Purpose or Case Report:


The incidence of thyroid nodules in the pediatric population is low, ranging from approximately 0.5% to 5%. The risk of malignancy is higher than in adults.
ultrasound is considered the “gold standard” for an accurate and reliable evaluation of thyroid nodules, identifying predictors of malignancy.
Epidermoid cysts (EC) can be distinguished from dermoid cysts, and EC are extremely rare with fewer than 20 cases reported, only two of them involved pediatric patients.
Due to the content of keratin and squamous cells, the epidermoid cyst may present a solid ultrasound appearance with echogenic punctiform images that could simulate calcifications, even in the color Doppler examination it could present scintillation artifact. Therefore, cytologic evaluation is essential in the diagnosis, and shows sheets of anucleated squamous cells mixed with few nucleated ones with absence of cellular atypia, granuloma or thyroid epithelial cells
Methods & Materials: We present a 6-year-old male patient, with no relevant pathologic history, who consulted for a painless left laterocervical tumor of 6 months of evolution.
Results:

Ultrasound showed a solid nodule with regular margins at the left thyroid lobe, of heterogeneous echogenic structure with dotted echogenic images, with no vascularization on Doppler examination; the rest of the gland showed no alterations and no adenomegaly was detected.
An ultrasound-guided fine-needle aspiration biopsy was performed, but the sample was insufficient (Bethesda I). A total thyroidectomy was scheduled due to suspicion of malignant pathology. Intraoperative frozen section analysis demonstrated squamous epithelial cells consistent with an epidermoid cyst, leading to the decision to perform a left hemithyroidectomy.
Conclusions:

Intrathyroidal EC is extremely rare in clinical practice. The appearance of the thyroid nodule on ultrasound evaluation may mimic the radiologic features of a solid thyroid neoplasm.
The possibility of an Intrathyroidal EC should be considered when benign squamous cells without follicular cells are found in a thyroid aspirate and can be successfully treated with hemithyroidectomy.