Systemic Sclerosis (SSc) is a chronic disease associated with a 1.5-fold increase in cancer risk, including lung cancer, hematological malignancies, and breast cancer (BC). This is a retrospective study aiming to explore the clinical and pathological features of BC developed by SSc patients. A total of 54.5% of patients developed BC before SSc (median interval: 5 years), whereas 45.5% of patients developed BC after SSc (median delay: 8 years). A total of 93.1% of patients were diagnosed with an early stage tumor. Among invasive carcinomas, 70.8% presented with a low Mib1, 8.3% with a tubular histotype, and 42.8% with a Luminal A-like phenotype. A total of 66.6% of patients underwent breast-conserving surgery and 55.5% RT. A total of 40% of patients developed interstitial lung disease after RT and 20% diffuse cutaneous SSc. The cause of death of the six deceased patients was PAH. A significant association was observed between the use of immunosuppressive therapy and diffuse skin extension, negative ACA, positive Anti-Scl-70, and interstitial lung disease, but not BC status. SSc patients developed BC at a good prognosis, suggesting a de-escalation strategy of cancer therapies. In particular, ionizing radiation and chemotherapeuticals should be limited to higher-risk cases. Finally, proper screening is mandatory in order to allow for early cancer detection in SSc patients.

Several authors reported an increased risk of cancer in SSc patients, including breast cancer (BC). Nevertheless, the mechanisms underlying this association have not yet been clarified. SSc and BC share several molecular pathways, which seem to play a common etiopathogenetic role. The previously published Sclero-Breast study demonstrated the development of BC with a good prognosis among these patients, which could be explained by an autoimmune background as a possible mechanism for limiting tumor extension. Here, we report the results of an IHC analysis of molecular pathways known to be common drivers for both diseases, with the aim to better define the mechanisms underlying a good prognosis of BC in patients affected by SSc. The analysis demonstrated higher TILs rates in all BC subgroups, with a high rate of PD-L1 expression especially in TNBC and HER2-positive BC, suggesting a less aggressive behavior in these patients compared to the general population. These results support a possible de-escalation strategy of cancer therapies in these fragile patients. These data could represent a starting point for future prospective studies based on the clinical application of these biomarkers with a larger sample size to promote a personalized and targeted oncological treatment for this specific subset of patients.