A 70-year-old man with past medical history of prostate cancer status post prostatectomy and long-standing history of smoking was found to have a 1.5 cm right upper lobe nodule on a surveillance chest CT scan. A bronchoscopic biopsy yielded non-diagnostic findings and a right upper lobe wedge resection was performed. Grossly, the lung wedge contained a 1.5 x 1.2 x 1.1 cm tan-white, dense fibrous lesion with ill-defined borders. Frozen section evaluation showed dense fibrosis/scar and no malignancy. Permanent tissue sections confirmed a nodule composed of dense fibro-collagenous tissue with jagged borders (Figure 1). No leaf-like growth pattern was observed at the periphery of the lesion (Figure 2). In addition, the nodule contained focal mature adipose tissue, entrapped benign small airways and clefts of alveoli with reactive pneumocytes and few entrapped blood vessels (Figures 2, 3 and 4). Inflammation, calcifications, necrosis, atypia, and/or malignancy were not identified. Masson’s trichrome highlighted the collagenous stroma in blue and short fascicles of benign smooth muscle in red (Figure 5). By immunohistochemistry, the nodule was negative for STAT6 (not shown), with entrapped pneumocytes positive for TTF1 (Figure 6).

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