A Dangerous Partnership: Malignancy and Antiphospholipid Antibodies

Antiphospholipid syndrome (APS) is characterized by persistent antiphospholipid antibodies (aPL) associated with thrombotic and/or obstetric complications. Malignancies are strongly prothrombotic, and growing evidence suggests clinically relevant interactions between aPL and cancer. Interpretation remains challenging because many oncologic studies rely on non-criteria aPL profiles, low titers, or single-time measurements that may not reflect clinically meaningful APS. The aim was to summarize current evidence regarding aPL in malignancy, focusing on prevalence, laboratory profiles, thrombotic manifestations, catastrophic antiphospholipid syndrome (CAPS), paraneoplastic associations, and potential clinical implications in oncology patients. A focused narrative review was conducted using PubMed/MEDLINE and PubMed Central (through October 26, 2025). Predefined search strategies emphasized antibody profile, persistence (≥12 weeks when available), tumor type, and thrombotic outcomes. Studies were selected for clinical relevance and verifiability, with structured synthesis of key findings. Meta-analytic data demonstrate increased anticardiolipin positivity in gastrointestinal, genitourinary, and lung cancers, whereas lupus anticoagulant and anti-β2GPI findings remain heterogeneous. Antiphospholipid antibodies positivity was frequently transient or low titer, limiting clinical interpretation. Persistent or high-risk aPL profiles were associated with increased thrombosis in selected subgroups. Catastrophic antiphospholipid syndrome and paraneoplastic APS have been reported in malignancy, and obstetric APS cohorts suggest a possible bidirectional relationship with cancer incidence. In conclusion, the malignancy-aPL interface involves increased antibody prevalence, phenotype-dependent thrombotic risk, CAPS association, and paraneoplastic mechanisms. Clinical interpretation must consider antibody profile and persistence, avoiding conclusions based on isolated positivity. Prospective studies are needed to clarify clinical relevance and guide screening strategies. Cite this article as: Carvalho JFd, Amadei LP, Rodrigues CEM. A dangerous partnership: malignancy and antiphospholipid antibodies. Eurasian J Med. 2026, 58(4), 1434, doi: 10.5152/ eurasianjmed.2026.261434.