Disease Evolution and Risk Factors of AIDS-related Prevalent Cancers

Inclusion Criteria: 1. Age ≥ 18 years at the time of HIV diagnosis or study enrollment. 2. Confirmed diagnosis of HIV-1 infection documented by positive serological testing (HIV antibody screening with confirmatory Western blot or HIV-1 RNA PCR). 3. Confirmed HIV-1 infection based on established clinical and/or immunological criteria (e.g., CD4+ T-cell count \< 200 cells/μL, or presence of AIDS-defining conditions). 4. For the cohort phase: Received continuous or intermittent care at one of the participating centers with available baseline clinical data (CD4 count, HIV viral load, ART history) and at least 6 months of follow-up data. 5. For the nested case-control analysis - Cases: Pathologically or clinically diagnosed with an AIDS-related malignancy during the study period, specifically one of the following: Kaposi sarcoma, lymphoma, cervical cancer, anal cancer, oral cancer, colorectal cancer, and lung cancer. 6. For the nested case-control analysis - Controls: HIV-infected patients without a history of AIDS-related malignancy at the time of matching, selected from the same cohort using incidence density sampling. 7. Able and willing to provide written informed consent for prospective data collection, medical record review, and follow-up (applicable to the prospective component). Exclusion Criteria: 1. Concurrent malignancy other than the study-specified AIDS-related malignancy (for cases); or presence of any AIDS-related malignancy (for controls). 2. Systemic high-dose corticosteroid therapy (equivalent to prednisone ≥ 20 mg/day for ≥ 2 weeks) within 6 months prior to the index date. 3. Severe comorbid systemic disease or major organ dysfunction (e.g., decompensated cirrhosis, New York Heart Association Class III-IV heart failure, severe chronic kidney disease with eGFR \< 30 mL/min) that would independently limit survival or preclude study participation. 4. Inability or unwillingness to comply with study procedures, including clinical data collection, biological specimen collection, and follow-up assessments. 5. Pregnancy at the time of enrollment (for the prospective component only). 6. Any other condition that, in the judgment of the investigator, would compromise the subject's ability to participate in the study or interfere with the interpretation of study results.