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Excisional biopsy best for diagnosing melanoma

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – Excisional biopsies are best for diagnosing cutaneous melanoma, because partial biopsies have higher risks of misdiagnosis, adverse events, and microstaging inaccuracy, Australian researchers report.

Excisional biopsy is the recommended technique for suspected melanoma, but many dermatologists still routinely use partial biopsies instead, according to senior author Dr. John W. Kelly, from Monash University, Melbourne, and colleagues.

In the Archives of Dermatology for March, the researchers report on 2470 patients with histologically confirmed melanoma who came to their tertiary referral center for treatment. The referring physicians had based their diagnoses on results of punch biopsy in 163 cases, shave biopsy in 180 cases, or excisional biopsy in 2127 cases.

Overall, 2252 diagnoses were correct (91%), 135 were false positives (6%), and 83 were false negatives (3%), including 37 tied to an adverse outcome.

Relative to excisional biopsy, punch and shave biopsy increased the odds of misdiagnosis by 16.6- and 2.6-fold, respectively (p < 0.05 for both). Moreover, punch biopsy increased the risk of a misdiagnosis with adverse outcome by 20-fold (p < 0.001).

Other risk factors for misdiagnosis included acral lentiginous melanoma, desmoplastic melanoma, and nevoid melanoma.

The rates of inaccurate microstaging among correctly diagnosed cases were 34% with punch biopsy, 19% with shave biopsy, and 9.1% with excisional biopsy. Thus, relative to excisional biopsy, punch and shave biopsy increased the odds of inaccurate microstaging by 5.1- and 2.3-fold, respectively (p < 0.001 for both).

When partial biopsy was performed, the risk of microstaging inaccuracy climbed by 1.8-fold for each 1-mm increase in tumor thickness (p < 0.001).

The researchers also found that misdiagnosis was more likely when general practitioners first managed the patients, rather than dermatologists.

In an editorial, Dr. Ashfaq A. Marghoob and colleagues from Memorial Sloan-Kettering Cancer Center, New York, point out that in many areas, patients don’t have access to dermatologists, and they emphasize the need for dermatologists and general practitioners to work together in diagnosing melanoma.

“The battle against melanoma cannot be won without dermatologists actively encouraging, educating, and soliciting the help of general practitioners,” the editorialists state.

Arch Dermatol 2010;146:234-239,325-328.