Expect the unexpected: cervical gastric-type adenocarcinoma in situ in a patient with long-standing Peutz-Jeghers syndrome — a case report and literature review

Background Peutz-Jeghers syndrome (PJS) is an autosomal dominant disorder caused by germline mutations in the STK11 tumor suppressor gene, associated with a significantly elevated lifetime risk of various malignancies. Gastric-type endocervical adenocarcinoma (G-EAC) and its precursor lesions represent one of the most challenging gynecologic manifestations due to their “deceptively bland” appearance, HPV-independent nature, and propensity to evade routine screening, often leading to delayed diagnosis and poor prognosis. Case presentation We report a 37-year-old woman with a 30-year history of PJS, presenting with persistent watery vaginal discharge for one year. Despite negative cervical cytology, negative HPV testing, normal colposcopic findings, and inconclusive imaging, her request for hysterectomy was initially declined due to absence of definitive malignant features. The patient subsequently sought care at a tertiary referral center in Shanghai, where post-hysterectomy pathological examination unexpectedly confirmed cervical gastric-type adenocarcinoma in situ (GAS-AIS). Conclusion This case highlights a critical message: a PJS patient with persistent watery vaginal discharge may harbor gastric-type cervical glandular neoplasia despite negative cytology, negative HPV testing, apparently normal cervical examination, and inconclusive imaging. Persistent watery discharge in this specific population should be considered a “red flag” for gastric-type lesions, which may arise from lobular endocervical glandular hyperplasia (LEGH). For PJS patients with persistent unexplained vaginal discharge, we suggest that clinical suspicion — rather than cytology or colposcopy findings — should be the primary trigger for diagnostic excisional procedures. We present a comprehensive literature review of PJS-associated G-EAC and advocate for updated surveillance protocols, including random cervical biopsies or excisional procedures in symptomatic PJS patients, regardless of colposcopic findings.