Histologic staging in malignant melanoma: cross-sectional area revisited

Tumor thickness is considered the single most important predictor of survival in clinically localized malignant melanoma. A recent study found tumor volume a more sensitive predictor of survival than thickness. Volume measurement, however, is complicated, time consuming, and based on biologically imprecise mathematical models of tumor configuration. This report compares the prognostic power of cross-sectional area (CSA), a simpler measurement than volume, with tumor thickness.

Forty-five patients with clinically localized malignant melanoma and a minimum 5-year follow-up post excision with negative resection margins were retrospectively followed for disease recurrence or death. Digitalized histologic images of each tumor were made from the original pathology slides and stored on a compact disc. Maximum tumor thickness and CSA were calculated for each primary melanoma using an image analysis program and compared for predictive accuracy of 5-year survival.

CSA was positively correlated with maximum tumor thickness (r = 0.76). Both measures had a similar predictive accuracy for survival. Patients with melanomas less than 8 mm2 had superior 5-year (94%) and disease-free survival rates (78%) compared to patients with melanomas exceeding 8 mm2 (5-year survival, 62%; 5-year disease-free survival, 23%).

CSA is an easily calculated measurement that is as predictive for 5-year survival as is Breslow's thickness. Prospective assessment of CSA is warranted.