Reflectance confocal microscopy (RCM) is a non-invasive device that images skin lesions in vivo at a cellular resolution to guide management of patient care. While previous studies have demonstrated high accuracy of RCM in diagnosing skin cancers, most of these studies were performed by experts as a blinded analysis off-site and does not reflect true clinical scenario. We assessed the diagnostic potential of a novice RCM reader, in clinical settings, at the bedside. Over a period of 15 months (August 2015- November 2016), 168 lesions (from 128 cases) were imaged with RCM to determine BCC and or melanoma in dermoscopically equivocal lesions. To evaluate the learning curve of the novice reader, diagnostic accuracy was evaluated at the end of 15 months, as well as during the first half (8 months) and latter half (seven months) of the study. Histopathological diagnosis was available in 95/168 lesions, including 38 melanocytic lesions (ML: 13 melanomas and 25 nevi) and 57 non-melanocytic lesions (NML: 26 BCCs, 4 SCCs and 27 benign). The remaining 73/168 lesions (43.45%) were not biopsied (received topical treatment, monitoring). On RCM, 22/26 (84.61%) BCCs and 11/13 (84.61%) melanomas were correctly diagnosed. BCC was missed in 3/26 (11.53%) lesions and melanoma in 2/13 (15.38%) lesions; these lesions were diagnosed mostly as superficial BCCs and focal epidermal changes overlying deeply situated melanoma nodule on histopathology, respectively. False positive diagnosis of BCC was obtained in 6/52 (11.54%) benign lesions and of melanoma in 2/52 (3.85%) lesions; these were diagnosed mostly as benign inflamed keratosis and moderately atypical dysplastic nevus on histopathology, respectively. In 6 lesions BCC or melanoma could not be ruled out. An increase in the sensitivity and specificity was noticed between the two halves of the study. A high sensitivity and specificity of 83.33% and 76.60%, respectively in diagnosing skin cancers was obtained. Based on this study, we identified some current limitations and potential pitfalls of RCM. The fact that the diagnostic accuracy of the novice reader increased with time, indicates a learning curve reading RCM images. Additionally, current technical limitations of RCM such as inability to differentiate various cell types, sampling error, and, shallow depth of imaging also lead to false diagnosis. Efforts are ongoing to overcome these challenges by building US based teachingtraining program and through a multimodal imaging approach for better diagnosis and patient care.

Date Published: 24 March 2017
PDF: 18 pages
Proc. SPIE 10060, Optical Biopsy XV: Toward Real-Time Spectroscopic Imaging and Diagnosis, 1006002 (24 March 2017); doi: 10.1117/12.2255685

Published in SPIE Proceedings Vol. 10060:
Optical Biopsy XV: Toward Real-Time Spectroscopic Imaging and Diagnosis
Robert R. Alfano; Stavros G. Demos, Editor(s)