24-year-old woman presented with a large neck mass involving thyroid and right lateral neck. According to the patient this mass originally started as a small nodule and has rapidly increased to the present size of 4.5 cm over the course of 6 months. She had a thyroid ultrasound which demonstrated right thyroid mass associated with right cervical adenopathy; indirect laryngoscopy showed extrinsic compression of trachea from right anterior aspect. Patient underwent CT neck, which showed a 4.5 cm mass centered on the right lobe of the thyroid gland, narrowing and displacing the trachea. Patient also had a PET/CT which showed an intensely FDG avid mass centered on the right lobe of the thyroid, narrowing and displacing the trachea with multiple FDG avid right cervical lymph nodes extending into the thoracic inlet.
Pathological/Microscopic Findings and any Immunohistochemical or Other Studies:
1. The fine needle aspiration specimen showed spindle to oval cells with even chromatin and faint to absent cytoplasm intermixed with groups of cohesive epithelial cells. The spindle to oval tumor cells were arranged in cohesive clusters with nuclear overlapping, crowding and molding. Vascular proliferation was also noted among the cell groups. No nuclear features of papillary carcinoma were seen. The cell block demonstrated strips of stratified columnar epithelium. The tumor cells were negative for thyroglobulin and calcitonin and positive for cytokeratin, TTF-1 and WT-1.
2. Primitive neuroectodermal tumor
3. Malignant teratoma
4. Anaplastic carcinoma
Malignant Teratoma of the Thyroid. The correct diagnosis was rendered on histopathologic follow-up which showed primitive neural elements intermixed with bronchial and glandular elements and cartilage. The tumor showed vascular invasion, extrathyroidal extension and metastases to multiple neck lymph nodes. Immunohistochemical profile: Epithelial elements of the tumor were strongly positive for cytokeratins AE1/AE3 and pancytokeratin. Bronchial-like glandular elements were strongly positive for TTF-1. Thyroglobulin highlighted the surrounding and entrapped normal thyroid follicles. The primitive blastema component was strongly positive for Sall4; myogenin and desmin stained a subset (approximately 10%) of the blastema. An immunostain for chromogranin showed in rare epithelial cells within the primitive neural elements; Immunostains for calcitonin and S-100 were negative.
The head and neck region accounts for approximately 5% of all benign and malignant germ cell tumors. These have been reported in soft tissues of the neck, thyroid, superficial facial structures, oral cavity, nasopharynx and orbit. Benign teratomas of thyroid usually occur in children; however, teratomas in adults are rare and are frequently malignant. They are more common in young woman, present as large neck mass with associated lymphadenopathy and metastatic disease. The diagnostic criteria for a malignant teratoma of thyroid include: tumor present within the thyroid gland, the gland is absent or replaced by tumor and the gland is in continuity with the tumor. On light microscopy these tumor demonstrate a predominance of primitive neuroepithelial component admixed with blastema like stroma, mature squamous or glandular epithelial elements and mature cartilage. It has been shown that thyroid teratomas can cause significant morbidity due to respiratory distress or the presence of associated malformations of neck organs. However, in adults the microscopically malignant teratomas follow an aggressive course i.e. regional and distant metastases.
-Establishing the diagnosis of malignant teratoma of the thyroid can be difficult in fine-needle aspiration specimens. -The cytologic specimens usually show spindle to oval cells with even nuclear chromatin and faint to absent cytoplasm intermixed with groups of cohesive epithelial cells.
-The diagnosis of malignant teratoma is based upon clinical presentation, identification of various tissue elements, the immature/malignant neural tissues, and confirmation by immunohistochemical stains.
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- Djalilian HR et.al Malignant teratoma of the thyroid: Review of literature and report of a case. Am J Otolaryngol 2000;21:112-115.
- Perez-Mies, B et.al Malignant teratoma of the thyroid in a pregnant woman. Ann Diag Pathol 2010;14;264-267.