Goblet cell adenocarcinoma of the anal canal with perianal Paget disease: A rare case report with literature review

Introduction: AS an uncommon neoplasm, goblet cell adenocarcinoma (GCA) is characterized by mixed endocrine-exocrine features. It is almost exclusively found in the appendix. Primary GCA of the anal canal is extremely rare.

Case presentation: Herein we describe a novel rare case of 74-year-old Chinese female who is diagnosed with GCA in the anal canal with perianal Paget disease, including a brief review of the literature. In the lesion of anal canal, the tumor was composed of signet-ring-like cells on confluent growth model and copious mucin was produced as well. Simultaneously, the results of immunohistochemistry showed signet-ring-like cells were positive for CK20, CDX2, synaptophysin (Syn), CD56, carcinoembryonic antigen (CEA) and Villin. Meanwhile, the Ki67-labeling index reached 40%. In the lesion of perianal Paget disease, the small groups of atypical neoplastic cells were present in the epidermis. Immunohistochemically, the neoplastic cells were positive for CK20, CDX2 and epithelial membrane antigen, but negative for CK7, GCDFP15, S100, HMB45, and P63. The Ki67-labeling index reached 60% in the most concentrated spot.

Conclusions: Extra-appendiceal GCA was rare and easily under-recognizable. The diagnosis of GCA was seldom made preoperatively. Occasionally, GCA could occur in the anal canal accompanied by perianal Paget disease. So careful rectal examination was important in the patient with perianal Paget disease for avoid missing diagnosis of GCA on anal canal. GCA may show aggressive clinical behavior compared with typical well-differentiated neuroendocrine tumors. Therefore, we should pay more attention on the recognization of this rare disease.