Expansion
More tissue gives more information but carries more risk
Expansion
| Technique | Yields | Best for | Limits |
|---|---|---|---|
| Fine needle aspiration | Cells only (cytology) | Thyroid nodules, cysts, lymph node staging, salivary gland | No architecture, so cannot grade or subtype; higher inadequate rate |
| Core biopsy | Tissue core with architecture | Breast, prostate, liver, kidney, most solid masses | Sampling error; bleeding risk |
| Incisional biopsy | Part of the lesion | Large or fixed lesions | Leaves disease behind |
| Excision biopsy | Whole lesion | Lymphoma, melanoma, small lesions | More invasive; may compromise later surgery |
| Punch biopsy | Full thickness skin | Rashes, skin lesions | Small sample |
The governing principle: cytology answers “are these cells malignant”; histology answers “what is it, what grade, has it invaded, and what are the receptors”. The more the management depends on subtype and receptor status, the more tissue is needed.
Specific rules worth knowing
- Lymphoma: excision or generous core, never fine needle alone, since classification depends on nodal architecture and immunophenotype
- Melanoma: excision with a narrow margin, not shave or punch, because Breslow thickness determines staging and treatment
- Sarcoma: biopsy must be planned by the operating surgeon, along the line of the future incision, since a badly placed tract contaminates tissue planes and can cost the limb
- Breast: triple assessment, being clinical, imaging and pathological, with core biopsy for receptor status
- Prostate: transperineal biopsy, now usually preceded by MRI
Before any biopsy: clotting and platelets, anticoagulant and antiplatelet status, consent including bleeding, infection, pneumothorax and seeding, and correct labelling with the site, since specimen mix-ups have led to unnecessary mastectomies.