Dermoscopy uncovers clinically undetectable pigmentation in basal cell carcinoma

The presence of pigmentation might influence the management of basal cell carcinoma (BCC), with pigmented BCC responding poorly to certain treatments. Clinical studies report on a generally lower frequency of pigmentation compared with dermoscopic and histopathological studies, but the true frequency at which pigmentation occurs in clinically nonpigmented BCC has not been studied in detail.

To compare the clinical and dermoscopic frequency of pigmentation in a series of histopathologically diagnosed BCCs and to correlate it with patient demographics, tumour location and histopathological subtype.

Clinical and dermoscopic images of histopathologically confirmed BCCs were retrospectively evaluated for the presence of pigmentation. Dichotomous outcome variables were clinically pigmented and dermoscopically pigmented BCC. All separate dermoscopic variables were included in the analysis. Differences in proportions were evaluated using Pearson's chi-square test.

Five hundred and seven BCCs from 507 patients with a mean age of 67 years and a male-to-female ratio of 1.35 : 1 were included in the study. Clinically, 295 tumours were judged as nonpigmented. Of those, dermoscopy disclosed pigmentation in 88 cases (29.8%). Overall, blue-grey ovoid nests were the most frequent dermoscopic pattern (n = 184, 36.3%), followed by multiple blue-grey dots/globules (n = 147, 29%) and maple-leaf-like areas (n = 70, 13.8%). Superficial tumours exhibited mainly maple-leaf-like areas, spoke-wheel areas and brown dots, whereas pigmented nodular BCC was most frequently typified by the presence of blue-grey ovoid nests.

Dermoscopy allows detection of pigmentation in about 30% of clinically nonpigmented BCCs, providing additional information that may aid the clinical choice of adequate treatment modalities.