A 38-year-old woman undergoes cervical screening and is found to have cervical intraepithelial neoplasia (CIN). Which HPV type is the most common causative agent in cervical carcinoma and its precursor lesions?

Explanation

## HPV Types and Cervical Carcinoma Risk **Key Point:** HPV 16 is responsible for approximately 50–55% of all cervical cancers and is the single most common causative agent globally. ### HPV Classification by Risk | HPV Type | Risk Category | Prevalence in Cervical Cancer | Clinical Significance | |----------|---------------|-------------------------------|----------------------| | HPV 16 | High-risk (HR) | 50–55% | Most oncogenic; associated with SCC | | HPV 18 | High-risk (HR) | 15–20% | Second most common; associated with adenocarcinoma | | HPV 31 | High-risk (HR) | 3–5% | Less common; still oncogenic | | HPV 33 | High-risk (HR) | 3–5% | Less common; still oncogenic | **High-Yield:** HPV 16 and HPV 18 together account for ~70% of cervical cancers. HPV 16 alone is the leading cause in both developed and developing countries, including India. ### Mechanism of Oncogenesis 1. HPV 16 and 18 encode viral oncoproteins E6 and E7 2. E6 protein inactivates p53 (tumour suppressor) 3. E7 protein inactivates Rb (retinoblastoma protein) 4. Loss of cell cycle checkpoints → malignant transformation **Clinical Pearl:** HPV 16-positive CIN lesions have a higher risk of progression to invasive carcinoma compared to other HPV types, making it the most clinically significant. **Mnemonic:** **HR-HPV-16-FIRST** — High-Risk HPV 16 is the First and most frequent cause of cervical cancer. [cite:Robbins 10e Ch 22]