A Rare Diagnosis of HPV-Positive Rectal Squamous Cell Carcinoma in a 59-Year-Old Heterosexual Woman: Implications for Screening Guidelines.

BACKGROUND Human papilloma virus (HPV)-16 and HPV-18 are the main high-risk types associated with anogenital cancers. Although the anus and rectum constitute reservoirs for persistent high-risk HPV infection, particularly in individuals with a history of receptive anal intercourse, clinical implications remain underrecognized. Current screening focuses on high-risk groups such as men who have sex with men, human immunodeficiency virus-positive individuals, and immunosuppressed populations; other at-risk groups, including heterosexual women with anal intercourse exposure, are largely underrecognized. CASE REPORT We encountered a rare case of HPV-positive rectal squamous cell carcinoma (SCC) in a 59-year-old heterosexual woman with no history of anal cancer, immunosuppression, or other established risk factors. The patient exhibited intermittent rectal bleeding and recent changes in bowel habits. Digital rectal examination revealed a firm, fixed mass approximately 3 to 4 cm from the anal verge. Colonoscopy demonstrated a partially circumferential, fungating, non-obstructing mass involving nearly one-third of the rectal lumen. Histopathological analysis confirmed invasive rectal SCC, with strong immunohistochemical staining for squamous markers. High-risk HPV subtypes 16, 18, and 33 were detected. Magnetic resonance imaging confirmed localized disease with muscularis propria invasion but no definite extension beyond the serosa or evidence of distant metastasis. The patient was referred to oncology for definitive management. CONCLUSIONS This case illustrates a rare but emerging diagnosis: HPV-positive rectal SCC in an immunocompetent woman without classic risk factors. It underscores the evolving spectrum of HPV-related malignancies and the need to reevaluate screening strategies to incorporate sexual behavior and HPV risk across all genders.