Pathologic assessment of melanoma sentinel nodes: a role for molecular analysis using quantitative real-time reverse transcription-PCR for MART-1 and tyrosinase messenger RNA.
OBJECTIVE
Molecular analysis of melanoma sentinel nodes (SN) is sensitive, but poorly specific because metastases cannot be distinguished from benign nevus inclusions (BNI). We investigated whether quantitative reverse transcription-PCR (RT-PCR) detection of MART-1 and tyrosinase mRNAs could improve this specificity and contribute to SN assessment.


METHODS
Two hundred twenty SNs from 95 melanoma patients analyzed by extensive immunohistopathology and real-time quantitative RT-PCR.


RESULTS
Using histopathology, SNs and patients were allotted to three diagnostic groups: (a) metastasis positive, (b) BNI positive, and (c) melanocyte-free. Median MART-1 and tyrosinase mRNA levels in SNs were significantly different in patients with metastasis compared with patients with BNIs (P < 0.05) and patients without melanocytic lesions (P < 0.001). However, a "gray-zone" was observed where distinction, based on mRNA levels, could not be made between the three groups. For both genes, the highest mRNA level recorded in each RT-PCR-positive patient was positively correlated with Breslow's tumor thickness. For SNs with metastases, tumor burden was significantly correlated to the mRNA level. Using the presence of a MART-1 RT-PCR signal to detect patients with metastases, a sensitivity of 100% and a negative predictive value of 100% were achieved when extensive immunohistology was used as reference.


CONCLUSIONS
Quantitative RT-PCR MART-1 and tyrosinase mRNA analysis cannot be used alone for SN diagnosis because of its poor specificity for melanoma metastasis. However, in approximately one third of cases without RT-PCR evidence of MART-1 expression, extensive histopathologic SN investigation is not necessary, thus substantially reducing the cost of SN analysis. The level of melanocyte-associated mRNA is associated with both tumor thickness and tumor burden as measured histopathologically, suggesting that this may be of prognostic value.
Abrahamsen
Helene Nortvig
HN
Institute of Pathology, Aarhus University Hospital, Aarhus Sygehus, Noerrebrogade 44, DK-8000 Aarhus C, Denmark. abrahamsen@dadlnet.dk
Sorensen
Boe Sandahl
BS
Nexo
Ebba
E
Hamilton-Dutoit
Stephen J
SJ
Larsen
Jørn
J
Steiniche
Torben
T
D000328:Adult; D000368:Aged; D000951:Antigens, Neoplasm; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008198:Lymph Nodes / Q000378:metabolism / Q000473:pathology*; D008207:Lymphatic Metastasis / Q000175:diagnosis / Q000235:genetics; D058965:MART-1 Antigen; D008297:Male; D008545:Melanoma / Q000235:genetics / Q000473:pathology*; D008875:Middle Aged; D014442:Monophenol Monooxygenase / Q000235:genetics; D009363:Neoplasm Proteins / Q000235:genetics; D011237:Predictive Value of Tests; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D021701:Sentinel Lymph Node Biopsy
D000951:Antigens, Neoplasm; D058965:MART-1 Antigen; C548667:MLANA protein, human; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D014442:Monophenol Monooxygenase