Shave Biopsy
Shave biopsy removes a thin layer of epidermis and upper dermis with a blade held nearly parallel to the skin. It is fast, needs no suture, and leaves a shallow wound that heals by secondary intention. Variants are the superficial shave (epidermis and papillary dermis), the saucerization shave (a deeper, concave section into the mid-dermis), and the scoop or curette biopsy.
It is used for raised and exophytic lesions and for superficial skin disease. It is poor for lesions where depth matters, because the base is often cut across, and the deeper dermis and fat are not sampled.
The procedure takes under 10 minutes under local anaesthesia. The specimen is a flat disc or curl of tissue with a width of 3 to 15 mm.
Most shave biopsies of benign and superficial malignant lesions give a clear diagnosis. The main risk is under assessment of depth in lesions that are thick or deep.
Indications.
- Raised benign lesions: seborrhoeic keratosis, skin tags, warts, dermatofibroma (superficial).
- Actinic keratosis, Bowen disease and superficial keratinocyte carcinomas (basal cell carcinoma, squamous cell carcinoma).
- Lesions of uncertain nature that are exophytic and probably benign.
- Superficial inflammatory conditions and scaly eruptions where only the upper skin is needed.
- Diagnostic sampling in places where a punch or excision is difficult, such as the face.
- Removal of benign lesions for cosmetic reasons, with the specimen sent for histology.
Not indicated for pigmented lesions suspected to be melanoma, for panniculitis, vasculitis, deep fungal infection, and for lesions where depth must be measured.
Contraindications and precautions.
- Suspected melanoma: shave biopsy cuts across the base and can underestimate depth. If a shave has already been done and shows melanoma, the deep margin status is reported and the thickness is interpreted with caution.
- Bleeding disorder, infection at the site, and allergy to local anaesthetic.
- Lesions of the eyelid and lip need care.
- Deep or large lesions, nodular basal cell carcinoma subtypes that infiltrate (morphoeic), and recurrent tumours need a deeper sample.
- Keloid tendency and darker skin: risk of pigment change and scarring.
- Anticoagulants usually continue.
Preparation and technique.
The lesion is examined, measured and photographed, and dermoscopy is used to exclude a melanocytic lesion.
The skin is cleaned and local anaesthetic (lidocaine) is injected under the lesion to raise it. The raised area allows a flat cut. A flexible blade, a scalpel or a razor blade is held almost parallel to the surface and used with a smooth, sawing motion to remove the lesion at its base.
The depth is chosen to include the full thickness of the abnormal tissue. In a saucerization, the cut is a curved, shallow dish that goes beyond the edges of the lesion.
Bleeding is controlled with pressure, an astringent such as aluminium chloride or ferric subsulphate, or light electrocautery. The base is not cauterised more than necessary, to avoid artefact in the specimen. The specimen goes into formalin, and a dressing with petrolatum is applied.
