Endobronchial typical carcinoid with secondary Aspergillus fumigatus colonization: Avoiding a diagnostic pitfall in...

Endobronchial fungal colonization can obscure an underlying obstructive neoplasm in limited bronchoscopic biopsies, posing a significant diagnostic challenge. We report an immunocompetent 55-year-old woman presenting with an obstructing endobronchial mass whose bronchoscopic biopsy revealed a well-differentiated neuroendocrine neoplasm with abundant septate fungal hyphae confined to necrotic intraluminal debris. Tumour cells showed diffuse synaptophysin, chromogranin A, INSM1 and OTP expression with a Ki-67 proliferation index < 2%, supporting the diagnosis of a typical pulmonary carcinoid. Periodic acid-Schiff and Grocott-Gomori methenamine silver stains highlighted the fungal elements, while fungal culture confirmed Aspergillus fumigatus. The absence of fungal invasion within viable tumour, bronchial stroma or vascular structures favoured secondary colonization rather than tissue-invasive aspergillosis. This case highlights the importance of integrating histomorphology, ancillary investigations and microbiological findings, and emphasizes meticulous evaluation of viable tissue to avoid overlooking an underlying obstructing neoplasm.