Intracellular Aspergillus niger conidia in alveolar macrophages: A diagnostic clue in a lung transplant recipient

Bronchoalveolar lavage (BAL) is a basic diagnostic method for the detection of fungal infections in lung transplant recipients. Aspergillus species are frequently identified, typically by the presence of septate hyphae; however, the visualization of conidia in cytologic preparations is rare. Aspergillosis caused by Aspergillus niger is an uncommon but recognized infectious complication in this patient population.We report on the case of a 60-year-old lung transplant recipient who underwent routine surveillance bronchoscopy eight weeks post-transplantation in August 2025. A substantial amount of adherent secretion was noted at the medial part of the right bronchial anastomosis. Surveillance BAL was performed from the right S8 segment, and cytospin preparations revealed intracellular Aspergillus conidia within alveolar macrophages. Galactomannan antigen assay was negative; however, fungal culture confirmed A. niger after five days.This case highlights the diagnostic value of identifying fungal conidia in BAL cytology, which may facilitate early recognition of invasive fungal infection or fungal colonization potentially leading to invasive disease or facilitate chronic lung allograft dysfunction (CLAD) development.