Identification of lymph node metastases by use of polymerase chain reaction (PCR) in melanoma patients.

Diagnosis of clinically suspected lymph node metastases in melanoma patients can be confirmed with high sensitivity and specificity by fine needle aspiration (FNA) cytology. However, small lymph nodes or haemorrhagic metastases may yield negative or unevaluable cytology. We tested whether the sensitivity and specificity of presurgical diagnosis could be improved by a polymerase chain reaction (PCR) method, identifying tyrosine-mRNA in samples obtained by fine needle aspiration (FNA-PCR). PCR was positive in 17 of 18 histopathologically proven melanoma metastases, while conventional cytopathology detected 16 of 18. 4 of 9 disease-free melanoma patients with negative FNA cytology had positive PCR results, but controls gave negative results. FNA-PCR analysis cannot be recommended as superior to conventional FNA cytological examination. Whether the positive FNA-PCR in four of the nine clinically unsuspicious regional lymph nodes correlates with earlier disease progression or indicates lower specificity of the method will need further investigation.