Infrequent HPV Infection in Colorectal Neuroendocrine Carcinoma: Molecular and Histologic Characteristics

Area of Science:

• Oncology
• Gastroenterology
• Pathology

Background:

• Colorectal neuroendocrine carcinomas (NECs) are rare, aggressive tumors with unclear characteristics and treatment strategies.
• Anorectal NECs may be linked to high-risk human papillomavirus (HPV), indicating varied origins.
• Understanding NEC heterogeneity is crucial for effective management.

Purpose of the Study:

• To analyze clinicopathologic, molecular, and outcome data of colorectal NECs.
• To investigate the role of HPV in colorectal NEC pathogenesis and prognosis.
• To compare treatment responses in different NEC subtypes.

Main Methods:

• Retrospective review of 12 colorectal NEC cases.
• Histologic, immunohistochemical, and molecular profiling (including mutation analysis and HPV testing).
• Clinical outcome assessment and survival analysis.

Main Results:

• Seven small cell NECs and five large cell NECs were identified; most originated in the rectum.
• Common mutations included TP53 (75%), KRAS, RB1, FBXW7, and BRAF. One case had MMR deficiency.
• A single HPV-positive rectal NEC lacked common mutations and had a favorable long-term outcome (54 months). Platinum-based chemotherapy improved survival in small cell NECs compared to FOLFOX (13.5 vs. 4 months).

Conclusions:

• Colorectal NECs exhibit significant histologic and molecular heterogeneity.
• Small cell NECs may benefit more from platinum-based chemotherapy.
• HPV-associated NECs could represent a distinct subset with a better prognosis, but p16 is not a reliable marker for HPV status.