Comment:
The rectum is the site of extensive replacement by squamous
epithelium showing varying degrees of dysplasia as well as
intraepithelial and focal superficial invasion by squamous cell
carcinoma. The tumor has a basaloid growth pattern consistent
with cloacogenic carcinoma derived from the transitional mucosa
at the junction between the rectum and anus. The colonic mucosa shows mainly quiescent
changes consistent with longstanding inflammatory bowel disease
however focal ulceration and acute inflammation is present. Of
note is the presence in the rectum for fissure formation which
favors long standing Crohn's disease. There may have been underlying Crohn's disease
which produced anorectal fissures which overtime led to healing
with squamous metaplasia. Subsequently this transitional
epithelium underwent malignant change to a cloacogenic form of
squamous cell carcinoma.
Contributed by Jeff Nine, M.D. and Lina Perry, M.D.
