Beta 1 integrin expression in malignant melanoma predicts occult lymph node metastases

Area of Science:

• Oncology
• Dermatology
• Molecular Biology

Background:

• The role of elective lymph node dissection (ELND) in malignant melanoma management remains debated.
• Experimental data suggest beta1 integrins may promote melanoma metastasis, but clinical relevance in humans is unknown.

Purpose of the Study:

• To investigate the clinical significance of beta1 integrin expression in primary cutaneous melanoma.
• To determine if beta1 integrin expression correlates with the likelihood of regional lymph node (LN) metastases.

Main Methods:

• Analysis of primary cutaneous melanoma samples from 76 patients who underwent ELND.
• Quantification of beta1 integrin expression using an image analyzer to determine the percentage of tumor area stained.

Main Results:

• Beta1 integrin was expressed in all tumors from patients with positive lymph nodes (LNs) versus 26% of those with negative LNs (p < 0.001).
• Patients with beta1 integrin-positive tumors had a 62% rate of LN metastases, compared to 0% for negative tumors (p < 0.001).
• Tumor area staining of >=10% for beta1 integrin strongly predicted LN metastases (91% of cases with metastases vs. 8% without, p < 0.001).

Conclusions:

• This study establishes the first correlation between a molecular marker (beta1 integrin) in primary melanoma and regional LN metastasis risk.
• Beta1 integrin immunostaining of >=10% of tumor area is a reliable predictor of occult LN metastases.
• This marker can help identify patients likely to benefit from ELND.