melanomas are almost always invasive. Staging Further context on cancer staging is available at TNM. Metastatic melanomas can be detected by X-rays, CT scans, MRIs, PET and PET/CTs, ultrasound, LDH testing and photoacoustic detection. However, there is lack of evidence in the accuracy of staging of people with melanoma with various imaging methods. Melanoma stages according to AJCC, 8th edition: TX: Primary tumor thickness cannot be assessed (such as a diagnosis by curettage) T0: No evidence of primary tumor (such as unknown primary or completely regressed melanoma) Stage 1 and 2 require an N (lymph node) class of: N0 – No regional metastases. Stage 1, 2 and 3 require an M (metastasis status) of: M0: No evidence of distant metastasis Older systems include "Clark level" and "Breslow's depth", quantifying microscopic depth of tumor invasion. Laboratory Lactate dehydrogenase (LDH) tests are often used to screen for metastases, although many patients with metastases (even end-stage) have a normal LDH; extraordinarily high LDH often indicates the metastatic spread of the disease to the liver. It is common for patients diagnosed with melanoma to have chest X-rays and an LDH test, and in some cases CT, MRI, and/or PET scans. Although controversial, sentinel lymph node biopsies and examination of the lymph nodes are also performed in patients to assess spread to the lymph nodes. A diagnosis of melanoma is supported by the presence of the S-100 protein marker. HMB-45 is a monoclonal antibody that reacts against an antigen present in melanocytic tumors such as melanomas. It is used in anatomic pathology as a marker for such tumors. The antibody was generated to an extract of melanoma. It reacts positively against melanocytic tumors but not other tumors, thus demonstrating specificity and sensitivity. The antibody also reacts positively against junctional nevus cells but not intradermal nevi, and against fetal melanocytes but not normal adult melanocytes. HMB-45 is nonreactive with almost all non-melanoma human malignancies, with the exception of rare tumors showing evidence of melanogenesis (e.g., pigmented schwannoma, clear cell sarcoma) or tumors associated with tuberous sclerosis complex (angiomyolipoma and lymphangiomyoma). Prevention There is no evidence to support or refute adult population screening for malignant melanoma. Ultraviolet radiation Minimizing exposure to sources of ultraviolet radiation (the sun and sunbeds), following sun protection measures and wearing sun protective clothing (long-sleeved shirts, long trousers, and broad-brimmed hats) can offer protection. Using artificial light for tanning was once believed to