Adenocarcinoma of the lung mimicking inflammatory lung disease with honeycombing

Pulmonary adenocarcinoma of the lung and its variants are well-defined entities, since the recent WHO classification of lung tumours. However, scant descriptions have been allocated to associated stromal changes, such as prominent inflammation and fibrosis, which can overshadow a tumoral proliferation and masquerade as a benign reactive process and this has not been recognised as a histopathological variant. The case of a 72-yr-old farmer who presented a multifocal well-differentiated adenocarcinoma that mimicked honeycomb lung with bronchiolectasis radiologically, on computed tomography scan and histologically at open lung biopsy, is reported. Histological pitfalls in the biopsy were represented by mild atypical cuboidal or columnar epithelial cells lining bronchiolar structures resembling florid bronchiolar metaplasia in a background of extensive fibrosis and inflammation, features that mimicked inflammatory honeycombing. However, histological analysis of the surgical resection of the main lesion, performed because of a clinical alteration of the patient, confirmed the diagnosis of multifocal adenocarcinoma of mixed subtype. A monomorphic proliferation of clear cells, lack of associated ciliated or squamous cells and presence of significant cytologic atypia gave a diagnosis of malignancy. This case illustrates how inflammatory and fibrotic changes may conceal a correct diagnosis of carcinoma and emphasises the importance of adequate sampling in such cases.