Rose-Lynn McCarthy¹, Christina Brown^2,3, Sandra O’Toole^1,3, Timothy Fielder¹, Sunaina Anand¹, Sanjay Warrier^3,4, Wendy A Cooper^1,3,5

¹Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, NSW Health Pathology Camperdown NSW Australia 

²Department of Haematology, Royal Prince Alfred Hospital, Camperdown NSW, Australia

³Faculty of Medicine and Health, University of Sydney, Sydney, NSW, Australia.

⁴Department of Breast Surgery, Chris O’Brien Lifehouse, Camperdown, New South Wales, Australia 

⁵School of Medicine, Western Sydney University, Sydney, NSW, Australia.

 

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytic disease of an undefined progenitor cell. The disease has a myriad of clinical manifestations with diverse organ system involvement, particularly in the long bones as well as the perinephric and periaortic spaces. Histologically, ECD is characterised by a proliferation of mature typically foamy histiocytes in a background of inflammatory stroma. The disease is often driven by BRAF V600E mutations, reported in 54% of cases¹ and can follow a previous diagnosis of Langerhans cell histiocytosis (LCH).

 

We present a case of a 60yo woman with a history of prior duodenal LCH who presented with ECD in the unusual location of the chest wall surrounding breast implants, and initially thought to represent a florid reaction to ruptured implants. The lipid laden foamy macrophages of the disease obscured detection of BRAF V600E expression by immunohistochemistry whilst further molecular testing confirmed a BRAF V600E mutation, leading to the diagnosis of mixed histiocytosis (ECD/LCH). This highlights the importance of considering BRAF V600E molecular testing if ECD is suspected, especially given the history of prior LCH. A positive result can open up treatment options for patients and establish a risk profile for frequency of follow up and survival.

¹ Haroche, J., Charlotte, F., Arnaud, L., et al. (2012). High prevalence of BRAF V600E mutations in Erdheim-Chester disease but not in other non-Langerhans cell histiocytoses. Blood, 120(13), 2700–2703