This study aims to investigate the disease progression trends and risk factors of common AIDS-related tumors, including Kaposi sarcoma, lymphoma, lung cancer, and et al., among people living with HIV. By analyzing clinical data, the researchers hope to better understand how these cancers develop in HIV-infected patients and identify factors that may increase the risk. The findings may help improve early detection and treatment strategies for these cancers in the HIV population. This is an observational study, meaning participants will receive their usual medical care while researchers collect and analyze their health information. No experimental treatments will be given as part of this study.

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.

This study will enroll approximately 1 000 HIV-infected adults aged 18 years and older from 7 infectious disease treatment centers across China. Participants include individuals with confirmed AIDS who are receiving routine clinical care. The study employs an ambidirectional (retrospective-prospective) cohort design with a nested case-control analysis. The cohort comprises HIV-infected patients with and without AIDS-related malignancies (including Kaposi sarcoma, lymphoma, cervical cancer, anal cancer, oral cancer, colorectal cancer, and lung cancer). Within this cohort, cases are patients who developed malignancies during follow-up, and controls are matched HIV-infected patients without malignancies. The study population is intended to represent the broader demographic of adults living with HIV/AIDS under care in tertiary infectious disease centers in China.