Metachronous serous endometrial intraepithelial carcinoma and serous peritoneal carcinoma: analysis of probable independent lesions

BACKGROUND Uterine serous endometrial intraepithelial carcinoma (SEIC) is an immediate precursor of invasive carcinoma. The majority of stage IA SEICs are curable, but those with latent peritoneal metastasis and/or capillary lymphatics invasion may have poor prognoses Careful pathologic staging is thus needed to predict the risk of recurrence and to determine postoperative therapeutic strategies. CASE PRESENTATION A 71-year-old woman was hospitalized for the treatment of peritoneal carcinoma. She had undergone total hysterectomy and bilateral salpingo-oophorectomy due to SEIC (stage IA) at age 63 years, and had received medical check-ups every year since. Elevated serum CA125 (184 U/mL) was detected for the first time 8 years after surgery. A thorough workup revealed no potential primary lesion other than that in the peritoneum. Tumor reduction surgery was performed. Histologic analysis of the peritoneal lesion was high-grade serous carcinoma. The peritoneal carcinoma was diffusely immunostained for p53; thus, possible recurrence of SEIC was suspected. Tumor DNAs were microdissected from the uterine and peritoneal lesions and p53 mutation analysis was done. SEIC and peritoneal carcinomas had distinct p53 mutations that were mutually exclusive. CONCLUSIONS The present case raised a concern about the difficulty of histologic staging for SEICs. Although SEICs confined to the uterine endometrium in most cases predict a good prognosis, microscopic metastasis to the peritoneum may not be detectable at hysterectomy. If secondary malignancies of a serous phenotype develop years later, comprehensive reexamination of SEIC is mandated, with the help of DNA analysis.