In this technique, a thin (23–25 gauge (0.52 to 0.64 mm outer diameter)), hollow needle is inserted into the mass for sampling of cells that, after being stained, are examined under a microscope (biopsy).

[2] Aspiration is safer and far less traumatic than an open biopsy; complications beyond bruising and soreness are rare.

The skin above the area to be biopsied is swabbed with an antiseptic solution and draped with sterile surgical towels.

The skin, underlying fat, and muscle may be numbed with a local anesthetic, although this is often not necessary with superficial masses.

There are many reasons for this: After the needles are placed into the mass, cells are withdrawn by aspiration with a syringe and spread on a glass slide.

Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is a minimally invasive procedure for acquiring biopsies in gastric regions that are hard to reach otherwise (e.g. the pancreas).

[8][9][10][11] Rapid on-site evaluation (ROSE) is a real-time service during EUS-FNA interventions, that assesses the adequacy of the collected biopsy samples for diagnostics.

[12] ROSE is typically performed in the operating room and starts by transferring an aliquot of the FNA sample onto a glass slide.

Finally, a morphological assessment of the stained cells under a microscope allows us to evaluate the adequacy of the collected FNA sample.

If a lung or kidney biopsy has been performed, it is very common to see a small amount of blood in sputum or urine after the procedure.