From the Guidelines
To diagnose a skin lesion, an excisional biopsy is the most definitive lab test, involving the removal of the entire lesion with a narrow peripheral margin of 1 to 3 mm around the concerning skin lesion, as recommended by the most recent guidelines 1. This procedure is typically performed under local anesthesia and involves removing the entire lesion with a scalpel, which is then sent to a pathology lab for examination. The choice of biopsy type depends on the lesion's characteristics and suspected diagnosis. Some key points to consider when performing a skin biopsy include:
- The use of dermoscopy to improve diagnostic accuracy and direct optimal tissue sampling 1
- The importance of prebiopsy photographs to aid in clinical/pathologic correlation and prevent wrong-site surgery 1
- The need for a narrow peripheral margin of 1 to 3 mm around the concerning skin lesion to ensure accurate staging and treatment planning 1 Other helpful tests may include:
- Dermoscopy (examining the lesion with a special magnifying device)
- Wood's lamp examination (using ultraviolet light to detect certain conditions)
- Molecular testing for genetic markers (in some cases) These tests help differentiate between benign conditions, infections, inflammatory disorders, and skin cancers, guiding appropriate treatment decisions. It's worth noting that the most recent guidelines from the Journal of the American Academy of Dermatology 1 provide the most up-to-date recommendations for the diagnosis and management of primary cutaneous melanoma, and should be consulted for further information.
From the Research
Diagnostic Laboratory Tests for Skin Lesions
The diagnostic laboratory test for a skin lesion is a skin biopsy, which involves removing a sample of skin tissue for examination under a microscope 2, 3, 4, 5.
Types of Biopsy Techniques
There are several types of biopsy techniques that can be used to diagnose skin lesions, including:
- Shave biopsy: used to remove a small sample of skin tissue from the surface of the skin 2, 4
- Punch biopsy: used to remove a small sample of skin tissue from the deeper layers of the skin 2, 4
- Excisional/incisional biopsy: used to remove a larger sample of skin tissue, often used to diagnose skin cancer 2
- Saucerization biopsy: used to remove a sample of skin tissue from a larger lesion 4
- Fusiform biopsy: used to remove a sample of skin tissue from a long, narrow lesion 4
- Subcutaneous nodule biopsy: used to remove a sample of skin tissue from a nodule located under the skin 4
Importance of Biopsy in Diagnosing Skin Lesions
Biopsy is an important diagnostic tool for skin lesions, as it allows for the examination of skin tissue under a microscope to determine the presence of disease or infection 3, 5, 6.
Additional Diagnostic Tests
In addition to biopsy, other diagnostic tests such as microscopy and culture may be used to diagnose fungal infections of the skin 6. Histopathological examination of a tissue biopsy can provide valuable diagnostic information, especially in cases where culture results are pending or inconclusive 6.