FNA Specimen Handling: Send to Pathology, Not Endocrinology
FNA biopsy specimens should be sent to the pathology laboratory for cytopathologic evaluation, not to an endocrinologist. The endocrinologist is the referring clinician who orders and may perform the FNA, but the specimen itself requires processing and interpretation by a cytopathologist 1, 2.
The Correct Workflow
Who Does What
- Endocrinologist's role: Performs or orders the FNA based on clinical and ultrasound findings, provides clinical context, and manages the patient based on cytology results 2
- Pathologist's role: Receives the specimen, processes it appropriately, performs microscopic evaluation, and issues the diagnostic cytopathology report 1
Critical Communication Requirements
You must send the FNA specimen to pathology with a detailed requisition form that includes 3:
- Patient identity, date of birth, relevant oncological history
- Nodule characteristics: size, location, EU-TIRADS score, evolution
- Thyroid function status and any thyroid medications
- Calcitonin level if medullary carcinoma suspected
- Number of passes performed and locations sampled
- Whether anticoagulants were held
Specimen Processing Details
What Gets Sent to Pathology
The pathology laboratory needs specific preparations depending on suspected diagnosis 1:
- Standard thyroid nodules: Air-dried smears (Diff-Quik) and alcohol-fixed smears (Papanicolaou staining)
- Suspected lymphoma: Material in tissue culture media (Roswell Park Memorial Institute medium) for flow cytometry
- Suspected infection: Additional material for culture
- Cell block preparation: For immunohistochemical studies when needed
Special Handling for Specific Scenarios
For suspicious lymph nodes 2:
- Send FNA specimen for cytology
- Request thyroglobulin or calcitonin measurement on FNA washout fluid
- Each center should establish its own reference ranges for washout measurements
For complex/cystic nodules 2:
- Submit both the FNA specimen from solid components AND the drained fluid for separate cytologic examination
Common Pitfalls to Avoid
Don't Skip the Clinical Information
Pathologists cannot provide optimal interpretation without clinical context 4, 5. A cytopathology report is only as good as the clinical information provided. Inadequate clinical data leads to vague morphologic descriptions rather than clinically actionable diagnoses 4.
Understand the Reporting System
The pathologist will report results using the Bethesda System (Categories I-VI) 6:
- Category I: Nondiagnostic
- Category II: Benign
- Category III: Atypia of undetermined significance (AUS/FLUS)
- Category IV: Follicular neoplasm
- Category V: Suspicious for malignancy
- Category VI: Malignant
The endocrinologist then uses this pathology report to guide clinical management 2, not the other way around.
When Onsite Cytopathology Matters
If available, onsite cytopathology evaluation during the FNA procedure significantly improves diagnostic yield (96.2% vs 78.2% sensitivity) and reduces inadequate samples (1% vs 12.6%) 7. However, this still means the pathologist comes to where the FNA is performed—the specimen doesn't go to the endocrinologist's office.
The Bottom Line
The specimen pathway is: Patient → FNA procedure → Pathology laboratory → Cytopathology report → Back to endocrinologist for clinical management. The endocrinologist never receives the raw specimen for interpretation—that's the pathologist's domain 1, 3.