Fig. 4

CT Alternative Diagnosis with corresponding histopathology categorized as UIP. a Thin slice CT demonstrates upper and mid-zone predominantly reticulation, central bronchiectasis and mosaic attenuation with lobular lucency, classified as Alternative Diagnosis categorization by the 2018 ATS and Fleischner guidelines. The radiological diagnosis was favored to be chronic hypersensitivity pneumonitis. b Corresponding histopathology from the subsequent surgical lung biopsy shows all features required for categorization of UIP by both guidelines, including microscopic honeycombing. There was no evidence of airway-centered fibrosis, granulomatous inflammation, or other features suggesting alternative diagnosis. Hematoxylin and eosin (H&E) stain. Scalebar, panel B: 0.5 mm. Scalebar, inset: 0.1 mm