An objective measure of growth rate using partial biopsy specimens of melanomas that were initially misdiagnosed

Background: To calculate melanoma rate of growth (ROG), previous studies have relied on subjective patient recall to estimate time delay to diagnosis. Objective: To objectively calculate ROG by measuring the rate of increase in melanoma thickness between 2 sequential biopsy specimens over time. Methods: This was a retrospective review of 51 melanomas in which pathologic misdiagnosis of a partial biopsy specimen caused a delay before referral and excisional biopsy between January 1998 and January 2013. ROG was calculated as rate of increase in tumor thickness between biopsy specimens. Results: The median delay between the 2 biopsy specimens was 27 months (range, 3-89 months). Biopsy specimens of melanomas that were obtained initially in their in situ phase were thinner at excision compared to those that were first obtained as invasive tumors (median, 0.7 vs. 3.2 mm; P<.01) and had a lower ROG (median, 0.04 vs. 0.11 mm/month; P = .05). Faster growth was associated with increased tumor thickness, higher mitotic rate, symptoms, elevation, and amelanosis. Limitations: Partial biopsy specimens may not be representative of deepest tumor thickness. Conclusion: We have demonstrated an objective measure of melanoma growth rate using sequential biopsy specimens. The correlation between faster growth and aggressive tumor features supports what others have found and validates the historical measure of growth rate as a reliable clinical marker.