Sentinel lymph nodes in malignant melanoma: extended histopathologic evaluation improves diagnostic precision.
BACKGROUND
The optimal technique for sentinel lymph node (SN) assessment in patients with melanoma is controversial. Molecular analysis (reverse transcriptase-polymerase chain reaction) detects significantly greater numbers of SNs with suspected micrometastases (up to 71%) than does routine histopathology (approximately 20%). The authors sought to identify possible reasons for this discrepancy and to determine whether using an extended histopathologic protocol could improve diagnostic precision.


METHODS
Two hundred thirty-one SNs from 100 consecutive patients with cutaneous melanomas that measured 1-4 mm in thickness were bisected, and half of the lymph node was examined according to an extensive histopathologic protocol involving serial sectioning and immunohistochemical analysis of 3 melanocyte-associated markers (S-100, HMB-45, and Melan-A).


RESULTS
Lymph node melanocytic lesions were frequent, with micrometastases and benign nevus inclusions (BNI) found in SNs in 28% and 28% of patients, respectively (4 SNs contained both). Melan-A was the most sensitive immunohistochemical marker and was positive in all BNI-positive SNs and 97% of micrometastasis-positive SNs. Although HMB-45 showed differential labeling in micrometastases compared with BNI (82% vs. 16%), immunohistochemistry could not distinguish between those lesions. Micrometastases were already identified on the first central level in 49% of positive SNs, whereas only 23% of SNs with BNI were diagnosed on the first level.


CONCLUSIONS
Extensive serial sectioning with immunohistochemical analysis substantially increased the histopathologic detection of micrometastases and BNI in melanoma SNs to a level approaching the level reported for molecular techniques. The large number of BNIs represents an important potential source of imprecision (false positivity) in SN assays based on nonmorphologic methods.
Abrahamsen
Helene Nortvig
HN
Institute of Pathology, Aarhus Kommunehospital, Aarhus University Hospital, Aarhus, Denmark. abrahamsen@dadlnet.dk
Hamilton-Dutoit
Stephen J
SJ
Larsen
Jørn
J
Steiniche
Torben
T
D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008545:Melanoma / Q000175:diagnosis* / Q000473:pathology*; D008875:Middle Aged; D009362:Neoplasm Metastasis / Q000175:diagnosis*; D009367:Neoplasm Staging / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021701:Sentinel Lymph Node Biopsy / Q000379:methods*; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000473:pathology*