A rare incidence of signet ring cell carcinoma of the rectosigmoid junction: a case report

Introduction and importance: Signet ring cell carcinoma (SRCC) is a rare type of adenocarcinoma. SRCC comprises 1.0% of all colon cancer and 0.7% of all rectal cancer. The SRCC spreads both hematologically and through lymph nodes making it highly invasive. The pathophysiology of the colorectal SRCC involves an alteration in the function of the RNF43, CDH-1, and SMAD4 genes as well as TGF-B signaling pathways, which are responsible for epithelial-mesenchymal transitions and stem cell properties. This also shows a higher rate of BRAF mutation, microsatellite instability-high (MSI-H) and CpG island methylator phenotype positivity Case presentation: A 17-year-old female patient with no known comorbidities presented with copious, bright red colored per rectal bleeding along with painful defecation. Colonoscopy revealed an eccentric growth that led to luminal narrowing. Multiple biopsies confirmed a 4 cm × 6 cm neoplastic lesion with locoregional lymphadenopathy, but no metastasis. The patient underwent anterior resection of the rectum, colostomy, and rectal stump closure. The sigmoid colon was resected up to the middle up to the third mesorectum followed by multiple re-explorations. Discussion: SRCC presents at an advanced stage with a poor prognosis because signet ring cells infiltrate the mucosa without forming a significant mass, hindering early diagnosis of this carcinoma. Among the previously published large-scale studies, SRCC involves the proximal colon, i.e., the cecum, ascending, and transverse colon. However, our case presents a less common left-sided presentation in a less-commonly presented demographic, a 17-year-old girl. The patient’s non-specific symptoms contributed to a delayed diagnosis. Despite this, the absence of metastasis in our late-diagnosed case is atypical of SRCC. Conclusion: SRCC should be considered as a differential diagnosis for young adults presenting with per-rectal bleeding and other common symptoms often seen in frequently diagnosed conditions. Therefore, early diagnosis along with appropriate surgical intervention combined with supportive treatment are important for better patient outcomes.