Molecular analysis of appendiceal mucinous cystadenoma and rectal adenocarcinoma in a patient with urothelial carcinoma: a case report.

Introduction: In this report, we present the case of a patient affected by appendiceal cystadenoma, a colorectal adenocarcinoma, and a concomitant bladder carcinoma, as well as the results of the molecular study of the most relevant mutational pathways involved in these tumors.

Case Presentation: A 68-year-old Italian man was admitted to our unit complaining of macrohematuria, rectorrhagia, and rectal tenesmus for about 2 months. A colonoscopy showed the presence of a rectal lesion at 11cm from the anal margin; multiple biopsies were performed and a diagnosis of moderately differentiated adenocarcinoma was made. Abdominal ultrasonography and total body computed tomography performed subsequently to stage the rectal cancer showed the presence of two round nodules, interpreted as swollen lymph nodes of neoplastic origin, at the anterior aspect of the iliopsoas muscle and a budding lesion affecting the bladder. The patient underwent transurethral biopsy of the lesion in the right retrotrigonal region; the diagnosis was grade II urothelial carcinoma. The patient underwent an open anterior rectal resection with loco-regional lymphadenectomy. An enlarged appendix and a voluminous whitish soft-tissue lesion requiring an appendicectomy were detected perioperatively. Transurethral resection of the bladder lesion was also performed. The histological examination revealed that the nodular lesions in the appendix were due to a cystadenoma. For mutation analysis, genomic deoxyribonucleic acid was isolated from tumor tissue samples; for PIK3CA mutations, screening revealed that all three samples analyzed carried mutations in exon 9.

Conclusions: Appendiceal mucoceles are rare but require adequate surgical treatment, given their malignant potential and the possibility of causing peritoneal pseudomyxoma. It is essential to make a correct preoperative evaluation based on a colonoscopy rather than ultrasound and computed tomography to exclude synchronous neoplasias often associated with mucoceles and to plan the optimum surgical strategy. The association between appendiceal mucoceles and other neoplasias is relatively frequent, especially with colorectal cancer. Oncogenic activation in the PIK3CA-depending pathway may contribute substantially to the pathogenesis of the different solid tumors in the same patient.