The diagnosis of MCC is made with a skin biopsy, which is examined under the microscope. Special stains are used to distinguish MCC from other forms of cancer, such as small cell lung cancer (SCLC), lymphoma, and small cell melanoma. Each of these cancers has a unique profile as defined by special stains (see table below). MCC will stain for low molecular weight cytokeratins (CAM 5.2 or AE1/AE3), CK 20 and neuron-specific enolase (NSE) (see photographs below). MCC will not stain for CK7 or thyroid transcription factor 1 (TTF-1) (positive in SCLC), leukocyte common antigen (LCA) (positive in lymphoma) and S100 (positive in small cell melanoma).