Biopsy and histologic evaluation have been the gold standard to diagnose skin tumors. Reflectance confocal microcopy (RCM) is a noninvasive, innovative diagnostic technique that enables visualization of different skin layers at an almost histologic resolution. RCM has been proven beneficial in management of various cutaneous lesions. This article highlights the clinical significance and future of RCM to diagnose common skin cancers. However, RCM cannot replace currently standard histopathologic diagnosis. More studies are required to better compare the sensitivity and specificity of skin cancer diagnosis using RCM.
Key points
- •
Reflectance confocal microcopy (RCM) is a noninvasive diagnostic technique that enables visualization of different skin layers at an almost histologic resolution.
- •
RCM shows distinct confocal features for different skin lesions, which allows benign skin lesions to be successfully differentiated from malignant lesions.
- •
With further studies and more widespread physician training in the technique, RCM has the potential to revolutionize the field of skin cancer tissue diagnosis.
Introduction
Until now, biopsy and histologic evaluation has been the gold standard to diagnose skin tumors. Reflectance confocal microcopy (RCM) is a noninvasive, innovative, and 21st century diagnostic technique that enables visualization of different skin layers at an almost histologic resolution. In the past decade RCM has been proven beneficial in management of various cutaneous lesions. The aim of this article is to highlight the clinical significance and future of RCM to diagnose common skin cancers. Confocal diagnostic features of benign melanocytic nevi, lentigo maligna, melanoma, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC) are discussed in this article.
Introduction
Until now, biopsy and histologic evaluation has been the gold standard to diagnose skin tumors. Reflectance confocal microcopy (RCM) is a noninvasive, innovative, and 21st century diagnostic technique that enables visualization of different skin layers at an almost histologic resolution. In the past decade RCM has been proven beneficial in management of various cutaneous lesions. The aim of this article is to highlight the clinical significance and future of RCM to diagnose common skin cancers. Confocal diagnostic features of benign melanocytic nevi, lentigo maligna, melanoma, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC) are discussed in this article.
Principle of reflectance confocal microcopy
The principle of RCM is based on focal point illumination and hence named confocal microscopy. The device uses a low power laser beam (infrared wavelength of 830 nm) to illuminate a small point inside the skin tissue. This light is reflected back through a small pinhole and is imaged on the detector. The pinhole aperture filters the scattered and reflected light and allows only the light from image plane to pass through it. In this way, the computer software produces a high-resolution, 2-dimensional, gray scale image of target lesion. Conventional RCM enables imaging depth up to 200 to 300 μm, which corresponds with the papillary dermis.
How to perform reflectance confocal microscopy
Fig. 1 displays a US Food and Drug Administration–approved clinical reflectance confocal microscope. Reflectance confocal microscopy is simple and quick procedure. Patient demographics with lesion history are entered into the computer software and the patient is prepared for confocal microscopy. A small drop of oil is applied to the target lesion and a metal ring with polymer or glass window is attached to the skin with the aid of an adhesive tape. A dermoscopy image is obtained with the vivacam through this metal ring. Next, ultrasound gel with a refractive index close to the epidermis is applied inside the metal ring. The metal ring is then connected magnetically with the vivascope head. RCM images composed of viva cubes and viva stacks are obtained at different skin layers including the epidermis, dermoepidermal junction, and upper dermis. These confocal images are stored and transferred through a high-speed Internet system to the clinical expert for analysis of the confocal images.
Reflectance confocal microcopy and skin cancer diagnosis
Nonmelanoma skin cancer, including SCC and BCC, constitutes the most common cancers in the United States. Melanoma skin cancer—although not the most common—has a notably higher mortality, rate causing more than 75% of all skin cancer deaths. However, early detection and better management can improve the prognosis of melanoma patients. With the aid of reflectance confocal microscopy, benign skin lesions can be differentiated successfully from malignant lesions. RCM shows distinct confocal features for different skin lesions. These confocal features aid in quick bedside diagnosis of melanoma and nonmelanoma skin cancers.
Melanocytic cancer diagnosis
To recognize confocal features of melanocytic cancer, we must first revise the features of benign melanocytic lesions such as benign melanocytic nevi ( Table 1 ). Benign melanocytic nevi has symmetric architecture, well-circumscribed regular honeycomb or cobblestone pattern of the epidermis, edged papillae, and homogenous dense and sparse dermal nests ( Fig. 2 )
| Type of Melanocytic Tumors | Characteristic Confocal Features |
|---|---|
| Benign melanocytic nevus | Symmetric architecture. Epidermis : Honeycomb or cobblestone pattern. DEJ : Regular ring pattern, edged or nonedged papillae. Dermis : Homogenous dense and sparse dermal nests. |
| Lentigo maligna | Epidermis : Disruption of the typical honeycomb or cobblestone pattern. Multiple large round pagetoid cells. DEJ : Disorganized architecture, nonedged papillae, atypical pleomorphic cells. Dermis : Large nucleated cells, plump bright cells |
| Malignant melanoma | Epidermis : Irregular honeycomb or cobblestone pattern, large nucleated pagetoid cells. DEJ : Disorganized ringed, meshwork, or unspecific pattern. Edged or nonedged papillae, uneven clusters and single atypical cells. Dermis : Dense and sparse nests of cells, plump bright and small bright cells, increased reticulated, curled and fragmented bright collagen fibers. |
Lentigo Maligna
It is difficult to differentiate clinically between lentigo simplex and lentigo maligna, which is the most common type of facial melanoma. RCM not only helps to make the right diagnosis, but also prevents the patients from having an unnecessary scar in case of a benign lesion on esthetically significant site. In the case of a large-sized lentigo, where a biopsy is taken from only a small area, a physician can miss a cancer diagnosis. RCM is beneficial in that the entire lesion may be imaged, enabling the physician to better diagnose a lesion.
Confocal features of lentigo maligna include disruption of the typical honeycomb or cobblestone pattern of the epidermis and the presence of multiple round pagetoid cells. The dermoepidermal junction shows a disorganized architecture and nonedged papillae. There are atypical pleomorphic cells defined as reflective cells with a size more than twice the diameter of keratinocytes. These cells have irregular shapes. Large nucleated cells may be seen within the dermal papillae.
Melanoma
Approximately 1.9% of men and women will be diagnosed with invasive melanoma at some point during their lifetime. The prognosis of melanoma depends largely on early diagnosis and timely management. RCM has revolutionized the management of melanoma by enabling physicians to make a quick bedside diagnosis. RCM features of melanoma have been well-studied and described in the last decade. Confocal features of melanoma includes irregular honeycomb or cobblestone pattern in the epidermis. The dermoepidermal junction shows complete architectural disarrangements with edged and nonedged papillae and cells with a size twice the size of keratinocytes ( Fig. 3 ). Large, round, nucleated cells with irregular shapes called pagetoid cells are also seen in melanomas.
Related posts:
Clinical Diagnosis of Skin Cancer
Enhancing Skin Cancer Diagnosis with Dermoscopy
Using Raman Spectroscopy to Detect and Diagnose Skin Cancer In Vivo
Proteomic Mass Spectrometry Imaging for Skin Cancer Diagnosis
Smartphone-Based Applications for Skin Monitoring and Melanoma Detection
Teledermatology Applications in Skin Cancer Diagnosis
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
