Beta₁ integrin expression in malignant melanoma predicts occult lymph node metastases

Background Elective lymph node dissection for malignant melanoma is still controversial. Experimental studies suggest that differential expression, activation, or both of β₁ integrins facilitate melanoma metastases. However, the clinical significance of β₁ integrin expression in human melanoma is unclear. Methods We examined primary cutaneous melanomas from 76 patients undergoing elective lymph node dissection. We quantified the percentage of tumor area stained by β₁ integrin antibody with an image analyzer. Results β₁ integrin was expressed in all 23 primary tumors from patients with pathologically positive lymph nodes (LNs) but in only 14 (26%) of 53 cases with pathologically negative nodes (p<0.001). No patients with β₁ integrin-negative tumors had LN involvement, whereas 23 (62%) of 37 patients with β₁ integrin-positive tumors had LN metastases (p<0.001). Furthermore, 21 (91%) of 23 cases with LN metastases but only 4 (8%) of 53 cases without had β₁ integrin staining of 10% or more of tumor area (p<0.001). Conclusions Our study is the first to show a correlation between expression of a molecular marker in the primary cutaneous melanoma and likelihood of regional LN metastases. β₁ immunostaining of 10% or more of tumor area reliably predicts patients most likely to harbor occult LN metastases and likely to benefit from ELND.