OncologyTier 2Topic

Fine needle aspiration and excisional biopsy

The options

Fine needle aspiration (FNA) and excisional biopsy represent opposite ends of the tissue-sampling invasiveness spectrum - the choice depends on what diagnostic question needs answering and how much tissue architecture is required
FNA is typically the first-line, least invasive test for an accessible mass (thyroid nodule, palpable lymph node, breast lump); excisional biopsy is reserved for when architecture is essential or FNA is non-diagnostic

FNA - aspirates individual cells via a fine needle - provides cytological information (cell appearance) but not tissue architecture - cannot reliably distinguish carcinoma in situ from invasive carcinoma, or definitively subtype lymphoma
Core needle biopsy - an intermediate option, provides a tissue core preserving some architecture, often sufficient for diagnosis and increasingly preferred over FNA for many indications
Excisional biopsy - removes the entire lesion, providing full architecture, margin assessment, and (if malignant) can be simultaneously therapeutic

FNA is excellent for thyroid nodules (Bethesda classification system) and accessible lymph nodes, but generally inadequate alone for suspected lymphoma - architecture is needed for accurate lymphoma subtyping, so excisional (or at minimum core) biopsy is preferred when lymphoma is the leading differential
A non-diagnostic or discordant FNA result (e.g. benign cytology in a lesion with high clinical/radiological suspicion of malignancy) should prompt escalation to core or excisional biopsy, not reassurance

Excisional biopsy of a small lesion can be diagnostic and therapeutic simultaneously if performed with adequate margins - relevant to planning the initial biopsy approach for a lesion where complete excision might be curative

Thyroid nodules, lymphadenopathy/suspected lymphoma, breast lesions, soft tissue masses

Choosing the wrong initial biopsy technique (e.g. FNA alone for suspected lymphoma) can delay diagnosis and require a repeat procedure - matching the technique to the differential diagnosis at the outset avoids this

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