Context: A large percentage of cases of perianal Paget disease are associated with an internal cancer, most commonly rectal adenocarcinoma. Immunostains for cytokeratin 7, cytokeratin 20, and gross cystic disease fluid protein 15 are useful in identifying cases associated with rectal adenocarcinoma. The Paget cells and rectal adenocarcinoma cells of these lesions typically have a cytokeratin 7(+)/cytokeratin 20(+)/gross cystic disease fluid protein 15(-) immunophenotype. It is not known whether rectal adenocarcinoma unassociated with perianal Paget disease has the same cytokeratin profile as rectal adenocarcinoma associated with perianal Paget disease.
Objective: To evaluate the immunohistochemical cytokeratin 7 and 20 profile of resected rectal adenocarcinoma unassociated with perianal Paget disease as well as that of normal anal glands from hemorrhoidectomy specimens.
Design: We performed immunohistochemistry for cytokeratins 7 and 20 on tissues from 30 cases of rectal adenocarcinoma unassociated with perianal Paget disease and 12 hemorrhoidectomy specimens from 12 cases with normal anal glands. We defined positive staining as any immunoreactivity within the neoplastic cells.
Results: Twenty-six of 30 cases of rectal adenocarcinoma (87%) had a cytokeratin 7(-)/cytokeratin 20(+) immunophenotype, similar to the immunophenotype of cases of nonrectal large intestine adenocarcinoma. In 4 cases (13%), neoplastic cells coexpressed cytokeratins 7 and 20. Anal glands stained strongly for cytokeratin 7 but were negative for cytokeratin 20 in all cases, and the anal transitional zone mucosa had a similar immunophenotype.
Conclusions: Rectal adenocarcinoma unassociated with perianal Paget disease has a cytokeratin profile similar to that of nonrectal large intestine adenocarcinoma. These data suggest that rectal adenocarcinoma unassociated with perianal Paget disease has a different cytokeratin profile than rectal adenocarcinoma associated with perianal Paget disease.