Neuroendocrine Dysplasia Combined in a Tubular Adenoma of Rectum: A Case Report
A 56-year-old female had a chief complaint of frequent loose stools and visited the local clinic in September 2012. The patient did not have any prior gastrointestinal problems. She had a previous surgical history for stress urinary incontinence in 2006, and had received re-operation for small bowel perforation that occurred in the sling operation. She was referred to the Kunkuk University Medical Center, Seoul, Korea for further evaluation. A colonoscopic examination was performed and revealed a large, laterally spreading circumferential mass at the rectum. The mass was greater than 5 cm in size. Due to the clinical suspicion of malignancy, a low anterior resection with extensive lymph node dissection was performed.\nUpon gross examination, a well-circumscribed, slightly elevated circumferential mass was identified in the rectum, measuring 6.0×5.0 cm (). Grossly, the mass was extending to the submucosa, exhibiting a fibrotic appearance with blurring of the muscularis mucosae. The lesion was entirely embedded and fully evaluated.\nHistologically, the elevated lesion was a typical tubular adenoma with low grade dysplasia, showing nuclear stratification and elongation (). Beneath the adenomatous polyp, multiple small cellular nests were observed at the base of the adenomatous polyp (). The cellular nests were clustered forming micronodules, and some of them fused together. At higher magnification, the cellular nests were composed of monotonous cells with eosinophilic, finely granular cytoplasm and stippled chromatin with central nuclei, reminiscent of neuroendocrine cells (). Prominent nucleoli or mitosis were absent or inconspicuous. These cell nests were infiltrating the lamina propria and muscularis mucosae, and some of the cell nests seemed to intermingle with the adenomatous polyp. A desmoplastic reaction was not observed. The endocrine cell clusters were scattered multifocally along the polyp, measuring 3 cm in total diameter. The largest individual neuroendocrine cell nest measured up to 220 µm in its greatest dimension. Twenty-three regional lymph nodes were dissected, but metastatic tumor cells were not identified.\nFor confirmative diagnosis, immunohistochemical staining of the chromogranin, synaptophysin, p53, and Ki-67 labeling index were performed. The cells were diffuse, strongly positive in chromogranin (), and weakly positive in synaptophysin. The chromogranin staining was not only positive in the neuroendocrine cell nests, but also focally positive in the basal cells of the adenomatous polyp. The p53 staining and Ki-67 labeling index were both negative in the neuroendocrine cell nests (). The patient recovered well without any complications, and follow-up colonoscopic examination 3 months after surgery found no evidence of recurrence.