Dermoscopic Features of Basal Cell Carcinoma on the Lower Limbs: A Chameleon!

BACKGROUND: Lower limbs represent an uncommon location for basal cell carcinoma (BCC) and only few reports have described dermoscopic features of BCC in this body site. Since BCCs of the lower limbs frequently display nonclassic BCC dermoscopic criteria, they can simulate other benign or malignant lesions.

OBJECTIVE: Our aim was to describe the dermoscopic features of BCC located on lower limbs and to define which criteria were more associated with their benign- or malignant-looking appearance.

METHODS: We conducted a retrospective study enrolling consecutive patients with histologically confirmed BCCs of the lower limbs. Lesions were classified in 7 categories according to the clinical and dermoscopic global appearance. Clear BCC, squamous cell carcinoma (SCC) or Bowen disease-like, Kaposi disease-like, melanoma-like, and aspecific pattern were considered malignant-looking lesions; however, seborrheic keratosis-like and dermatofibroma-like were considered benign-looking. To define which dermoscopic criteria were independently associated with benign- or malignant-looking appearance, we conducted a multivariate logistic regression analysis.

RESULTS: A total of 81 BCCs were enrolled: 18 (22%) were benign-looking lesions (of which 11 were seborrheic keratosis-like and 7 dermatofibroma-like) and 63 (78%) were malignant-looking BCCs (of which 24 were clear-cut BCCs, 23 SCC-like, 2 Kaposi disease-like, 9 melanoma-like, and 5 had aspecific pattern). Multivariate regression analysis showed that erosions/ulceration and vessels were independently associated with malignant-looking appearance. The most represented vessels were glomerular and polymorphic, which are more frequently encountered in SCC, together with ulceration.

CONCLUSION: BCC of the lower legs frequently simulates other benign or malignant lesions, with SCC being the main differential diagnosis.