Q&A column, 3/18
March 2018—Our pathology group has an unusual case of residual squamous cell carcinoma of the lung in a lobectomy specimen after chemotherapy. The lung shows a hilar scar (1.7 cm) involving the lung parenchyma and the peribronchial adipose tissue. In the scar there is residual carcinoma (0.4 cm) that focally is involving the peribronchiolar adipose tissue around the lobar bronchus. The focus is located at 0.3 cm of the final surgical resection margin of the bronchus. Because the tumor involves peribronchiolar adipose tissue, is it considered outside the lung (extension outside the lung)? Since the tumor is in the mediastinal fat around the bronchi and had to invade the viscera pleura to invade the peribronchial adipose tissue, would the tumor stage be ypT2a? Or T3 since it is invading part of the mediastinal fat? Or should it be pT1?