METHODS: This was a prospective single-center study of 2 years duration, during which 233 cases of endobronchial ultrasound guided aspiration of the intrathoracic lesions were examined. After excluding the cases without cellblock, with inadequate samples, with benign diagnosis, and excluding the lymphoma cases, finally 31 neoplastic cases were evaluated for expression of cytokeratin 19.
RESULTS: Diffuse cytoplasmic staining for CK19 was noted in nonsmall cell lung carcinomas (18/19 cases), while the expression in small cell carcinomas was low (2/5 cases). CK19 was also positive in mediastinal lymph node metastasis from a case each of papillary thyroid carcinoma, prostatic adenocarcinoma and infiltrating ductal carcinoma breast (1/2 cases). It showed focal faint staining in a case of mediastinal mesenchymal neoplasm and was negative in both the cases of primitive neuroectodermal tumor.
CONCLUSIONS: CK19 is a highly sensitive but nonspecific marker for nonsmall cell lung cancers. However, owing to diffuse staining pattern in most of these cases, role of its staining intensity as a predictor of prognosis could not be evaluated.