The diagnostic role of transbronchial lung cryobiopsy in inflammatory myeloid neoplasms

<bold>Background</bold> Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD) are rare inflammatory myeloid neoplasms (IMNs) that may primarily affect the lungs. A definitive diagnosis of IMNs is mostly obtained through surgical lung biopsy (SLB). However, transbronchial lung cryobiopsy (TBLC) in diffuse parenchymal lung diseases offers important diagnostic information with no need for hospital stay and fewer major adverse events compared to SLB. <bold>Aim</bold> to evaluate the diagnostic role, feasibility and safety TBLC in IMNs. <bold>Methods</bold> between 2014 and 2023, 16 cases of IMNs were histologically confirmed using TBLC in our department. We retrospectively collected clinical, functional and histological data. <bold>Results</bold> samples obtained by TBLC were all considered adequate, and histological features characteristic of IMNs were found in all 16 patients, comprising 14 cases of LCH and 2 of ECD. 11 (68%) patients were female and 5 (32%) were male, with a median age of 43 (21-78). All patients had a history of active or former smoking. At diagnosis, the forced vital capacity (FVC) was 95% (70-125), and the diffusion capacity of the lungs for carbon monoxide (DLCO) was 67% (48-83). All LCH histological samples showed immunohistochemistry positivity for CD1a, S-100 and 4 patients had BRAF mutation; all the 2 ECD cases showed CD68+ and BRAF mutation. Pneumothorax occurred in 3(18%) patients, all of whom were managed with drainage tube placement. Minor bleeding was reported in 1(6%) patient during the procedure. <bold>Conclusion</bold> TBLC is a safe and minimally invasive approach for characterizing IMNs, providing high diagnostic confidence and a low rate of complications.