Therapy-induced morphological changes in lung cancer

Especially patients with locally advanced non-small cell lung cancer, but also patients with small cell lung cancer without distant metastases are increasingly treated by means of neoadjuvant multimodality therapy. In corresponding resection specimens of primary tumours and lymph nodes, the extent of therapy-induced tumour regression represents an independent prognostic factor. After neoadjuvant therapy, different-sized target-like foci with central necrosis, adjoining narrow foam cell rim, peripheral vascular granulation tissue and transition into a marked scarry fibrosis can be established in the former tumour area. Morphological changes indicating therapy-induced tumour regression can be graded according to the "Bochum regression grading" system. Cytomorphological changes do not allow reliable conclusions to be drawn about the success of the applied neoadjuvant therapy. In resection specimens, they should not form the basis of a cytopathologic grading or lead to the diagnosis of "large cell anaplastic carcinoma".