Xanthomatous Inflammatory Infiltrate Involving the Spleen: An Unusual Presentation of Erdheim-Chester Disease and Review of the Literature.

BACKGROUND Erdheim-Chester disease (ECD) is a rare form of non-Langerhans cell histiocytosis characterized by foamy histiocytes, Touton-like giant cells, and fibrosis, typically affecting the diaphyseal and metaphyseal region of the long bones but that can involve any organ or tissue. ECD is usually associated with the BRAF V600E mutation or with other molecular mutations inserted in the MAPK cascade. CASE REPORT We present the case of a 63-year-old man with a previous history of myocardial infarction who underwent an emergency splenectomy for splenic rupture after an accidental fall. Histological examination of the spleen showed a diffuse xanthogranulomatous proliferation (CD68+, CD163+, S100-, CD1a-) with rare Touton-like giant cells in the red pulp. Based on the histologic findings, a diagnosis of ECD was made. However, skeletal involvement and BRAF V600E mutation were not detected. CONCLUSIONS Cases of non-Langerhans cell histiocytosis that are histologically consistent with ECD in unusual sites have been increasingly described. There is also anecdotal evidence for cases being associated with mutations besides BRAF V600E or with no genetic alteration and no skeletal involvement. Likewise, the spectrum of clinical and molecular features of ECD can be broader than previously considered. Furthermore, there is evidence that various phases of the disease can show different clinical presentations with distinct prognostic impact, according to the mutational spectrum. Recognizing ECD at an early stage allows more effective patient management, and pathologists and clinicians should be aware of the unusual clinical presentations of this rare condition.