Can Fine Needle Aspiration Cytology (FNAc) be performed on a swelling with active infection or inflammation?

Fine Needle Aspiration Cytology in Active Infection or Inflammation

Fine needle aspiration cytology (FNAC) should generally be avoided in areas with active infection or inflammation as it may spread the infection, worsen inflammation, or yield non-diagnostic samples.

Rationale for Avoiding FNAC in Active Infection

The American College of Radiology (ACR) guidelines provide important insights regarding the management of infectious and inflammatory conditions:

• In cases of suspected infection, aspiration is primarily recommended for diagnostic confirmation of septic arthritis or for therapeutic drainage of abscesses, not for routine cytological evaluation 1
• When infection is suspected, the ACR recommends imaging studies (particularly MRI or CT) as the initial approach rather than immediate tissue sampling 1
• For soft tissue infections, the diagnostic pathway typically involves imaging first to characterize the extent and nature of the infection before considering invasive procedures 1

Risks of FNAC in Active Infection

Performing FNAC in areas of active infection carries several significant risks:

1. Spread of infection - Needle passage through infected tissue may disseminate bacteria to adjacent tissues or bloodstream
2. Worsening of inflammation - The mechanical trauma of needle insertion can exacerbate existing inflammation
3. Non-diagnostic samples - Inflammatory cells may overwhelm the specimen, making cytological diagnosis difficult or impossible
4. Delayed appropriate treatment - Reliance on FNAC may delay more appropriate interventions like antibiotic therapy or surgical drainage

Alternative Approaches

Initial Imaging Assessment

For swellings with suspected infection or inflammation, the following approach is recommended:

• CT scan with contrast is rated as "usually appropriate" (rating 7-9) for evaluation of soft tissue infections and extent of disease 1
• MRI with and without contrast is highly recommended (rating 9) for suspected osteomyelitis or soft tissue infection 1
• Ultrasound can be useful for follow-up of superficial lesions but is less valuable for initial assessment 2

Management Strategy

1. Control infection first - Treat with appropriate antibiotics before considering diagnostic sampling
2. Imaging-guided drainage - For abscesses, therapeutic drainage with culture is preferred over diagnostic FNAC
3. Wait for resolution - Perform FNAC only after acute infection/inflammation has resolved if a mass persists

Exceptions and Special Considerations

There are limited circumstances where FNAC might be considered despite active infection:

• When malignancy is strongly suspected and needs to be ruled out urgently
• For identification of specific pathogens when other diagnostic methods have failed 3
• For deep-seated lesions where surgical biopsy carries higher risks than FNAC

In these exceptional cases, the procedure should be performed with:

• Antibiotic prophylaxis
• Careful technique to minimize tissue trauma
• Immediate processing for microbiological studies

Evidence from Case Reports

While generally not recommended, there are isolated reports of successful use of FNAC in infectious settings:

• A case of Candida albicans infection masquerading as a soft tissue tumor was diagnosed by FNAC, but this was an unusual presentation rather than a clearly infected site 3
• Some studies report FNAC being useful in diagnosing specific infections like actinomycosis, but these typically involve chronic rather than acute infections 4

These exceptions should not override the general principle of avoiding FNAC in actively infected or inflamed tissues until the acute process has resolved.