A modified vimentin histological score helps recognize pulmonary sarcomatoid carcinoma in small biopsy samples

Background: As pulmonary sarcomatoid carcinomas (PSCs) are life-threatening tumors, an improvement in their recognition in small-sized tumor samples is clinically warranted. Materials and Methods: Preoperative biopsy samples and paired surgical specimens from 20 pleomorphic carcinomas, two pulmonary blastomas and one carcinosarcoma (training set) were studied for vimentin immunohistochemistry. A modified vimentin histologic score (M-VHS) was devised by multiplying three independently assessed parameters, i.e. the percentage of positive cells (from 0 to 5+, by quintiles), the intensity of immunostaining (low=1 vs. strong=2) and the distribution pattern within the cytoplasm (partial=1 vs. diffuse=2), so ranging from 0 to 20. Forty-eight consecutive and independent cases of non-small cell lung carcinoma (NSCLC), including two additional cases of PSC, were used as control groups (validation set). Results: No differences in M-VHS were found between biopsies and surgical specimens of PSC, thus confirming the occurrence of stable epithelial mesenchymal transition (EMT) and hence the specific diagnosis of PSC. All types of PSC shared the same M-VHS. The M-VHS of 46 conventional NSCLC was by far lower (p<0.0001), whereas two additional cases of PSC showed the same results as the training set. Poorly differentiated NSCLC with marked pleomorphism but not stable EMT did not exhibit significantly increased M-VHS values. Conclusion: M-VHS helped in morphological analysis to render more definite diagnoses on small biopsies of PSC.