A Rare Case of a Poorly Differentiated Neuroendocrine Rectal Tumor With Shared CLL Histology

Abstract

Introduction: Poorly differentiated neuroendocrine tumors (PDNETs) are rarely found in the GI tract1. Also uncommon is CLL infiltration of the GI tract. We report a rare case of a patient presenting with a rectal tumor that included both CLL and PDNET histology. Case Report: A 56 year old male with a history of CLL in remission presented with the complaint of 3 weeks of foul smelling diarrhea with blood spotting, bloating, and anorexia. The patient was taken for a colonoscopy, during which a 4cm friable, fungating mass was visualized on the right side of the distal rectum near the anal verge. A biopsy was performed which showed co-existing poorly differentiated neuroendocrine carcinoma and CLL. It was was strongly reactive for chromogranin and synaptophysin. It was also positive for CD5, CD20, and CD23. A CT scan revealed liver masses and extensive lymphadenopathy. Liver biopsy revealed PDNET histology. The patient was started on his first cycle of cisplatin and etoposide. Discussion: PDNETs comprise far less than 1% of GI malignancies. They are usually metastasized at discovery and may present similarly to adenocarcinomas. They are diagnosed by biopsy and histologic examination, demonstrating high mitotic rates and necrosis1. Untreated, survival is 6 months, in comparison to treatment with a regimen of etoposide and cisplatin, which offered an average survival of 15 months. In localized disease, adjuvant chemoradiation with surgery is recommended3. Management strategies for PDNETs rely on experience with small cell lung cancer therapies due to their rarity2. As for CLL, it is uncommon to see in GI tract biopsies unless it has converted to a diffuse large cell lymphoma. The prevalence of GI involvement in asymptomatic CLL patients based on autopsy studies is estimated at 7-13%3. On review of the literature, no case of co-existing CLL and PDNET was found. However, there are reports of increased rates of secondary malignancies in CLL patients, which may be related to immunological dysfunction or the effects of chemotherapy4.