Thyroid FNA Cytology

What it does

Thyroid FNA Cytology reads a scanned thyroid fine-needle aspiration, either a direct smear or a liquid-based preparation. Fine-needle aspiration is the step after a suspicious nodule on ultrasound, and its category decides between follow-up, repeat aspiration, molecular testing and surgery.

The run assesses adequacy and assigns a category of The Bethesda System for Reporting Thyroid Cytopathology, 3rd edition (TBSRTC 2023), from I to VI. With the category it returns the risk of malignancy that TBSRTC 2023 associates with it and the usual management, so the result reads the way a cytology report is used at the endocrine clinic.

Intended use

Decision support for the cytopathologist, with most value in the indeterminate categories III (atypia of undetermined significance) and IV (follicular neoplasm), where reader agreement is lowest and the next step is least obvious. For these categories the guidance lists the options TBSRTC 2023 gives, such as repeat aspiration, molecular testing or diagnostic lobectomy, without choosing between them.

Who it is for

Cytopathologists, general pathologists who report thyroid FNA without subspecialty training, and endocrinologists or surgeons reviewing outside cytology. Developers use the run to close the loop between a thyroid ultrasound report and its cytology result in one data model.

Accepted input

• One FNA slide per run: a Papanicolaou- or Romanowsky-stained direct smear, or a liquid-based cytology slide, scanned as a whole-slide image.
• Formats: DICOM VL Whole Slide Microscopy Image, or the scanner's own file (SVS, NDPI, MRXS, iSyntax, SCN, BIF, CZI, OME-TIFF).

Requirements

Requirement	Why
Stain recorded with the slide	Pap and Romanowsky stains show nuclear and colloid features differently
Pixel spacing in µm/px	Nuclear size and follicular-group size are compared in micrometres
Focus through thick smear areas	Follicular groups and papillary fragments are three-dimensional

Optional context

The ultrasound finding (TI-RADS category, nodule size and location) and prior cytology can be passed in clinical_context, where they inform the management guidance.

The result

Section	Content
Bethesda category	Adequacy, TBSRTC 2023 category I–VI, the associated risk of malignancy and usual management
Draft report	Opt-in (options.report): an English narrative that interprets the result for the reader (findings, impression, limitations); every number is checked against the findings

Standards

• Reporting: The Bethesda System for Reporting Thyroid Cytopathology, 3rd edition, 2023 (TBSRTC 2023).
• DICOM: the category and adequacy in SR TID 1500 and the report as Encapsulated PDF.
• Interoperability: FHIR R4 DiagnosticReport with an Observation for the category.

TBSRTC 2023 categories

Category	Name
I	Nondiagnostic
II	Benign
III	Atypia of undetermined significance (AUS)
IV	Follicular neoplasm
V	Suspicious for malignancy
VI	Malignant

Works with

Thyroid Ultrasound (us/thyroid) grades the nodule with ACR TI-RADS and recommends aspiration; this model reads the resulting cytology, linking imaging risk to the cytology category for the same nodule.