The Impact Of Partial Biopsy On Histopathologic Diagnosis Of Cutaneous Melanoma

Objective: To compare partial and excisional biopsy techniques in the accuracy of histopathologic diagnosis and microstaging of cutaneous melanoma.Design: Prospective case series.Setting: Tertiary referral, ambulatory care, institutional practice.Patients: Consecutive cases from 1995 to 2006.Interventions: Partial and excisional biopsy. Other factors considered were anatomic site, physician type at initial management, hypomelanosis, melanoma subtype, biopsy sample size, multiple biopsies, and tumor thickness.Main Outcome Measures: Histopathologic diagnosis (false-negative misdiagnosis-overall or with an adverse outcome-and false-positive misdiagnosis) and microstaging accuracy. Odds ratios (ORs) and 95% confidence intervals (CIs) obtained from multinomial logistic regression.Results: Increased odds of histopathologic misdiagnosis were associated with punch biopsy (OR, 16.6; 95% CI, 10-27) (P<.001) and shave biopsy (OR, 2.6; 95% CI, 1.2-5.7) (P=.02) compared with excisional biopsy. Punch biopsy was associated with increased odds of mischagnosis with an adverse outcome (OR, 20; 95% CI, 10-41) (P<.001). Other factors associated with increased odds of misdiagnosis included acral lentiginous melanoma (OR, 5.1; 95% CI, 2-13) (P<.001), desmoplastic melanoma (OR, 3.8; 95% CI, 1.1-13.0) (P=.03), and nevoid melanoma (OR, 28.4; 95% CI, 7-115) (P<.001). Punch biopsy (OR, 5.1; 95% CI, 3.4-7.6) (P<.001) and shavebiopsy (OR, 2.3; 95% CI, 1.5-3.6) (P<.001) had increased odds of microstaging inaccuracy over excisional biopsy. Tumor thickness was the most important determinant of microstaging inaccuracy when partial biopsy was used (odds of significant microstaging inaccuracy increased 1.8-fold for every I mm increase in tumor thickness; 95% CI, 1.4-2.4) (P<.001).Conclusions: Among melanoma seen at a tertiary referral center, histopathologic misdiagnosis is more common for melanomas that have been assessed with punch and shave biopsy than with excisional biopsy. Regardless of biopsy method, adverse outcomes due to misdiagnosis may occur. However, such adverse events are more commonly associated with punch biopsy than with shave and excisional biopsy. The use of punch and shave biopsy also leads to increased microstaging inaccuracy.