Clinic & Revision




Clinicians in the UK generally follow guidelines described in a consensus document produced in 2007 by the Royal College of Pathologists with the British Thyroid Association.


Thy 1
Definition: non diagnostic for cytological diagnosis. A Thy 1 alone is non diagnostic due to inadequate sample. An adequate sample from a solid lesion should have at least six groups of thyroid follicular epithelial cells across all the submitted slides, 
each with at least 10 well-visualised epithelial cells. 
Management: repeat FNAC


Thy 1c
Definition: non diagnostic due to the cystic nature of the lesion itself. Malignancy subsequently found in 4-8%
Management: repeat FNAC


Thy 2
Definition: non- neoplastic
Management: repeat US FNA in 3-6 months to exclude neoplasia. If symptomatic of high risk consider diagnostic hemithyroidectomy


Thy 3
Definition: neoplasm possible (10-40%)
Management: depends if Thy 3a or 3f


Thy 3a
Definition: cellular atypia but not enough to put into other categories
Management: depends on size but most get diagnostic hemithyroidectomy. Some argue a repeat FNA


Thy 3f
Definition: follicular neoplasm suspected (but you cannot say from an FNA if benign or neoplastic)
Management: diagnostic hemithyroidectomy


Thy 4
Definition: highly suspicious of malignancy (70-90% chance) but not definite. Usually papillary carcinoma but can be medullary, anaplastic carcinoma, or lymphoma.
Management: diagnostic hemithyroidectomy. Wait for histology and then decide if need CT


Thy 5
Definition: diagnostic of malignancy (although in reality 99% value more true). Can be any type (papillary, medullary, anaplastic, lymphoma, metastatic)
Management: total thyroidectomy and if CT shows metastases then get radioiodine. Radiotherapy and/or chemotherapy is indicated for anaplastic thyroid carcinoma, lymphoma or metastatic tumour.


Author: Johno Breeze

Last updated: 16/02/15