Malignancy in Systemic Sclerosis: A Multicenter Retrospective Study

<b>Background/Objectives</b>: Systemic sclerosis (SSc) is associated with high malignancy risk. With improving SSc management, tumor risk could change, therefore re-evaluating the possibility of neoplasms is necessary. Our aim was to observe malignancy prevalence and its risk factors in the Hungarian SSc population, comparing them to our previous and international results. <b>Methods</b>: We retrospectively collected the data of SSc patients followed by and admitted to three Hungarian clinical centers between 2018 and 2024. The collected data included the characteristics of SSc and neoplasms, autoantibody positivities, immunosuppressive treatments, pregnancy and environmental factors. <b>Results</b>: Out of 541 patients, 85 had malignancy and, in total, 96 tumors were registered. Skin cancer was the most common (<i>n</i> = 24), followed by breast (<i>n</i> = 14) and lung cancer (<i>n</i> = 14). Among skin cancers, almost one-third was melanoma. Tumors mostly appeared in two peaks: around the time of SSc diagnosis and 10 years later. The occurrence of anti-RNA Polymerase III (anti-RNAPIII) was significantly higher in cancerous patients. Tumor risk was higher with anti-RNAPIII (Odds Ratio (OR) 4.33, 95% Confidence Interval (95% CI) 1.08, 15.1) and anti-topoisomerase I (ATA) (OR 2.34, 95% CI 0.94, 5.84) positivity. Women and patients with diffuse cutaneous SSc (dcSSc) were more likely to have malignancy. Smoking (OR 1.27, 95% CI 0.53, 3.00) also raised the possibility of carcinogenesis. Cancerous patients were older (<i>p</i>-value = 0.003), and their mortality was worse compared to non-cancerous patients (Hazard Ratio (HR) 4.75, 95% CI 2.12, 10.62). Pregnancy did not provide a protective effect against breast cancer. <b>Conclusions</b>: Malignancy significantly contributes to the increased mortality in SSc. Female gender, dcSSc, anti-RNAPIII positivity, smoking and older age represent a higher risk of tumors. Dermatological cancer screening is necessary for all patients with SSc.