Why the whole lesion is removed
A dark, irregular patch on the sole of the foot in a man with decades of outdoor work raises concern for melanoma. On the sole, this pattern is typical of acral lentiginous melanoma, the type not linked to sun exposure that is relatively more common in people with darker skin. For a suspected melanoma, the provider plans an excisional biopsy with narrow margins, removing the entire lesion. Removing the whole lesion allows the pathologist to measure its full thickness, the Breslow depth, which is the most important factor for staging and for planning further treatment.
Breslow depth and staging
The Breslow depth is the thickness of the tumor measured in millimeters from the top of the epidermis to the deepest tumor cell. Together with ulceration, it forms the core of the T category in melanoma staging and strongly predicts prognosis. A shave biopsy may cut through the base of the lesion, leaving the deepest part behind, so the true thickness cannot be measured and the tumor may be understaged. This is why excisional biopsy is preferred whenever a lesion is suspected to be melanoma.
| Statement | Assessment | Reason |
|---|
| It leaves a smaller scar | Wrong | An excision usually leaves a larger scar than a shave |
| It allows the full depth to be measured | Correct | Breslow depth guides staging and treatment |
| It keeps cancer from reaching lymph nodes | Wrong | A biopsy is diagnostic, not preventive |
| It removes all the cancer | Wrong | Wide local excision usually follows |
What happens after the biopsy
If melanoma is confirmed, the client usually needs a wide local excision with margins chosen according to the measured thickness, and some clients are offered sentinel lymph node biopsy based on the stage. The diagnostic excision uses narrow margins so that it does not disturb lymphatic drainage before staging. Saying the biopsy removes all the cancer, or that it prevents lymph node spread, overstates what a diagnostic procedure can do.
Watch out! Use the ABCDE features when teaching skin checks: Asymmetry, Border irregularity, Color variation, Diameter larger than 6 mm, and Evolution. Remind clients to check the soles, palms, and nail beds, where acral melanoma occurs.
Exam takeaway
Key point! For suspected melanoma, an excisional biopsy is done so the full Breslow depth can be measured; thickness drives staging and the width of later excision. A shave biopsy risks cutting through the base of the tumor.