Thin malignant melanomas and recurrence potential
H. M. Shaw, W. H. McCarthy, S. W. McCarthy and G. W. Milton
Sydney Melanoma Unit, Department of Surgery, University of Sydney, Camperdown, Australia.
Of 846 patients with stage I malignant melanoma that was less than 0.76-mm
thick who were followed up for two to 31 years, 61 (7.2%) developed a
recurrence. For those patients who did not initially undergo an elective
lymph node dissection, the majority of first recurrences were at regional
lymph nodes. Attempts have been made to identify those patients at risk of
relapsing. Axial lesions, particularly those on the scalp, had the highest
recurrence rate, with 15% of all thin scalp lesions recurring compared with
only 4% of all thin extremity lesions. Three histological features proved
to be useful prognostic indicators when analyzed by single-factor analysis.
Evidence of ulceration in the primary lesion increased the recurrence rate
from 6.7% to 26.1%. While only 4.3% of lesions displaying low mitotic
activity recurred, this rate rose to 23.8% for those lesions of a high
mitotic grade. Only 5% of Clark's level II lesions recurred, compared with
about 12% of lesions at either level III or IV. Evidence of regression in
thin lesions had no deleterious effect on prognosis. This study defines a
small subset of patients who may benefit from elective lymph node
dissection.
