A developmental variant of the thyroid cartilage

A 32 year-old woman was referred for a neck sonography (US) due to a history of pain in the right submandibular area. Her past medical history was negative.

On ultrasound, the thyroid gland, the parotid and sub-mandibular glands were normal. We noted three homogenously hypoechoic well-defined avascular foci of up to 4 mm: two right-sided and one left-sided in the thyroid cartilage (Fig. 1).

Fig. 1.

Due to persistent pain, magnetic resonance imaging (MRI) of the neck was performed to assess these lesions and to exclude any lesions missed with US. On MRI, small well-defined structures with intermediate T1-weighted signal and high signal on the fat-suppressed sequence were seen on each side of the thyroid cartilage (Fig. 2).

Fig. 2.

No contrast enhancement was seen. MRI did not demonstrate any other pathology.

The final cause of the neck pain was not explained with MRI, but the clinical outcome of the patient was finally considered as normal.

The thyroid cartilage, the largest of the nine cartilages of the larynx, consists of two laminae of hyaline cartilage that fuse into the midline, forming the prominent V angle called laryngeal prominence or Adam’s apple⁽¹⁾.

The ossification process begins in the inferior portion of the posterior third of the lamina and inferior horn⁽²⁾. The anterior half of the cartilage usually ossifies at the late stage with a tendency to partial calcification at this level in the female population^(1,2). The unossified areas within the thyroid laminae often persist as radiolucent “windows” till an advanced age^(1,2).

The cyst-like formations of the thyroid cartilage are uncommon and are incidental findings on imaging, mainly seen in the adolescent age group⁽²⁾.

They are considered developmental variants and their appearances are correlated with the degree of mineralization and calcification occurring during adolescence⁽²⁾.

The differential diagnosis of thyroid cartilage lesions includes chondrosarcomas and chondromas. In these cases, abnormalities are visible on fiberoptic laryngoscopy, CT and MRI. Rare cases of degenerative cysts of the thyroid cartilage were reported in patients with a history of neck trauma⁽³⁾. Furthermore, some cases of early physiologic ossification of the thyroid lamina in children were reported and can mimic metastatic calcification⁽⁴⁾. In our case, the cyst-like formations were millimetric and symmetric without signs of malignancy. These are considered benign changes of thyroid cartilage with no clinical significance and do not require any additional assessment or follow-up⁽²⁾.

The aim of our case is to raise the awareness of this uncommon benign variant that may be encountered during a routine neck US. The awareness of this variant will clinch the diagnosis without further investigations.