A case of intraepithelial carcinoma of the fallopian tube diagnosed due to the presence of pleural effusion and metastasis in a patient with inguinal hernia

Usually, fallopian tube carcinoma is associated with peritoneal dissemination and cancerous ascites. We report the case of a patient with an inguinal hernia and intraepithelial fallopian tube cancer who presented with pleural effusion and cystic metastasis. A 76-years-old woman, G1P1, was referred to our hospital for further investigation and treatment of her pleural effusion. She underwent a hysterectomy for uterine fibroids at the age of 49. Contrast-enhanced computed tomography revealed a right-sided pleural effusion and a cyst in the right femoral inguinal hernia. Pleural fluid cytology revealed the presence of malignant cells. The pathological diagnosis from the pleural biopsy specimen was a serous adenocarcinoma. Pelvic magnetic resonance imaging revealed a diffuse-weighted high signal and contrast-enhancing mural nodule in the right femoral inguinal hernia. Inguinal hernia cystectomy and bilateral adnexectomy were performed under the suspicion of peritoneal carcinoma. The postoperative pathological diagnosis was high-grade serous carcinoma （HGSC） in the peritoneal node and serous tubal intraepithelial carcinoma in the right fallopian tube. Since both conditions have similar immunostaining images, she was diagnosed with stage ⅣA fallopian tube cancer. Approximately 50％ of peritoneal serous carcinomas derived from epithelial carcinoma originate from the fallopian tube. The criteria for determining the primary site of HGSCs have recently been proposed. The diagnosis of a primary peritoneal carcinoma is made after excluding the fallopian tubes and ovaries as the primary sites of carcinogenesis. In this case, the preoperative examination revealed only peritoneal lesions, leading to the suspicion of peritoneal carcinoma. However, because the postoperative pathological examination revealed microscopic lesions in the fallopian tubes, her final diagnosis was intraepithelial fallopian tube carcinoma.