Metastatic prostate cancer mimicking colorectal cancer: a rare case of peritoneal and mesocolic lymph node involvement

Metastatic prostate cancer seldom involves the gastrointestinal tract, with simultaneous peritoneal and mesocolic nodal spread and is unreported in literature. We describe the case of a 93-year-old man with stable metastatic prostate cancer who presented with sigmoid obstruction secondary to sigmoid adenocarcinoma. Pathological assessment of the specimen confirmed sigmoid adenocarcinoma as well as prostate cancer deposits in colonic serosa, peritoneum, and mesocolic nodes that was not evident on preoperative imaging. This case highlights a previously undocumented metastatic pattern, the limitations of conventional imaging, and the importance of intra-operative vigilance in dual malignancies.