Table 2.
Amelanotic vs. Pigmented Melanoma | ||||||||
---|---|---|---|---|---|---|---|---|
Pigmented Melanoma | Amelanotic Melanoma | Study Design Featuresb | Study Design Features + Phenotypec | Study Design Features + Phenotype + MC1Rd | ||||
Characteristics | (n = 2209)a | (n = 178)a | OR (95% CI) | P Valuee | OR (95% CI) | P Valuee | OR (95% CI) | P Valuee |
Phenotype | ||||||||
Back nevi | ||||||||
Present | 1904 (86.2) | 139 (78.1) | 1 [Reference] | 0.006 | 1 [Reference] | 0.01 | 1 [Reference] | 0.01 |
Absent | 305 (13.8) | 39 (21.9) | 1.76 (1.18–2.65) | 1.71 (1.14–2.57) | 1.68 (1.12–2.53) | |||
Freckles | ||||||||
None to few | 1912 (86.6) | 143 (80.3) | 1 [Reference] | 0.007 | 1 [Reference] | 0.03 | 1 [Reference] | 0.10 |
Many | 297 (13.4) | 35 (19.7) | 1.76 (1.17–2.65) | 1.58 (1.04–2.39) | 1.44 (0.93–2.22) | |||
Phenotypic indexf | ||||||||
Sun-resistant phenotypic index | 989 (47.1) | 68 (38.2) | 1 [Reference] | 0.006 | 1 [Reference] | 0.02 | 1 [Reference] | 0.03 |
Sun-sensitive phenotypic index | 1109 (52.9) | 110 (61.8) | 1.57 (1.14–2.18) | 1.48 (1.07–2.07) | 1.44 (1.03–2.01) | |||
Genetics | ||||||||
MC1Rg | ||||||||
wt/wt | 357 (16.2) | 23 (12.9) | 1 [Reference] | - | - | 1 [Reference] | ||
r/wt or R/wt | 980 (44.4) | 69 (38.8) | 1.17 (0.71–1.93) | - | - | 1.16 (0.70–1.92) | ||
r/r, R/r, or R/R | 872 (39.5) | 86 (48.3) | 1.70 (1.04–2.78) | - | - | 1.43 (0.86–2.39) | ||
P value for trend | 0.01 | - | - | 0.13 |
Abbreviations: CI, confidence interval; GEM, genes, environment, and melanoma; MC1R, melanocortin 1 receptor; MPM, multiple primary melanoma; OR, odds ratio; SPM, single primary melanoma.
Data are given as number (percentage) of melanomas unless otherwise specified.
Adjusted for study design features: sex, age, study center, and lesion status (SPM or index MPM)
Adjusted for study design features, freckling, back moles, and phenotypic index.
Adjusted for study design features and all characteristics displayed in the table.
P values were calculated according to logistic regression models and P values for trend were calculated including MC1R categories as ordinal variables.
Phenotypic index was calculated by additively combining: hair color (black or dark brown=0; light brown or blonde=1; red=2), eye color (brown=0; grey, green, or hazel=1; blue=2), and ability to tan (deeply or moderately=0; occasionally or none=1). Those with index scores of 0,1, or 2 were categorized as having a sun-resistant phenotypic index. Patients with index scores of 3, 4, or 5 were categorized as having a sun-sensitive phenotypic index.
MC1R “R”: D84E, R142H, R151C, R160W, and D294H, all nonsense and insertion/deletion; “r”: all other variants; “wt”: consensus.