Thin cutaneous malignant melanomas (< or =1.5 mm): identification of risk factors indicative of progression.
BACKGROUND
Although thin cutaneous melanomas generally have a favorable prognosis, in some cases they may undergo progression. The current study was undertaken to identify variables that may predict a more aggressive clinical outcome in these patients. In addition to classic clinicopathologic features, the authors tested the prognostic impact of three new morphometric quantitative parameters: 1) tumor thickness plus regression thickness (T+R), 2) percentage of skin thickness infiltrated by tumor cells (T/S ratio), and 3) percentage of skin thickness infiltrated by tumor cells and regression ([T+R]/S ratio).


METHODS
The authors retrospectively evaluated 287 patients with invasive cutaneous melanoma < or = 1.5 mm in thickness. Disease free survival rates (Kaplan-Meier method) were compared by using the log rank test. A multivariate analysis (Cox proportional hazards model) was used to determine the independent effect of each variable on progression. Progression was defined as any documented cutaneous local and/or distant metastasis.


RESULTS
Thirty-two of the 287 patients (11.1%) underwent disease progression. The overall 5-year and 10-year disease free survival rates were 89.3% and 84.6%, respectively. In the univariate analysis, the following factors were found to be significant predictors of progression: male gender (P = 0.01), acral-lentiginous histotype (P = 0.02), tumor thickness (P = 0.005), T+R (P = 0.001), T/S ratio > or = 50% (P = 0.03), (T+R)/S ratio > or = 50% (P = 0.006), vertical growth phase (P = 0.04), and absence of inflammatory response (P < 0.0001). Conversely, age, site, and Clark's level did not affect the risk of recurrences and/or metastases significantly. In the multivariate analysis, only T+R (P = 0.009) and inflammatory response (P < 0.0001) were found to be independent predictors of progression. Five-year disease free survival rates according to presence versus absence of inflammatory response were 93.4% and 63.8%, respectively (P < 0.0001).


CONCLUSIONS
In the current study, peritumoral and intratumoral inflammatory infiltrate and T+R were found to be strong independent predictors of progression in thin cutaneous melanomas.
Massi
D
D
Istituto di Anatomia e Istologia Patologica, Università degli Studi di Firenze, Italia.
Franchi
A
A
Borgognoni
L
L
Reali
U M
UM
Santucci
M
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D006801:Humans; D007249:Inflammation; D008297:Male; D008545:Melanoma / Q000473:pathology* / Q000556:secondary; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D012878:Skin Neoplasms / Q000473:pathology*; D016019:Survival Analysis