Reflectance Confocal Microscopy Characteristics
Reflectance confocal microscopy (RCM) images show a well-defined, hyper-refractile lesion at the center of the image (Figure 2 ). Honeycomb pattern and small bright cells and large bright dendritic cells can be seen in the epidermis. Edged papillae at the level of the dermal epidermal junction can be seen surrounding a central, homogeneous area. A lobule of polygonal, interconnected cells, likely epithelial cells distinct from surrounding keratinocytes, can be seen in the dermis at the inferior margin of the lesion. Superior margin shows polycyclic rings representing dermal epidermal junction, surrounding and overlying a homogenous refractile area (Figure 2C ). The RCM features are suggestive of a metastatic tumor, as it lacks features of a squamous cell carcinoma, basal cell carcinoma, melanocytic tumor and other epithelial infiltrates. Other epithelial infiltrates such as sarcoidosis, foreign body granulomas and lymphomas can also be excluded. For example, sarcoidosis will have large macrophages which will be visualized under RCM which this case lacks. Foreign body granuloma can be excluded as there is no evidence of foamy/multinucleated giant cells surrounded by fibrous response. Lymphoma can be excluded as there is no evidence of lymphocytes that are visible as hyperreflective bright cells with high density.