KRT19 and neoplasm: This method detects cytokeratin 19 (CK19) mRNA amplification and allows classification of nodes into negative (<250 copies/mL of CK19 mRNA), presence of isolated tumor cells (>100 but <250 copies/mL), presence of micrometastases (>250 but <5000 copies/mL) or presence of macrometastases (>5000 copies/mL).