## Most Common HPV Type in Cervical Cancer **Key Point:** HPV 16 is the most common cause of cervical cancer globally, accounting for approximately 50–55% of all cervical cancer cases. HPV 18 is the second most common, responsible for approximately 15–20% of cases. ### HPV Types and Cervical Cancer Risk | HPV Type | Prevalence in Cervical Cancer | Associated Lesions | Typical Progression | |----------|-------------------------------|-------------------|---------------------| | 16 | 50–55% | CIN 2/3, invasive cancer | Rapid malignant transformation | | 18 | 15–20% | Adenocarcinoma, CIN 1 | Can progress to adenocarcinoma | | 31 | 3–5% | CIN 2/3 | Moderate transformation risk | | 45 | 2–3% | Adenocarcinoma | Lower prevalence than 16/18 | **High-Yield:** HPV 16 and 18 together account for ~70% of all cervical cancers. HPV 16 is the most oncogenic type with the fastest progression from infection to malignancy. Persistent infection (>12 months) with high-risk HPV is the key driver of cervical carcinogenesis. **Clinical Pearl:** HPV 16 is associated with squamous cell carcinoma of the cervix, while HPV 18 has a predilection for adenocarcinoma and adenosquamous carcinoma. This distinction is clinically important for prognosis and treatment planning. ### Mechanism of Malignant Transformation HPV 16 encodes E6 and E7 oncoproteins that: 1. E6 protein inactivates p53 (tumor suppressor) 2. E7 protein inactivates Rb (retinoblastoma protein) 3. Loss of cell cycle checkpoints → uncontrolled proliferation 4. Integration into host genome → persistent infection → CIN → invasive cancer **Mnemonic:** **HPV 16 = "Sweet 16" = Most Common Cervical Cancer** (remember: 16 is the "sweet" spot for malignancy) **Warning:** Do not confuse HPV 6/11 (benign warts) with HPV 16/18 (cancer risk). The clinical context and histology help differentiate. [cite:Harrison 21e Ch 182]
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