Dermoscopy and reflectance confocal microscopy-augmented characterization of pigmented micro-basal cell carcinoma (less than 2 mm diameter)

Background Basal cell carcinoma (BCC) is the most common skin cancer, accounting for approximately 80% of nonmelanoma skin cancer diagnoses each year. Among other factors, the staging of BCC is influenced by its measured diameter. Stage 1 BCC is defined as a lesion measuring 2 cm across or less. Of note, there have been increasing publications reporting features of "small-sized" BCCs, which can present smaller than 1 mm. However, few of these studies have characterized features of pigmented small-sized BCC. The application of in-vivo imaging such as dermoscopy and reflectance confocal microscopy (RCM) allows for the non-invasive distinction of these lesions from benign and malignant melanocytic neoplasms, thereby reducing unnecessary biopsies. Methods Within one year, three patients presented to Oregon Health and Science University's dermatology clinic with pigmented lesions of concern measuring less than 2 mm that were histologically confirmed as pigmented BCC. We sought to characterize the features of these lesions in a case series with the non-invasive imaging modalities of dermoscopy and RCM. Results All cases presented clinically as a small, brown, macule on the face. Each of the three cases exhibited differing features on dermoscopy. With the application of RCM, we were able to visualize characteristic BCC features, prompting removal by shave biopsy. Conclusion To our knowledge, no other study has reported dermoscopic and RCM features of a cohort of pigmented BCCs 2 mm in diameter or smaller. We propose to define BCCs of this size as micro-BCCs. The variability of dermoscopic findings observed in our study, combined with the small size of these pigmented lesions, shows the utility of RCM as a non-invasive diagnostic tool for pigmented micro-BCCs.