What is a thyroid nodule?
Dr Roberto Novizio, MD
Thyroid nodules are an almost para-physiological condition, therefore extremely common especially in people over 50 years old. The nodules in question are generally very small and benign. The benign nodules, which have no clinical significance, are much more common than malignant ones.
In the past, when the diagnostic techniques were not so good as today, only nodules of a certain size were diagnosed: first because they caused a compressive symptomatology towards the esophagus, trachea or larynx; secondly for aesthetic reasons.
Anamnesis is fundamental in the patient who has thyroid nodules. Family history is initially investigated to identify any predispositions to thyroid tumors and then move on to the history of the lump of the patient (if new onset, already present etc ...).
The physical examination assesses the consistency and relationships of the lump with the neighboring structures; nodules of elastic consistency, smooth and painless tend to be benign.
Blood tests allows you to determine if thyroid nodular pathology is associated with dystiroidism (alteration of thyroid function). The first test concerns TSH (thyrotropin) which, if altered, allows to carry out tests aimed at detecting the free fractions of thyroid hormones (freeT3 and freeT4).
If you have a lump and blood tests with high TSH, low fT3 and fT4 we are in a case of hypothyroidism. This condition is most frequently caused by one autoimmune condition.
If, on the other hand, a single lump is present, with TSH low or zeroed, fT3 slightly high and fT4 very high compared to the normal threshold, you are in a condition of hyperthyroidism that may be caused by the lump in the form of a hyperfunctioning autonomous adenoma (toxic or Plummer adenoma) or by Graves' disease.
Ultrasound is the gold standard for diagnosis in thyroid disease. This allows to detect and analyze microcalcifications, vascularization, peripheral halo, infiltrative forms and margins. These are not pathognomonic features, but if taken together they can strongly direct towards diagnosis of neoplasm.
Thyroid scintigraphy uses Technetium59 as a tracer, and is used to differentiate hot nodules from cold nodules. Scintigraphy was much more used in the past, when the ultrasound had not yet been perfected and therefore not able to identify the nodular characteristics. Today scintigraphy is used mainly to identify hyperfunctioning nodules that cause lower TSH.
Following these tests, if the clinical doubt arises that the lump may conceal a tumor, we proceed with an ultrasound-guided fine needle aspiration under ultrasound guidance followed by a cytological examination. If before they could only sting clinically visible nodules, today it is possible to prick nodules of a few millimeters thanks to the ultrasound guide.
Cytological examination reveals the nature of the lump: cystic, adenomatous, neoplastic, indeterminate.
In undetermined lesions normal thyrocytes (follicular cells) are identified, however these can be part of a follicular carcinoma. A carcinoma or a follicular adenoma is not distinguished through cytology (the structure of the thyrocyte remains normal) but through a histological examination (preceded by a biopsy) which allows to identify the infiltration of the capsule and the vessels and thus make a diagnosis of carcinoma follicular.
Cytological examination following needle aspiration can give different results:
- Tir1: non-diagnostic. This result may also be due to operator errors. About 20% of cytological samples is inadequate and to repeat a needle aspiration it is necessary to wait 2-3 months for the hematoma caused by the previous reabsorbs;
- Tir2: it is found simply colloid therefore it is an indication of a benign nodule;
- Tir3: follicular/indeterminate proliferations. Based on the number of cells and the presence of colloids, the pathologist tries to discern between: Tir3A or low risk malignancy nodules that need only follow up; and Tir3B or nodules with high malignancy risk that require surgical treatment;
- Tir4: suspected malignant nodule. Patients are referred to the surgeon.
- Tir5: malignant nodule. Patients are referred to the surgeon.