Aggressive Colorectal Signet Ring Cell Carcinoma Arising in Peutz-Jeghers Syndrome: A Rare Case of Missed Surveillance with Successful Multimodal Therapy.

Introduction: Peutz-Jeghers syndrome (PJS) is a rare hereditary condition characterised by mucocutaneous pigmentation and hamartomatous polyps in the gastrointestinal tract, associated with a significantly increased risk of malignancies, particularly gastrointestinal cancers. Among these, signet ring cell carcinoma (SRCC) of the colon is extremely rare and highly aggressive. Case description: We report a case of a 36-year-old Vietnamese male with a known history of PJS who presented with left iliac fossa pain. A colonoscopy revealed multiple colonic polyps and a type 3 ulcerated mass in the sigmoid colon; histopathology confirmed SRCC. The patient underwent a laparoscopic colectomy and was diagnosed with stage IIIC (T4aN2bM0) colonic SRCC. He completed twelve cycles of adjuvant FOLFOX4 chemotherapy. Fourteen months post-surgery, he remains disease-free with excellent performance status. Conclusion: This case illustrates the unpredictable progression of colonic SRCC in patients with PJS, emphasising the need for close periodic surveillance. Accurate diagnosis and timely interventions, including surgery and chemotherapy, are essential for improving outcomes in these high-risk individuals. LEARNING POINTS: People with Peutz-Jeghers syndrome (PJS) have a high risk of gastrointestinal cancers, including rare types such as signet ring cell carcinoma (SRCC).Early screenings and regular follow-up are crucial in PJS patients for the timely detection and management of cancerous and precancerous growths, to avoid severe progression.For colorectal SRCC in PJS patients, prompt surgery and chemotherapy could lead to positive outcomes.