American Board of Internal Medicine (ABIM) Certification Practice Exam

For patients with melanomas of 1- to 4-mm thickness, what is the next best clinical step?

1. Observation

2. Sentinel lymph node biopsy

3. Chemotherapy

4. Topical immunotherapy

The correct answer is: Sentinel lymph node biopsy

For patients with melanomas that measure between 1 and 4 mm in thickness, the recommended next best clinical step is a sentinel lymph node biopsy. This procedure is crucial for staging and determining the prognosis of melanoma. When the melanoma is between 1 to 4 mm thick, there is a significant risk of lymphatic spread. The sentinel lymph node biopsy allows for the assessment of the first lymph node(s) that would typically receive drainage from the melanoma site. If these nodes contain cancer cells, it may indicate that the melanoma has started to spread, which would influence subsequent treatment options and the overall management of the disease. Choosing observation alone would not provide necessary information about potential metastasis, which is critical in treatment planning. Likewise, the use of chemotherapy at this stage is generally not indicated, as systemic therapy is not a primary treatment for localized melanoma. Topical immunotherapy is also not appropriate for tumors of this thickness, as it is typically used for superficial skin lesions or in specific cases where the melanoma is in situ or very thin. Overall, sentinel lymph node biopsy is an essential step in managing melanomas of this thickness to guide further treatment decisions based on the staging results.