Background: Using a 15-year experience in two teaching hospitals to illustr
ate the clinicopathologic, treatment and survival characteristics of cloaco
genic and squamous cell carcinoma of the anus. Method: A retrospective anal
ysis over a 15-year period from St Vincent's Hospital (SVH) and the Catholi
c Medical Center (CMC) in New York City. The patients in the study all had
a diagnosis of either squamous or cloacogenic cell carcinoma of the anus. R
esults: Cloacogenic and squamous cell carcinoma accounted for 2.5% of all,
large bowel cancers. In the population sample, 28/92 (30.4%) were of the cl
oacogenic type and 64/92 (69.6%) were of the squamous cell type. The male-t
o-female ratio was 1:1.5 in those with cloacogenic cancer and 1.8:1 in thos
e with squamous cell carcinoma. The mean age of presentation was 57 +/- 2.8
years for the squamous cell carcinoma patients and 66.3 +/- 3.4 years in t
hose with cloacogenic carcinoma (P < 0.02), 3/28 (10.7%) of patients with c
loacogenic cancer were human immune deficiency virus (HIV) positive while 1
5/64 (23.4%) of the squamous cell cancer patients were HIV positive. The mo
st common clinical presentation in both groups were rectal bleeding, pain,
constipation and the presence of an anal mass. Of patients with squamous ce
ll cancer 25% had evidence of infection with the human papilloma virus (HPV
) while none of those with cloacogenic cancer had evidence of HPV infection
(P < 0.0005). The treatment modality and survival were similar in both his
tologic groups. The most important factors that affect survival in both gro
ups are female sex and stage of disease. Conclusion: Cloacogenic and squamo
us cell carcinoma account for only a small proportion of large bowel cancer
s. The squamous cell type is the more common type and presents at a younger
age in both sexes. The squamous cell type is also more common in males and
is associated with human papilloma and HIV infection. Treatment modality a
nd survival is, however, similar in both histologic variants of anal cancer
.