From the Guidelines
Laboratory tests for malignant melanoma should include a skin biopsy, complete blood count (CBC), liver function tests (LFTs), lactate dehydrogenase (LDH) levels, and genetic testing for mutations in BRAF, NRAS, and KIT genes, with more extensive testing such as imaging studies and sentinel lymph node biopsy depending on the stage of the disease. The diagnosis of malignant melanoma typically starts with a skin biopsy, where pathologists examine tissue samples for cancerous cells and determine characteristics like Breslow thickness, ulceration, and mitotic rate 1. Blood tests such as CBC, LFTs, and LDH levels serve as important prognostic markers, with elevated LDH suggesting advanced disease 1. Genetic testing for mutations in BRAF, NRAS, and KIT genes helps guide targeted therapy decisions, as approximately 50% of melanomas have BRAF mutations that can be treated with specific inhibitors 1. Sentinel lymph node biopsy may be performed to check for cancer spread to nearby lymph nodes, especially in patients with stage III disease 1. For advanced cases, imaging studies like CT scans, MRI, PET scans, and occasionally brain MRI are used to detect metastases, with the specific tests ordered depending on the melanoma's stage and the presence of symptoms or signs of metastasis 1. During treatment, regular blood tests monitor therapy response and detect potential side effects, while tumor marker tests like S-100B protein may help track disease progression, although its use is not routinely recommended in the United States 1. It is essential to note that the extent of laboratory testing and imaging studies should be tailored to the individual patient's needs, taking into account the stage of the disease, the presence of symptoms, and the potential impact on treatment decisions 1.
From the Research
Lab Tests for Malignant Melanoma
The following lab tests are relevant for malignant melanoma:
- Serum lactate dehydrogenase (LDH) levels: Elevated postoperative serum LDH levels indicate the need for metastatic workup 2, 3, 4
- Blood tests: May be obtained at low cost and prove to be of benefit if metastases are identified, especially for patients with asymptomatic AJCC stage I or II disease 4
- Imaging studies:
- Chest roentgenograms (CXR): May be obtained at low cost and prove to be of benefit if metastases are identified, especially for patients with asymptomatic AJCC stage I or II disease 2, 4
- Computed tomographic (CT) scans: Of the thorax, abdomen, and pelvis, especially when the primary cutaneous site of the melanoma is below the waist, for detecting metastatic MM in patients with AJCC stage III disease 4
- Magnetic resonance imaging (MRI) scans: Of the brain, may be ordered based on symptoms or physical findings 4
- Radionuclide bone and liver scans: May be used to evaluate metastatic disease 2
- Radionuclide brain scan or computed tomography of the brain: May be used to evaluate metastatic disease 2
- Upper gastrointestinal tract series with small-bowel follow-through: May be used to evaluate metastatic disease, although the yield is low 2
Staging and Workup
The workup and staging of malignant melanoma focus on risk factors based on the visual aspects of a skin lesion, and staging is based on depth of invasion, mitotic rate, and spread into lymph nodes and other sites 5.