Colonic Large Cell Neuroendocrine Carcinoma with Extensive Carcinomatosis: A Highly Aggressive Tumor

Abstract

Abstract Introduction/Objective Large cell neuroendocrine carcinoma (LCNEC) of the colon is an exceedingly rare and aggressive neuroendocrine carcinoma. These tumors are associated with a poor prognosis, as they are commonly diagnosed in advanced stages with distant metastases. We present a case of a patient with colonic LCNEC with carcinomatosis peritonei who underwent surgical resection and hyperthermic intraperitoneal chemotherapy. Methods/Case Report The patient is a 49-year-old Caucasian male who presented with several months history of occasional hematochezia, constipation, 40-pound unintentional weight loss, and reflux. An initial diagnosis of adenocarcinoma of colorectal origin was rendered. Subsequently, the patient underwent a low-anterior resection with hyperthermic intraperitoneal chemotherapy (HIPEC). Histological evaluation of the rectosigmoid lesion demonstrated sheets of malignant epithelial cells with scant amphophilic cytoplasm, large pleomorphic vesicular nuclei, prominent nucleoli, and numerous mitotic figures. The tumor invaded the entire colonic wall and extended to the visceral peritoneum with extensive small vessel lymphovascular and perineural invasion with widespread involvement of the diaphragm, spleen, falciform ligament, and omentum. Immunohistochemical stains showed the tumor to be diffusely positive for CK20, CDX2, and synaptophysin; while negative for CK7, PAP, PSA, chromogranin, and p40. These findings are consistent with the diagnosis of a large cell neuroendocrine carcinoma. In addition, CD31 highlighted lymphatic spaces that were extensively filled with tumor cells. One-month post-operative, the patient remains in critical but stable condition with features of acute hypoxic respiratory failure and possible metastatic disease to the lung associated with pleural effusion. Results (if a Case Study enter NA) NA Conclusion Colonic large cell neuroendocrine carcinoma (LCNEC) is a rare, highly aggressive neuroendocrine carcinoma that frequently presents with distant metastases. Clinical awareness of the entity with early diagnosis and surgical resection remains the essential initial step. Utilizing immunohistochemistry stains to further characterize the tumor is critical to reach the correct diagnosis. Accumulating appropriate clinical data will aid in the establishment of future treatment protocols.