DIP-like Adenocarcinoma Presenting as a Part-Solid Nodule: A Case Report

Pure ground-glass and part-solid lung nodules are becoming increasingly appreciated as harbingers of malignancy. However, occasionally diagnostic biopsies can demonstrate unexpected findings that may lead to a misleading diagnosis and clinical confusion. Here we present the case of a 70-year-old Taiwanese man with a light smoking history (10-20 pack years), emphysema, and childhood-treated tuberculosis who presented with a part-solid nodule that was diagnosed as a very rare case of adenocarcinoma of the lung with <i>desquamative interstitial pneumonia</i> (DIP)-like microscopic morphology. DIP is a non-neoplastic interstitial lung disease which presents as a diffuse and bilateral process and primarily occurs in smokers. When the morphologic pattern of DIP presents as a focal process, usually around bronchioles, it is labeled <i>respiratory bronchiolitis</i>. (RB)- a very common entity and almost universal in patients with significant smoking history. We describe this case to help educate and guide pathologists on the existence of this very rare entity and to consider performing lung cancer immunohistochemical markers whenever faced with this unexpected histological pattern in a pulmonary nodule.