Abstract
A 68 year old male with a history of Crohns disease treated with immunotherapy presented for evaluation of presumed anal fissuring. On endoscopy, the patient was found to have a mass in the anal canal that was not identified on the patients most recent colonoscopy one year prior. Biopsy showed small cell carcinoma (SmCC) with an extensive background of low-grade squamous intraepithelial neoplasia (LSIL). In situ hybridization for high-risk and low-risk human papillomavirus (HPV) serotypes demonstrated the presence of high-risk HPV in the SmCC, while low-risk HPV was present in the LSIL, and both high- and low-risk HPV were present in the HSIL. Anal canal neoplasms account for less than 5% of gastrointestinal tract malignancies, and SmCC is a vanishingly rare tumor within this category. There is a known association of human papillomavirus infection with SmCC and squamous lesions of the anal canal and other anatomic locations, including the cervix. To the authors knowledge, there have been no prior reports of high-risk HPV positive SmCC arising adjacent to a low-risk HPV positive squamous intraepithelial lesion. In fact, most literature in this regard describes patients with multiple morphologically distinct tumor types infected with a single HPV serotype. However, co-infection with multiple HPV serotypes has been reported in premalignant lesions, particularly in patients with human immunodeficiency virus (HIV). Therefore, this case raises two important points for consideration. First, adequate sampling in premalignant lesions should be performed to evaluate for a higher-risk or more aggressive lesion, especially in the setting of an immunocompromised state. Second, infection with one HPV serotype is not mutually exclusive of infection with other HPV serotypes, even in lesions that seemingly appear related.
Financial Disclosure:
No current or relevant financial relationships exist.
