Synchronous occurrence of advanced neuroendocrine carcinoma and tubular adenocarcinoma of the rectum

Abstract

This report presents a rare case with the synchronous occurrence of advanced neuroendocrine carcinoma (NEC) and tubular adenocarcinoma of the rectum. A 52-year-old Japanese male presented with general fatigue and bloody stool. Endoscopic examination showed an ulcerated lesion of the lower rectum. The pathological diagnosis of biopsy specimens from this lesion indicated moderately differentiated adenocarcinoma. He was referred to the surgical outpatient clinic with advanced rectal cancer. Barium enema indicated two lesions in the upper and lower rectum. Computed tomography revealed multiple hepatic metastases. A low anterior resection was performed with lymph node dissection. The resected specimen indicated an elevated lesion with ulceration in the upper rectum and an ulcerated lesion in the lower rectum. Histopathological and immunohistochemical analyses revealed NEC from the upper rectum and moderately differentiated tubular adenocarcinoma from the lower rectum. These two lesions were completely separated from each other. Therefore, this case demonstrates the synchronous occurrence of advanced NEC and tubular adenocarcinoma in the rectum.

Keywords: Neuroendocrine carcinoma; Rectum; Small cell type; Synchronous occurrence; Tubular adenocarcinoma.

Fig. 1

Barium enema revealed two lesions in the upper rectum (a). One was an elevated lesion on the oral side (arrows) and the other was an ulcerated lesion on the anal side of the upper rectum (arrowheads). Computed tomography revealed a rectal mass (b) and multiple hepatic metastases (c).

Fig. 2

The surgical specimen revealed an elevated lesion with ulceration on the oral side of the upper rectum (arrows) and an ulcerated lesion on the anal side of the upper rectum (arrowheads).

Fig. 3

Histopathological examination with hematoxylin and eosin staining revealed NEC in the oral lesion from the upper rectum (a, ×200) and moderately differentiated tubular adenocarcinoma from the anal lesion on the upper rectum (b, ×200). Immunohistochemical analyses indicated that many NEC cells were positive for synaptophysin (c, ×200) and chromogranin A (d, ×200).