Excisional and Incisional Biopsy
Excisional biopsy removes the whole lesion, with a rim of normal tissue where possible, for diagnosis and often for cure. Incisional biopsy removes a representative wedge or ellipse from a larger lesion, leaving the rest for definitive treatment after the diagnosis is known.
Both give the pathologist a large piece of tissue, with the architecture, the margins and the depth of the lesion. They are the usual choice when a needle sample is likely to be non-diagnostic or misleading.
Excision suits lesions small enough to remove completely: suspected melanoma, a skin tumour, a lymph node, a breast lump, or a small soft tissue mass. Incisional biopsy is used for large tumours, lesions in sites where excision would cause loss of function or deformity, and suspected soft tissue or bone sarcoma.
The procedure is done in an operating room or minor procedure room under local, regional or general anaesthesia. It takes 15 to 60 minutes, and the result is usually available in 3 to 7 days.
A definitive diagnosis is reached in most cases. The most important determinants of an accurate result are a representative sample, correct handling, and orientation of the specimen.
Indications.
- A lesion of uncertain nature that is small enough for complete removal.
- Suspected melanoma (excision with a narrow margin).
- Enlarged lymph node of unknown cause, especially suspected lymphoma, where a whole node gives the best material.
- Lumps in the breast and soft tissues when a needle sample is inconclusive.
- Extensive or deep inflammatory skin disease and panniculitis.
- Large tumours needing a diagnosis before planning of treatment (incisional).
- Suspected sarcoma after imaging (incisional, planned with the surgeon who will do the final operation).
- Non-diagnostic or discordant core or aspirate result.
Not indicated as the first step for a deep or large soft tissue mass before imaging, because a badly planned incision can contaminate tissue planes and limit later surgery.
Contraindications and precautions.
- Bleeding disorder, or anticoagulant treatment that has not been managed.
- Active infection at the site.
- Lesion close to major nerves, vessels or functional structures.
- For a suspected soft tissue sarcoma (a mass over 5 cm, deep to the fascia, or growing), imaging first and sampling in a sarcoma service where possible, with the incision placed along the line of later resection.
- For a suspected melanoma, wide excision is avoided before diagnosis, and a shave or partial sample is avoided because depth is measured from an intact specimen.
- Cosmetically and functionally critical sites (face, hand, genitalia) need planning.
- Poor wound healing: diabetes, smoking, vascular disease, immunosuppression and steroid use.
Preparation and technique.
Consent is taken, the lesion is marked, measured and photographed, and any prior imaging is reviewed. A plan for specimen orientation and for how the wound will be closed is made.
Local anaesthetic (lidocaine, with adrenaline in most sites but not in the fingers, toes, nose, ear or penis) is infiltrated around the lesion. The skin is cleaned and draped.
For skin lesions, an ellipse with a length three times the width is marked along the relaxed skin tension lines, which allows closure without a dog ear. The incision goes through the full thickness of the skin to the subcutaneous fat or deeper, as the lesion requires. For melanoma, the deep margin is taken to the fascia without breaching it.
For an incisional biopsy, a wedge or ellipse of tissue is taken from the edge of the lesion, including normal tissue, and avoiding necrotic centres. Areas near neurovascular structures are avoided.
The specimen is oriented with a suture or ink at a marked point (usually 12 o'clock), placed in formalin without delay and sent with a diagram and clinical details. Fresh tissue is sent in saline for lymph node excision when lymphoma is suspected, for flow cytometry, and a part is sent for culture. Haemostasis is achieved, and the wound is closed in layers.
