Incisional Biopsy for Melanoma Diagnosis

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Incisional Biopsy for Melanoma Diagnosis

Sometimes, only complete excision will do.

In most cases of melanoma, complete excisional biopsy is used to establish diagnosis and staging for prognosis and further management. Occasionally, partial excisional biopsies are done because the lesions are large or the suspicion of melanoma is low. In this prospective study, investigators followed 250 patients whose melanoma was diagnosed by incisional biopsy that removed less than half of the original lesion. Differences in lesion thickness between the incisional biopsy and the final, therapeutic excision were analyzed.

Mean melanoma thickness increased from 0.66 mm as indicated by partial incisional biopsy to 1.07 mm when determined by complete excision. In 21% of patients, the increase in actual Breslow depth resulted in an upstage; the mean increase in Breslow depth in the upstaged patients was 1.9 mm. Twenty-six patients who were upstaged (10% of all incisional-biopsy patients) became candidates for sentinel node biopsy when their lesion thickness was shown to be greater than 1 mm. The smaller the original biopsy relative to the size of the lesion, the more likely the patient was to be upstaged. Compared with lesions on the trunk, those on the limbs had higher odds of being upstaged; head and neck lesions had lower odds.

Comment: Partial incisional biopsy of melanoma underestimates thickness enough to affect prognosis in 21% of cases and to change lymph-node management in 10%. Incisional biopsies for melanoma diagnosis should be as large as possible, and if the final defect involves significant tissue rearrangement, surgeons should defer closure until they know the final Breslow depth of the lesion. In this way, accurate sentinel lymph-node biopsy can still be performed even after the final excision.

— George J. Hruza, MD

Published in Journal Watch Dermatology June 14, 2005