Anal canal neuroendocrine carcinoma with Pagetoid extension

Abstract

A case of anal canal neuroendocrine carcinoma with Pagetoid intraepithelial extension is presented. An 80-year-old man was admitted to hospital with a complaint of pain in the anorectal region. Clinical examination revealed a hard and fixed mass in the anal canal, and subsequent biopsy of the lesion showed it to be a carcinoma. The surgically resected specimen showed a solid tumor measuring 3.4 x 3.2 cm within the area from the surgical anal canal to the anatomical anal canal. Tumor cells proliferated predominantly with compact nests. Many tumor cells had a high nuclear-to-cytoplasmic ratio, dispersed chromatin, and conspicuous nucleoli. Additionally, neoplastic cells focally formed a glandular structure. Some polygonal neoplastic cells were small with round nuclei. A rosette-like arrangement was also focally observed. In addition, tumor cells exhibited Pagetoid extension into the overlying epithelium of the histological anal canal. Both the underlying original neoplastic cells and the Pagetoid spreading tumor cells showed cytoplasmic granules positive for Grimelius staining and immunopositivity for carcinoembryonic antigen, synaptophysin and cytokeratins 7 and 20. These findings are highly suggestive of neuroendocrine differentiation of adenocarcinoma cells. To the best of our knowledge, this is the first case of anal canal neuroendocrine carcinoma with Pagetoid extension into the overlying epithelium of the histological anal canal.

Anal canal neuroendocrine carcinoma associated with squamous intraepithelial neoplasia: A human papillomavirus 18‐related lesion

“…reviewed a series of gastrointestinal NECs and suggested that NECs arising in the squamous‐lined parts of the gastrointestinal tract, including the esophagus and anal canal, are mostly small‐cell type, whereas large‐cell type NECs are more prevalent in glandular mucosa‐lined areas 6 . In agreement with this study, the majority of previously reported anal canal NECs were small‐cell type 1,3 …”

“…Neuroendocrine carcinoma (NEC) of the anal canal is quite rare, and detailed analyses have been mostly available as isolated case reports 1–3 . Similar to NECs of other gastrointestinal tract organs, anal canal NEC is regarded as a highly aggressive tumor 1,2,4 .…”

“…This implies that at least some of the gastrointestinal NECs may not directly originate from neuroendocrine cells but may arise from preexisting tumors of more common types. Indeed, a case of anal canal NEC with adenocarcinoma component has been reported 3 …”

“…Neuroendocrine carcinoma (NEC) of the anal canal is quite rare, and detailed analyses have been mostly available as isolated case reports. [1][2][3] Similar to NECs of other gastrointestinal tract organs, anal canal NEC is regarded as a highly aggressive tumor. 1,2,4 In the World Health Organization classification, 4th edition, NECs are classified into small-cell and large-cell types.…”

“…6 In agreement with this study, the majority of previously reported anal canal NECs were smallcell type. 1,3 The histogenesis of anal canal NECs remains controversial. Since endocrine cells are present in rectal-type mucosa and the anal transitional zone mucosa of the anal canal, NECs have been suggested to be derived from these cells.…”