Infiltrating basal cell carcinoma: a stellate peri-tumor dermatoscopy pattern as a clue to diagnosis

Background: Infiltrating basal cell carcinoma (BCC) has associated features that may be readily identified using dermatoscopy.  Objective: Investigate a stellate dermatoscopy pattern extending from the peripheral margin of infiltrating BCC. Methods: A total of 741 consecutive cases of BCC were assessed retrospectively using non-polarized dermatoscopy. Following histopathologic examination, cases were categorized into six different BCC subtypes. Infiltrating cases numbered 107. This stellate feature was defined as a geometric star shaped pattern extending outwards from the circumferential peripheral edge of the tumor, and identified by white lines, vessels or uneven skin surface morphology. The percentages of infiltrating subtype within the tumor mass and tumor depth were compared, with and without the stellate pattern. Results: Infiltrating BCC displayed the stellate pattern more than other BCC subtypes. Concordance between the two observers was almost perfect for white lines: Kappa coefficient of 0.87 (95% CI: 0.0.79-0.95) P<0.01 and substantial for vessels: Kappa coefficient of 0.71 95% CI: 0.59-0.84) P<0.01. Folds were only recorded in infiltrating cases (n=3). Compared to other BCC subtypes the stellate pattern had a sensitivity of 31.7% and specificity of 94.1%. A higher mean fraction of the tumor mass containing infiltrating subtype was found when comparing stellate pattern observed to stellate pattern not observed (P<0.01). No statistically significant association was found between the tumor depth with and without the stellate pattern. Conclusion: This study found a higher incidence of the stellate pattern within infiltrating BCC compared to the other BCC subtypes. As the percentage of the infiltrating subtype within the tumors increased the incidence of the stellate pattern also increased.