Non-invasive characterization of different types of basal cell carcinomas (BCCs) using vibrational optical coherence tomography (VOCT): Can early lesions as small as 0.05 mm be identified by VOCT?

Abstract

Vibrational optical coherence tomography (VOCT) has been used to non-invasively measure the resonant frequency and elastic modulus of different types of BCCs to compare the physical biomarker characteristics of each of these lesions. The results suggest that in very small lesions (about 0.05 mm in diameter) new 80Hz and 130Hz resonant frequency peaks are seen not present in normal skin or in healing wounds. In all other BCCs, new 80Hz, 130Hz and 260Hz resonant frequency peaks are found like those found in other carcinomas including SCC and melanoma. Small BCCS are characterized by new 80Hz and 130Hz in the absence of a significant 50Hz peak unlike actinic keratoses that are characterized by 50Hz, 80Hz and 130Hz peaks. In the absence of the 260Hz peak, small BCCs appear to be a precursor to larger BCCs. Pigmented BCCs exhibit a larger ratio of the 50Hz/80Hz peaks compared to the other BCC types in addition to peaks at 130Hz and 260Hz suggesting that benign melanocyte lesions contribute to the 50 Hz peak. Further studies are needed to understand the factors that drive differences in shape and invasiveness of cancerous BCCs. While all BCCs were found to contain new cell and blood vessel resonant frequencies that coincide with fibrotic tissue encapsulating the tumors in the papillary dermis, other factors must drive differences in the shape and invasiveness of the different BCCs. It is hypothesized that the new cells and blood vessels formed lead to the deposition of fibrous tissue in all BCCs and is partially driven by an epithelial-mesenchyme transition. It is concluded that fibrotic tissue is found encapsulating all cancerous BCCs and that this layer of tissue may limit invasiveness and metastatic behavior of this tumor type. In general, tumor shape and invasiveness are likely influenced by the exact cellular mutations in each lesion type and the extent of UV light damage experienced by the surrounding extracellular matrix.