Thyroid ultrasounds of 150 patients with thyroiditis,
diagnosed by FNA,
were revised.
The following variables were described: the main sonographic patterns and the presence and location of perithyroidal lymph nodes.
- Ultrasound technique
The patients were examined in the supine position,
with the head in a medium extension,
and the base of the neck uncovered.
If hyperextension of the neck was required,
the patient was placed with a pillow underneath the shoulders.
To obtain a good resolution,
a high-frequency (10-15 MHz) linear transducer was used.
The thyroid was studied in B-mode and Color Doppler mode,
in at least two perpendicular planes (transverse and longitudinal) Fig. 4 .
In addition,
the central and lateral compartments were included to assess the presence of adenopathies,
as well as the dorsal and inferior area of the thyroid,
to look for parathyroid pathology.
Results
We observed and distinguished several sonographic appearances on patients with autoimmune thyroiditis:
- 4 main diffuse sonographic patterns [3,4]:
- Diffusely enlarged thyroid gland with hypoechoic parenchyma,
heterogeneous echotexture and often with lobular margins.
Fig. 5 This pattern is not only the most frequent,
but also,
it is associated with a greater lymphocyte infiltration of the gland,
lower levels of T4 and higher levels of anti-TPO antibodies.
- Geographic pseudonodular areas individualized by echogenic lines.
Fig. 6
- Micronodular pattern,
with the presence of numerous hypoechoic micronodules,
(1-7 mm),
with surrounding echogenic septations,
due to the fibrous septa that pass through the gland.
Fig. 7 It is also related to higher levels of anti-TPO antibodies.
- “Giraffe” pattern characterized by globular areas of hyperechogenicity surrounded by thin linear areas of hipoechogenicity.
Fig. 8
In the color Doppler study,
the thyroid parenchyma can show from mild to marked hypervascularization.
Fig. 9 This increase in vascularization is associated with the development of hypothyroidism.
In the end-stage may be a small and irregular gland with deformity of its contours that shows a more lobulated appearance and an increase in the diffuse heterogeneity due to fibrosis.
Fig. 10 In color Doppler,
vascularity decreases.
Fig. 11
- 3 focal sonographic patterns (less frequent):
- Hyperechogenic solid nodule with well-defined margins is the most frequent focal echographic pattern Fig. 12 . It appears with preserved echogenicity of the gland or with diffuse involvement.
Regarding the color Doppler study,
the vascularization is very variable Fig. 13 ,
without a typical pattern [5].
Practically in 100% of the cases in which we have characterized these nodules in our hospital with fine needle aspiration (FNA) procedure,
they have corresponded to an area of focal thyroiditis,
so they could be controlled by ultrasound [6].
- Area of pseudonodular appearance: Another form of focal presentation is a hypoechoic nodule with ill-defined margins .
This form is associated more frequently with diffuse involvement of the thyroid parenchyma.
These nodules are the most worrisome at the time of diagnosis because their appearance can be indistinguishable from thyroid lymphoma and papillary carcinoma,
especially if they present other signs suggestive of malignancy,
such as a thick hypoechoic and irregular halo,
hypervascularization or lobulated contours.
[5].
In these cases,
characterization with FNA is unavoidable due to the higher incidence of papillary carcinoma in thyroiditis.
- Hypoechoic area of geographic aspect: it corresponds to an area of geographical edges that does not present the same morphology in both planes. Fig. 15 It can be single or multiple.
Fig. 16
In our experience,
the presence of lymph nodes in the infrathyroid and/or anterior perithyroid adjacent to the isthmus (Delphian node) location,
uni or bilateral,
single or multiple; associated with the echographic patterns previously described,
are highly suggestive of Hashimoto's thyroiditis,
In the few references found in the literature,
juxtajugular (levels II-IV),
supraisthmic (Delphian node) and paratracheal (level VI) are described as the more frequent locations [7,
8,
9].
However,
in our experience,
the most characteristic are those located in the infrathyroid,
paratracheal and Delphian node regions,
since in the juxtajugular region there are often nonspecific lymph nodes not related to thyroiditis.
On ultrasound examination,
they are found from the initial stages of thyroiditis,
and their size varies from a few mm to more than 1 cm.
Fig. 17 The size is probably related to the activity of the disease,
since they are usually small in atrophic thyroid and large in enlarged and markedly hypervascular globular thyroids.
They should be looked for in the axial plane scanning,
where they are more easily detected.
Frequently,
adenopathies of the Delphian node region are confused with hypoechoic nodules in the isthmus.
It is essential to know them and recognize their oval morphology to correctly diagnose thyroiditis.
Fig. 18 In addition,
adenopathies in these locations do not appear in other thyroid pathologies such as goiter or multinodular thyroid,
which is so often confused with thyroiditis with a nodular pattern.
Given the frequency of concomitant benign and malignant thyroid disease and the propensity of malignant disease to metastasize to regional lymph nodes,
identifying these lymphadenopathies as part of thyroiditis is essential.
This finding,
together with the echographic pattern of homogenous echogenic nodules,
can give us the diagnostic clue,
and avoid misdiagnosis and more invasive tests,
such as fine needle aspiration (FNA) or biopsy.
In our experience,
the presence of perithyroid lymph nodes is,
by itself,
suggestive of thyroiditis of autoimmune origin,
even in the presence of a thyroid with practically normal or minimally heterogeneous parenchyma,
especially if it presents with biconvex or lobulated edges.
Fig. 19