Apoptosis in seborrheic keratoses: an open door to a new dermoscopic score

Abstract

The aetiology of seborrheic keratoses (SK), the most common benign epithelial tumours, and any relationship with malignancy are not yet known. As a protective anti-cancer mechanism, apoptosis reflects cellular loss as a reaction to proliferative activity. The objective of this study was to quantify apoptosis in different SK types (acanthotic, hyperkeratotic, reticulated, irritated and clonal) and correlate the dermoscopic picture with apoptosis rate. After a qualitative and quantitative analysis of dermoscopic images, we defined a new quantitative dermoscopic score (C3V2F, crypts, millia cysts, colours, hairpin vessels, irregular vessels, fissures) from 0 to 22, which enabled us to establish cut-offs correlating with apoptosis rates. All five SK forms were associated with lower apoptosis rates compared with normal skin. A C3V2F score >10 and greater number of crypts and colours reflected a higher apoptosis rate, which implies a benign character of evolution. In contrast, the presence of irregular vessels on more than 50% of the lesion surface implied a lower rate of apoptosis and probably associated with a risk of malignant transformation. On the basis of dermoscopic information, we used multiple regression to establish a model for estimating the rate of apoptosis with a 0.7 prediction interval (approximately 1S.D.). The new C3V2F score could be valuable for the clinical evaluation of possible SK prognosis and decisions regarding excision.

Fig 2

The five main subtypes of seborrheic keratosis. Pathological pictures are 10×, HE stain

Fig 3

Different histopathological types of seborrheic keratosis stained for the identification of apoptotic cells. PI, propidium iodide; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling. Note the condensed and bright apoptotic nuclei stained with PI and the brownish nuclei of apoptotic, TUNEL-positive cells. The inserts show clusters of apoptotic cells around corneous globes and vessels.

Fig 4

(A) Percentages of apoptotic cells identified by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) in normal skin and different histopathological variants of seborrheic keratoses. Bars indicate the standard error of the mean (S.E.M.). *P < 0.05, anova with Dunnett post-hoc test. (B) Percentage of TUNEL-positive cells decreases as the case scores below the cut-off in an increasing number of dermoscopic scores. Error bars indicate the S.E.M.. (C) Percentage of TUNEL-positive cells grouped by dermoscopic scores predicting low rates of apoptosis (‘bad’ scores). (−1) denotes controls. Note that the presence of at least one ‘bad’ score (regardless of the score) is associated with a decreased rate of apoptosis from a normal of approximately 38–19%, whereas the case with no ‘bad score’ has an apoptosis rate in the range of controls. Note the additional drop in apoptosis rate from 2 to 3 ‘bad scores’, which justifies the grouping as presented. The insert shows the proportion of cases in our cohort with at least 1 (1+), 2 (2+), etc. ‘bad’ scores. Error bars indicate the S.E.M.

Fig 5

Significance (P value) of quantitative parameter cut-offs included in the C3V2F score. ‘Total score’ (C3V2F) refers to the added values of parameters a–f (crypts, millia-cysts, hairpin vessels, colour, fissures and irregular vessels). ‘Total vessels’ refers to added values of parameters quantifying vessels (hairpin vessels and irregular vessels). In the graphs, the average percentage of apoptotic cells in the populations separated by the cut-offs is represented. Bars indicate the S.E.M. and significance is determined as P < 0.05 (anova with Dunnett post-hoc test).

Fig 6

Correlation graphs of the percentage of apoptotic cells (TUNEL-positive), ‘composite’, ‘total without vessels’ and ‘vessels’ scores. The numbers in the upper panels represent the Pearson correlation coefficient, r. The ‘total without vessels’ score is defined as the sum of parameters a (crypts), b (millia cysts), d (colours) and e (fissures) of the C3V2F score. The ‘total vessels’ score is defined as the sum of parameters c (hairpin vessels) and f (irregular vessels) of the C3V2F score. The ‘composite score’ is defined as the difference between ‘total without vessels’ and ‘vessels’ scores. The bottom panel shows the green framed upper panel in detail, the formula of the multiple regression model, and the prediction interval of 0.7.