Minimally Invasive Follicular Carcinoma:
A Cytological and Histological Challenge
David Poller, Queen Alexandra Hospital,Portsmouth, UK
22 year old female euthyroid, T4 11.3 (N 7.0-20),
TSH 0.81 (N 0.35-5.0), Ab –ve
MNG, ultrasound guided FNA of a large 29mm solid
nodule in left lobe
Cytology
US guided FNA, 4 slides, air dried pap &
giemsa without rapid on site assessment
Moderate cellularity, virtually no colloid,
some cell clusters 3 dimensional with
some nuclear features suggestive of
papillary carcinoma; Thy4 ~Bethesda V,
Multidisciplinary team decision->left
thyroid lobectomy
Diagnosis
Thy4 = Bethesda Class V
suspicious neoplasm, cannot exclude FVPC
Left thyroid lobectomy = 20g
Minimally invasive well differentiated
follicular carcinoma, a 42mm pT3 well
differentiated follicular carcinoma, foci of
vascular invasion-> completion
thyroidectomy
Minimally Invasive Follicular Carcinoma
Requires assessment of whole lesion with capsule &
surrounding thyroid
WHO 2004 definition = transcapsular invasion or
vascular invasion
.
What is Invasion??
‘..Our review of the anatomy
of the thyroid gland confirms that this structure has
no defined anatomical
fibrous capsule..’
‘..We suggest that the
criteria for diagnosing
angioinvasion in thyroid
carcinomas as well as in
other endocrine tumors
are inconsistent. ..’
4000 carcinoma cases, very rigid criteria 118 cases
with tumour invading vessel wall & thrombus adherent
to intravascular tumour, 35% developed distant
metastases at mean 5.3y follow up
Minimal Invasion
‘..The importance of the study is
the confirmation that diagnostic
reproducibility of minimally
invasive FTC is low and that this
has clinical implications, and also
implications for the design of
studies into the treatment and
outcome of FTC’
Garcia-Rostan & Sobrinho-Simões Diagn Histopathol 2011; 17: 119.
Other Systems
Veracyte: Alexander et al NEJM 2012 mRNA needle washings, 265
nodules, high negative predictive value, 8% misclassified as benign,
BUT low +ve predictive value for malignancy, 48% of benign
nodules classified as suspicious, cost US$ 3200 per test
Assuragen miRInform: Braf, Ret/Ptc, Ras, Pax8/PPARg, specificity
98%, sensitivity 60% Hodak & Rosenthal Thyroid 2013, cost US
$650 per test
Finally
The criteria for maligancy in follicular lesions are not precise and
some follicular thyroid lesions with genotypes of follicular
carcinomas may well be ‘in situ’ lesions that do not demonstrate
invasion using conventional morphological criteria
If you want to diagnose thyroid nodules you need representative
cells from the lesion(s)
But in many cases Class I and Class III aspirate rates are high; eg
Class 1 up to 15%+ and Class III up to 20%, often because of poorly
prepared slides lacking cells
Rapid On Site Assessment is Essential