Histologic examination of the lesion revealed a superficial spreading melanoma invasive to Clark level IV, with a measured depth of 1.4 mm. Ulceration, regression, neurotropism, and vascular invasion were absent. No precursor lesion, tumor infiltrating lymphocytes, or microsatellites were identified. The mitotic rate was estimated at 1 mitosis per square millimeter.
On follow-up physical examination, the patient had no lymphadenopathy or hepatosplenomegaly. A chest radiograph demonstrated no abnormalities, and there was no evidence of metastases. A complete blood cell count was normal. The lesion was completely excised with a 2-cm margin of clinically normal skin. Sentinel lymph node mapping and a biopsy specimen from the right axilla did not show any evidence of metastatic melanoma (0 per 3 lymph nodes). The patient was without recurrence at the 6-month follow-up visit.