A Rare Case of Signet-ring Cell Carcinoma of Cecum with Endocrine Differentiation and Isolated Neuroendocrine Tumor 1 of Duodenum Presenting as Peritoneal Carcinomatosis

Abstract

Introduction: Colorectal cancer is the third leading cause of cancer related death in United States. Signet ring cell adenocarcinoma (SRCC) of colon is a very rare entity, accounting for less than 1% of cases. To date only 27 cases have been reported. We present an interesting case of signet cell carcinoma of cecum presenting as peritoneal carcinomatosis. Case: A 44-year-old male presented with diffuse left lower quadrant abdominal pain 2-3 years without weight loss, fever, chills and or night sweats. Initial CT abdomen and pelvis showed mural thickening of distal ileum and cecum, moderate ascites with infiltration of omentum, consistent with peritoneal carcinomatosis. Ascitic fluid cytology was negative for malignancy but showed reactive mesothelial cells. Colonoscopy revealed an exophytic mass in caecum (Figure 1) with biopsy positive for invasive adenocarcinoma, poorly differentiated with signet ring cells and endocrine differentiation (Figure 2). Upper endoscopy showed duodenal bulb polyp with pathology consistent with neuroendocrine type 1 tumor which appeared as an isolated finding. Patient had a repeat CT abdomen and pelvis for staging which showed further extensive lymphadenopathy involving the mediastinum, hilum and retroperitoneum. PET scan and peritoneal biopsy were requested by surgery and oncology after hospital discharge for further staging and management.Figure 1Figure 2Discussion: SRCC usually presents at an advanced stage with node positive disease and peritoneal dissemination, which results in poor prognosis. Pathologically the signet ring malignant cells are seen floating in abundant extracellular mucin pools. A unique feature of SRCC is its fibrotic appearance and preference for peritoneal metastasis over the liver. It is associated with a higher grade tumor burden associated with young age and distinct molecular patterns like microsatellite instability(MSI). In view of poor prognosis an adjuvant 5-FU-based therapy should be initiated to prevent recurrence of SRCC. The overall 5-year survival is 0-12%. There are no reports of SRCC with NET 1 in literature to date and this was likely an isolated rare finding. Conclusion: Primary SRCC is considered a distinct entity based on the clinical and pathological features. In this case report, we have shown a rare case of primary SRCC of the cecum with endocrine differentiation and neuroendocrine type 1 tumor of duodenum.