pathology suggested a malignant Wolffian duct tumor, but expert pathological review and molecular profiling confirmed STK11-AT harboring a somatic STK11 nonsense mutation (c.367C>T, p.Gln123*), identified via next-generation sequencing (NGS) with a variant allele frequency (VAF) of 88.55%. Despite postoperative normalization of serum CA-125, surveillance imaging revealed ultra-rapid recurrence with extensive peritoneal carcinomatosis and retroperitoneal lymph node metastasis, necessitating comprehensive cytoreductive surgery. Recurrent lesions exhibited a high Ki-67 proliferation index (70%), consistent with aggressive biological behavior. This case expands the clinicopathological spectrum of STK11-AT by documenting hyperacute progression (shorter than the reported median recurrence interval of 17 months) and highlights the critical role of definitive molecular testing for diagnosis, as well as the need for intensive long-term surveillance even after R0 resection.