Introduction: Synchronous squamous neoplasms of the anal canal and rectum are exceedingly rare and pose significant diagnostic and therapeutic challenges. The presence of squamous pathology in the anorectal region necessitates careful evaluation to distinguish between primary lesions, contiguous spread, and metastatic disease. Case Report: We report a case of human papillomavirus (HPV)-associated squamous cell carcinoma that initially presented as a rectal high-grade squamous intraepithelial lesion (HSIL). Magnetic resonance imaging demonstrated a locally advanced rectal mass with involvement of the mesorectal fascia and regional lymph nodes. Subsequent endoscopic ultrasound (EUS) confirmed the extent of rectal disease and additionally identified a previously unrecognized, spatially distinct lesion in the anal canal. Biopsy of the anal lesion revealed HSIL with diffuse p16 positivity, supporting HPV-associated pathology. Conclusion: This case highlights the diagnostic complexity of anorectal squamous lesions and underscores the importance of comprehensive evaluation of both the rectum and anal canal when squamous pathology is identified at either site. Early recognition of synchronous lesions is critical for accurate staging and optimal management.
Sehdev et al. (Thu,) studied this question.