[654] Intrarectal Patch of Primary Squamous Cell Carcinoma (SCC): A Rare HPV-Related Variant

Richa Jain, Ihab Lamzabi, Shriram Jakate. Rush University Medical Center, Chicago, IL

Background: Unlike adenocarcinoma, primary rectal SCC is extremely rare and largely presumed to be proximal extension of anal SCC. In the absence of anal SCC, an isolated intrarectal SCC is clinically and endoscopically unforeseen and poses challenges regarding its origin, pathogenesis, extent, behavior and management. We describe 6 cases of primary intrarectal SCC including possible pathogenetic pathway, distinctive patch-like endoscopic findings, management and follow-up.
Design: We recovered 6 cases of isolated rectal SCC (ages 41-94, median age 60) from our database between 2005-2012. Other cases with current or past anal or cervical condyloma, dysplasia or SCC were excluded. The clinical presentation, endoscopic findings, pathological features including HPV (in-situ hybridization for HPV6 and 16) and p16 immunostain, management and follow-up of these cases were reviewed.
Results: Males outnumbered females in our small population (2:1). Clinical presentation included rectal bleeding (2/6), screening colonoscopy (2/6), IBD surveillance (1/6) and colonoscopy after detection of liver metastasis (1/6). Endoscopically, no perianal or anal canal abnormality was seen, all tumors were above the dentate line (range of 1-6cm),surrounded on all sides by normal rectal mucosa and described either as irregular pale firm patch (4/6) or nodular carpet-like lesions (2/6). Histologically, 4/6 showed invasive moderately or poorly differentiated SCC and 2/6 SCC-in-situ (CIS). No squamous metaplasia was seen in the surrounding rectal mucosa. All 6 tumors (100%) were strongly and diffusely positive for p16 and 4/6 cases (66%) were positive for HPV 16 (high risk HPV). 2 patients with CIS underwent endoscopic mucosal resection (EMR), and 4 patients with invasive SCC underwent chemoradiotherapy (Nigro protocol). Patients with CIS remained disease-free, one patient with initial liver metastasis died and 1 of remaining 3 patients underwent subsequent APR (range of follow-up 6 months to 6 years).
Conclusions: Primary intrarectal SCC, unaccompanied by anal SCC is extremely rare and may be symptomatic or detected incidentally. Endoscopically, it is distinctly patch-like in most cases. While HPV is known to infect anal and cervical squamous epithelium, occasionally an isolated patch of distal rectal mucosa is infected by high risk HPV. Even when HPV cannot be demonstrated, the oncogenetic pathway appears to finally involve the cyclin-dependant kinase inhibitor 2A (P16). Even with uncertainty regarding its management, most patients are successfully treated by EMR for CIS and chemoradiotherapy for invasive SCC similar to anal SCC.
Category: Gastrointestinal

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 100, Wednesday Morning


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