Ovarian Mucinous Tumor Presenting Atypical Lobular Endocervical Glandular Hyperplasia-Like Appearance in a Patient With Germline STK11 p.F354L Variant: A Case Report

Peutz-Jeghers syndrome (PJS) is associated with female genital lesions, such as cervical gastric-type adenocarcinoma and lobular endocervical glandular hyperplasia (LEGH). However, ovarian mucinous borderline tumors (OMBT) with atypical LEGH-like histology have not been described. The patient was a 60-year-old female with PJS clinically diagnosed at 23 years old with gastrointestinal polyposis. Abdominal distension was noted, and computed tomography scan revealed bilateral breast masses, multiple lung nodules, and a multicystic ovarian tumor. A needle biopsy revealed invasive ductal carcinoma of the breast. For the ovarian tumor, simple hysterectomy and bilateral salpingo-oophorectomy were performed. The left ovarian tumor was 25 × 20 × 12 cm in size and a multicystic tumor containing yellowish mucus without a solid part. Histologically, the cyst wall was covered with mucus cells with focal mild-to-moderate cellular atypia, forming LEGH-like architectures. The glandular cells were immunohistochemically positive for MUC5AC, MUC6 (focal), HIK1083 (focal), and HNF4α. Stromal invasion was not observed. Cervical lesions were not observed. The final pathological diagnosis was OMBT showing atypical LEGH morphology. Targeted sequencing of nontumor tissues revealed the germline STK11 p.F354L variant. Six months later, peritoneal dissemination of adenocarcinoma showing features similar to those of the ovarian tumor was observed, and the patient died of the disease. In summary, we report a case of OMBT with an atypical LEGH-like appearance in a patient with germline STK11 p.F354L variant. This case provides us with unresolved questions regarding the pathogenicity of this STK11 variant and the malignant potential of OMBT with this unusual morphology.