| Abstract: |
Imaging techniques capable of non-invasive, high-resolution, skin imaging in vivo have been the focus of recent attention in the dermatology field. These efforts are directed to improve the diagnostic accuracy of skin cancer, especially cutaneous melanoma. Reflectance-mode confocal microscopy (RCM) allows real time noninvasive histological imaging with cytological detail comparable to conventional histology of the skin when exploring cutaneous structures between the stratum corneum and the upper reticular dermis. RCM consists of a light source for illumination of a small spot within translucent tissue; and a point detector that detects back-scattered and reflected light though a pinhole. The pinhole prevents out-of-focus light from reaching the detector; as a result, only the optical plane in focus (confocal) is detected. Similar to dermoscopy images, real time images obtained by RCM are oriented horizontal to skin surface (optical transversal sections). Melanin provides strong contrast because of its high refractive index (1.7) relative to the surrounding epidermis; the melanosome size, similar to the near-infrared wavelengths (800-1064 nm), produces strong back scattering of the beam. Thus, cells containing melanin, such as pigmented keratinocytes, melanocytes, or melanophages, appear very bright when illuminated in this manner. Similarly, other organelles or cytoplasmic granules provide good contrast (albeit less intense than melanin), resulting in good imaging of cells containing them, such as Langerhans cells, lymphocytes, or cytoplasmic granules in keratinocytes at the stratum granulosum. Major confocal imaging criteria of pigmented lesions such as benign and malignant melanocytic tumors have been established. RCM imaging criteria of other skin cancers such as basal cell carcinoma, squamous cell carcinoma, oral cavity neoplasm, and mycosis fungoides have also been evaluated. RCM shows promise for: (1) guidance during biopsy collection; (2) monitoring histological architectural changes or dynamic process such as inflammatory response or capillary flow; (3) histological correlation with dermoscopic features; (4) monitoring of the response of a given lesion to treatment; and (5) demarcation of the extension of a lesion before proceeding to invasive treatments such as surgical excisions. The main limitation of RCM is its relatively low penetration through the dermis; currently, a maximum depth of 250-300 μm can be achieved, preventing imaging of structures located in deep dermis and hypodermis. The main challenge is the interpretation of images. Specific photographic atlas, courses and development of teledermatology may solve this problem. © Springer International Publishing AG, part of Springer Nature 2011, 2018. All rights are reserved. |
