PMC4124645_01
(a) Contrast-enhanced computed tomography scan of the pelvis reveals a rectal mass involving the anterior, right lateral, and posterior walls of the rectum. (b) Computed tomography scan showing numerous hypodense masses throughout the liver consistent with liver metastases. (c) Contrast-enhanced computed tomography scan of the chest showing bilateral lung nodules and mediastinal lymphadenopathy secondary to metastatic disease. (d) Picture from sigmoidoscopy showing a fungating, ulcerated, and partially obstructing rectal mass, involving two-thirds of the luminal circumference.
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A computed tomography (CT) scan of the abdomen and pelvis revealed a rectal mass involving the anterior, right lateral, and posterior walls of the rectum beginning approximately 6 cm from the anal verge (Figure 1(a)). In addition, innumerable hypodense masses throughout the liver as well as retroperitoneal and pelvic lymphadenopathy were seen (Figure 1(b)). A subsequent CT chest showed numerous bilateral lung nodules and mediastinal lymphadenopathy (Figure 1(c)). Flexible sigmoidoscopy revealed a fungating, ulcerated and partially obstructing rectal mass, involving two-thirds of the luminal circumference, located 6 cm from the anal verge (Figure 1(d)).
((a) and (b)) Large cell neuroendocrine carcinoma infiltrating the connective tissue stroma of the colorectal biopsy, as nests of cells. There is associated tumor necrosis (arrows). Normal colonic mucosa is visible at the top of the field in (a). (c) The neoplastic cells reveal hyperchromatic nuclei with inconspicuous nucleoli, and a mitotic figure (arrow) is visible to the left, in the nest of neoplastic cells. ((d), (e), and (f)) On immunohistochemical staining the neoplastic cells stained positive for synaptophysin (diffuse cytoplasmic brown staining), chromogranin (focal cytoplasmic brown staining), and expressing a high Ki-67 labeling index of up to 50% cells (brown nuclear staining).
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On microscopic examination, nests of tumor cells infiltrated colonic stroma with associated tumor necrosis (Figure 2, A&B). The individual tumor cells exhibited moderate eosinophilic cytoplasm, hyperchromatic, pleomorphic nuclei and frequent mitotic figures (Figure 2(c)). Immunohistochemical study revealed cytoplasmic staining for neuroendocrine markers synaptophysin and chromogranin consistent with neuroendocrine differentiation (Figures 2(d) and 2(e)). Staining for proliferation marker Ki-67 revealed positive nuclear staining in up to 50% of cell nuclei consistent with a high proliferation rate in tumor cells (Figure 2(f)).