Solitary and multiple xanthogranulomas in adult patients: a single-center retrospective cohort study.

The systemic associations of adult xanthogranulomas (XGs), the most common subtype of non-Langerhans cell histiocytosis, are poorly understood. In this retrospective cohort analysis, we studied adult patients diagnosed with XGs and investigated the clinical features and systemic associations of adult XGs. Among 138 patients (mean age 43.3 years, 51.4% female, 76.8% white), adult XGs most frequently presented on the trunk (40.6%), differing from the pediatric predilection for the head and neck. Patients presenting with multiple XGs (3.6%) were significantly more likely to have systemic malignancies (p = 0.009), particularly hematologic malignancies (p = 0.001), as well as non-malignant hematologic disorders (p = 0.027). Hyperlipidemia (37%), cardiac disease (51.4%), and endocrine disease (31.2%) were the most prevalent systemic comorbidities. In conclusion, the presentation of multiple XGs in an adult is associated with malignancy (particularly hematologic malignancies) and non-malignant hematologic disorders, suggesting a possible link with immune dysregulation. Molecular testing in one patient with multiple XGs and CMML transformed to AML revealed the same KMT2a deletion in both the XGs and the bone marrow, raising the possibility of clonal relationships in some cases.