Background: Synchronous colorectal carcinoma (SCRC), defined as two or more distinct primary colorectal malignancies diagnosed simultaneously or within six months is rare in patients with colorectal cancer. The coexistence of multiple synchronous tumors with signet ring cell differentiation is exceedingly rare and presents significant diagnostic and therapeutic challenges because of its aggressive biology and poor prognosis.
Case Presentation: A 75-year-old woman with remote breast cancer, a previously identified tubulovillous adenoma lost to surveillance, and other comorbidities presented with isolated right upper quadrant abdominal (RUQ) pain and nausea. Labs and imaging of the abdomen and pelvis were unremarkable. Esophagogastroduodenoscopy (EGD) was normal. Colonoscopy identified three benign polyps and three separate malignant-appearing colonic masses involving the distal transverse colon, hepatic flexure, and transverse colon. Histopathology revealed poorly differentiated invasive adenocarcinoma with prominent signet ring cell features in two lesions, while the third demonstrated a distinctly different morphology consistent with a separate synchronous primary colorectal carcinoma.
Conclusion: This case underscores that isolated abdominal pain with nondiagnostic imaging does not exclude colorectal malignancy, particularly in patients with previously identified advanced adenomas who have been lost to surveillance. Complete colonoscopic evaluation remains essential for detecting synchronous colorectal cancers, establishing the diagnosis, and guiding definitive multidisciplinary management.