Introduction to reflectance confocal microscopy and its use in clinical practice

Abstract

Reflectance confocal microscopy (RCM) is a novel technology that provides noninvasive, in vivo imaging of the skin at nearly histologic resolution. In 2016, the US Centers for Medicare and Medicaid Services (CMS) established reimbursement codes for RCM image acquisition and for the reading and interpretation of images. The combination of RCM imaging with dermoscopy has improved the accuracy of skin cancer diagnosis while reducing the number of biopsies of benign skin lesions. With that, we are starting to see more dermatologists and dermatopathologists using RCM in clinical practice. This editorial is to serve as an introduction on RCM imaging with a focus on its usefulness in both the diagnosis and management of skin cancers. We end by briefly describing the characteristic RCM features of normal skin to serve as a building block for later cases that will explore both the benefits and drawbacks of incorporating RCM imaging for benign and malignant lesions.

Keywords: CMS, US Centers for Medicare and Medicaid Services; CPT, current procedural terminology; LM, lentigo maligna; NNT, number needed to treat; RCM, reflectance confocal microscopy; innovative technology; lentigo maligna; melanoma; noninvasive imaging; nonmelanoma skin cancer; reflectance confocal microscopy; skin cancer.

Fig 1

A, RCM image (0.5 × 0.5 mm) of stratum corneum in normal skin. Dark linear furrows (blue star) represent dermatoglyphs (skin folds). B, Close up of anucleated corneocytes in the stratum corneum. A high-resolution version of this slide for use with the Virtual Microscope is available as eSlide:VM05397.

Fig 2

A, RCM image (0.5 × 0.5 mm) of normal honeycomb pattern at the stratum granulosum–spinosum level. B, RCM image (0.5 × 0.5 mm) of a broadened honeycomb pattern at the stratum granulosum–spinosum level. C and D, RCM image (0.5 × 0.5 mm) of an irregular honeycomb pattern as displayed by a disruption of the honeycomb pattern with cells of variable size, shape and contour thickness. A high-resolution version of this slide for use with the Virtual Microscope is available as eSlide:VM05398. A high-resolution version of this slide for use with the Virtual Microscope is available as eSlide:VM05400. A high-resolution version of this slide for use with the Virtual Microscope is available as eSlide:VM05399.

Fig 3

Disarranged pattern in a biopsy-proven melanoma displays a disarray of normal architecture of the superficial layers with unevenly distributed bright granular particles and cells, in the absence of honeycombed or cobblestone. This pattern is more frequently observed in invasive melanomas, usually associated with pagetoid cells although can be seen in other skin malignancies. A high-resolution version of this slide for use with the Virtual Microscope is available as eSlide:VM05401.

Fig 4

RCM image (0.5 × 0.5 mm) of bright cells in pagetoid spread and dendritic cells extending down the follicular infundibulum in a biopsy-proven lentigo maligna. A high-resolution version of this slide for use with the Virtual Microscope is available as eSlide:VM05407.

Fig 5

Pigmented basal keratinocytes at the suprabasilar layer displaying a cobblestone pattern owing to the high refractive index of their supranuclear melanin caps. A high-resolution version of this slide for use with the Virtual Microscope is available as eSlide:VM05402. A high-resolution version of this slide for use with the Virtual Microscope is available as eSlide:VM05403.

Fig 6

A, RCM image (0.5 × 0.5 mm) of dermal papillae surrounded by bright basal keratinocytes and melanocytes (edged papillae) at the DEJ. B, RCM mosaic (1.0 × 1.0 mm) of papillary contours that are not well outlined (nonedged) in a melanoma in situ. A high-resolution version of this slide for use with the Virtual Microscope is available as eSlide:VM05404. A high-resolution version of this slide for use with the Virtual Microscope is available as eSlide:VM05405.

Fig 7

RCM mosaic of the superficial dermis, which appears less refractile and contains dark tubular or canalicular blood vessels and bright collagen fibers. A high-resolution version of this slide for use with the Virtual Microscope is available as eSlide:VM05406.