Small-cell neuroendocrine carcinoma of the rectum — a rare tumor type with poor prognosis: A case report and review of literature

Figure 1 Preoperative colonoscopy images. A: An ulcerated, bleeding lesion located in the upper rectum; B: Abundant necrotic tissue (orange arrow).

Figure 2 Preoperative contrast-enhanced computed tomography imaging scans. A: Computed tomography (CT) image showed the rectal lesion located in the upper rectum; B: CT image showed a lesion breaking through the adventitia.

Figure 3 Preoperative magnetic resonance imaging scans. A: Magnetic resonance imaging (MRI) showed a lesion breaking through the adventitia horizontally; B: MRI showed the lesion located in the upper rectum and the neoplasm breaking through the rectal adventitia (orange arrow).

Figure 4 Postoperative histopathological analysis. A: Hematoxylin-eosin stain (× 40) showing a morphology of mainly small cells with a thick chromatin layer, scarce cytoplasm and no obvious nucleoli; B: Immunopositivity for CD56 (× 40); C: Immunopositivity for neuron-specific enolase (× 40); D: Ki-67 (80%) was positive (× 40).

Figure 5 Contrast-enhanced computed tomography imaging scans 1 mo after surgery. A: Computed tomography imaging showed that there were multiple nodules in the lower abdomen, which was consistent with our physical examination; B: There were many new lesions in the pelvis (orange arrow) compared with Figure 2B.