Anal Squamous Cell Carcinoma (SCC)
The most likely diagnosis is D. Anal SCC, given the presence of HPV on biopsy and a palpable mass in the anal canal. 1
Rationale Based on HPV Association
HPV is the causative agent in 80-85% of anal squamous cell carcinomas, making this the strongest association among the answer choices. 1, 2 Specifically, HPV types 16 and 18 are most commonly implicated in anal SCC and its precursor lesion, anal intraepithelial neoplasia (AIN). 1, 2
- HPV is detected in approximately 90% of anal squamous cell cancers, making it second only to cervical cancer in the closeness of its association with this virus. 2
- The European Society for Medical Oncology (ESMO) guidelines explicitly state that squamous cell carcinoma of the anus (SCCA) and AIN are mostly attributable to HPV infection. 1
Clinical Presentation Consistent with Anal SCC
SCCA commonly presents with a mass, which aligns with this patient's abdominal/anal mass. 1
- According to ESMO guidelines, SCCA may present with any combination of a mass, non-healing ulcer, pain, bleeding, itching, discharge, fecal incontinence, and fistulae. 1
- The diagnosis of anal cancer is made by biopsy-proven histology, which has been performed in this case showing HPV. 1
Why Other Options Are Less Likely
Paget's disease (Option A) is not primarily HPV-associated and typically presents as an eczematous lesion rather than a mass with HPV positivity. 1
Bowen disease (Option B) represents squamous cell carcinoma in situ of the skin, but when HPV-positive lesions occur in the anal canal with a mass, they are classified as invasive squamous cell carcinoma rather than Bowen disease. 1
Adenocarcinoma (Option C) is specifically listed in ESMO guidelines as among the differential diagnoses that must be distinguished from squamous cell carcinomas through histological confirmation. 1 Adenocarcinomas of the anal canal are not typically HPV-associated and would show glandular rather than squamous differentiation on biopsy. 1
Diagnostic Confirmation
Histological confirmation is mandatory according to ESMO guidelines, as histopathological entities other than SCCs include adenocarcinoma, melanoma, gastrointestinal stromal tumors, poorly differentiated neuroendocrine tumors, and lymphoma. 1
- P16/HPV assessment is recommended in the diagnostic work-up of SCCA. 1
- The presence of HPV on biopsy strongly supports the diagnosis of squamous cell carcinoma over other histologic types. 1, 2
Common Pitfall to Avoid
Do not dismiss anal bleeding or masses as hemorrhoids, as diagnosis of SCCA is often delayed because bleeding is attributed to hemorrhoids. 1, 2 Digital anorectal examination is an essential low-cost clinical tool for detection of lesions in the anal area and should be performed in all patients with anal symptoms. 1