Different clinical behavior of nodular melanoma (NM) compared to superficial spreading melanoma (SSM) at New York University from 1972 to present.

Abstract:

Background: The high recurrence and mortality rates associated with NM are generally attributed to its advanced thickness at presentation; nevertheless, we and others have recently reported that NM may have distinct biologic characteristics independent of thickness. Here, we examine the differences in clinical behavior of NM compared to SSM at NYU, a tertiary referral center, over three decades. Methods: 1,684 melanoma patients (pts) prospectively enrolled were studied. 1,143 pts were diagnosed 1972-1982 (median thickness 1.3mm; 793 (69%) SSM, 126 (11%) NM, and 224 (20%) other). 541 pts were diagnosed 2002-present (median thickness 0.9mm; 299 (55%) SSM, 125 (23%) NM, 117 (22%) other). Differences between the features of NM and SSM within each time period as well as changes over time were analyzed using the t-test, Wilcoxon rank-sum test, or chi-square test, as appropriate. Results: Median age at diagnosis of NM increased from 51 years of age in 1972-1982 to 63 years of age in the current time period (p<0.01). No significant stage migration or change in median NM thickness over time was observed. In comparison, SSM pts in the current time period are diagnosed at earlier stages and as thinner lesions (p<0.01 and p<0.01, respectively). The rate of ulcerated NMs did not significantly change over time (p=0.29), while the proportion of ulcerated SSMs decreased significantly (p<0.01). The rate of lymph node positivity was 21.3% in NM pts in the current time period compared to only 11.3% in SSM pts (p=0.04), however this was insignificant after controlling for tumor thickness (p=0.76). Nevertheless, 20% (17/85) of NM pts who had negative sentinel lymph node biopsies (SLNB) and/or completion dissections later developed recurrent disease, compared to 3.9% (4/102) of SSM pts (p<0.01). Conclusions: Our data suggest that NM presents with aggressive histological features and advanced stages of disease that may not be solely attributed to thickness. Older patients may need more frequent screening for NM. Furthermore, SLN status may not accurately predict risk of metastasis in these patients. The distinct clinical behavior of NMs supports further research into the underlying biologic differences among histopathologic subtypes.

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