A Rare Case of Cervico-Mediastinal Thyroid Teratoma (2024)

Monitoring Editor: Alexander Muacevic and John R Adler

Abstract

Teratomas are rare germ cell tumors derived from multiple germinal cell layers. Thyroid teratomas, specifically, are exceptionally uncommon and present unique diagnostic and therapeutic challenges. Here, we report a case ofcervico-mediastinalthyroid teratoma, highlighting diagnostic difficulties and surgical management. A37-year-old woman presented with right lateral cervical swelling, leading to radiological imaging suggesting a thymic teratoma. However, cytology indicated a colloid cyst. Surgical removalwas performed, revealing a mixed-type teratoma originating from the thyroid gland. Thyroid teratomas pose diagnostic and therapeutic challenges due to their rarity and complex nature. Further research is needed to establish standardized guidelines for their management.

Keywords: cervico-mediastinal thyroid teratoma, germ cell tumors, thyroid, mediastinum, teratoma

Introduction

Teratomas are a widespread form of germ cell tumors and histologically are defined as tissues derived from the 3 germinal cell layers: ectoderm, mesoderm, and endoderm. These cellsare capable of differentiating, giving rise to all the various tissues of the organism[1].Therefore, the conformation can differentiate in several types of tissues: thyroid, bone, muscle, cartilaginous, andtooth buds. Tumors in the head and neck represent 5% of all benign and malignant germ cell tumors and 6% of all teratomas.[2]Teratomas that arise in the neck are rare, and even fewer are located within thyroid tissue[3]. This article highlights the difficulties of a correct diagnostic procedure and correct operative timing in the teratomas of the cervical-mediastinal district, which are extremely rare.

Case presentation

A 37-year-old woman with no comorbidities andnegativemedical history, except for a right hemithyroidectomy 14 years before for benign disease, came to our observation for right lateral cervical swelling for some months. Therefore, thepatient underwent an MRI describing an oval formation affecting the upper thoracic layer (51x35x66 mm) with non-hom*ogeneous contrast impregnation due tothe presence ofgross calcification and an area with an adipose component. The formation was contiguous to the thymic tissue and was expressed in the right lateral-cervical compartment until it reached the thyroid plane.A neck-chest CT scan with contrast enhancement was performed,which highlightedan expansive lesion in the anterosuperior mediastinum, with maximum dimensions on the axial plane equal to 62x42 mm anda maximum extension on the coronal plane equal to 85mm.

This lesion appeared to be in continuity with the thymic tissue, caudally, with the left innominate vein compressed and markedly thinned, posteriorly, and the right innominate vein, the brachiocephalic arterial trunk, and the trachea slightly displaced to the left side. Cranially, it extended into the right thyroid lobe, previously removed. Furthermore, the appearance of a fluid/adipose component density was highlighted, extending anteriorly at the base of the neck in the median area where it reached the skin (Figure1).Radiological investigations indicated a thymic teratoma.

Therefore, the patient performed fine needle aspiration of the lesion, which highlighted blood fibrin material, some colloid globules, andvery rarecellular elements (TIR1 according to the Italian classification SIAPEC-AIT 2014; Bethesda 1 according to Bethesda system, 2023). Due to the non-diagnostic cytological findings, after a multidisciplinary agreement, surgery was decided to remove the lesion. After fine needle aspiration, the patient developed a chronic inflammatory process with cutaneous fistulisation of the neoformation. Antibiotic therapywas undertakenbefore surgery. Surgerywas performedthrough a collar cervicotomy. Detachment of the subcutaneous layers and divarication of the sternohyoid muscles and sternothyroid muscles appeared difficult due to tenacious adhesions resulting from a chronic inflammatory process and recent cutaneous fistulization affecting the right thyroid lodge with the skin, with consequent subversion of the vascular-muscular structures. As for teratoma, the neoformation presented a capsule containing calcified nodules, caseous material, and hairs. Surgical removalwas performeden bloc after sectioning the peduncle at the thyroid isthmus, and the specimenwas sentfor definitive histological examination (Figure2).

The left thyroid lobe showed nosigns ofdisruption andwas leftin place. An accurate skin surgical closureincludedthe previous fistulous passage between the lesion and the skin. On microscopic examination, skin and cutaneous appendage, commonly found in mature teratoma, were seen (Figure3a). Respiratory mucosa, adipose tissue (Figure3b), and mature brain tissue (Figure3c)wereclearlyidentified. In this case, an interesting pseudopapillary stroma changewas observed, resembling morphologically the intravascular papillary endothelial hyperplasia (Figure3d).

After an accurate examination, no immature componentwas found. Based on these histologic and macroscopic findings, mature teratomawas diagnosed. After four months after surgery, the patient performed a new contrast CT scan that did not document signs of macroscopic disease recurrence. The patient did not undergo any post-surgery therapy and was alive and disease-free at the last follow-up of 16 months.

Discussion

Various theories propose the origin of teratomas, one of which involves migrating primordial germ cells from the extraembryonic mesoderm to the genital ridges. Others suggest that during the fourth and fifth weeks of gestation, among the endodermal cells of the yolk sac that migrate to the gonadal ridges, some may not reach their intended destination and cause teratomas to develop anywhere between the brain and the coccygeal area, typically in the midline[1].

Mature teratomas are generally benign tumors whose structureis characterizedby more than one mature differentiated tissue, such as skin, hair, teeth, muscle, and nervous tissue. They grow slowly and are almost always asymptomatic, so much so that theyare occasionally discoveredduringradiodiagnostictests performed for other reasons. They can rarely cause symptoms when they grow and compress vital structures, causing dyspnoea[2]. Primary thyroid teratomas are rare thyroid gland neoplasms of germ-cell derivation that display features of trilineage differentiation[3]. Benign lesions of thyroid teratomas are more commonly observed in children or infants, whereas malignant cases are predominant among adults[4]. Malignant thyroid teratomas typically manifest with an initial neck mass, often accompanied by lymphadenopathy, which can progress to metastasis, primarily affecting the lungs[3].

The thyroid gland is accepted as the site of origin for the teratoma if (i) the tumor occupies a portion of the thyroid gland, (ii) there is direct continuity between the tumor and the thyroid gland, or (iii) the tumor has replaced the gland (no thyroid gland is identified intraoperative or by imaging)[5]. Lurje's description of malignant teratoma of the thyroid in adults dates back to 1908 when he reported a case involving a 53-year-old woman. She underwent a hemithyroidectomy, but she died during the surgical procedure[3-4].

Thyroid teratoma diagnosis poses challenges with fine-needle aspiration cytology (FNAC) due to frequently yielding indeterminate or unreliable results[6]. Complications such as teratoma rupture are relatively rare, according to a recent study by Ota E et al.[7], with only 56 cases of mediastinal teratoma rupture reportedto date. In the case described by the authors[7], the rupture of a mature teratoma in a 29-year-old girl caused mediastinitis, requiring emergency surgical resection within 24 hours.

As thyroid teratoma is rare, treatment lacks established guidelines. However, most documented cases involve complete surgical excision followed by adjuvant therapy comprising chemotherapy, radiation, or a combination of both. There are a few cases in the literature that underwent just a partial thyroidectomy with chemotherapyand/orradiotherapy and did not require a completion thyroidectomy or complete nodal clearance[3].

In our case, the patient noticed cervical swelling, for which she decided to undertake further diagnostic investigations. The diagnosis was not immediate, and there was a discrepancy between the cytological and radiological examinations withouta realguideline for diagnosing teratomas of thecervico-mediastinaldistrict. Furthermore, the lack of adequate studies makes establishing the correct operative timing impossible. In our case, macroscopically, the teratoma had a direct continuity with the thyroid gland[4].

When a tumor comprises immature and malignant components alongside areas resembling mesenchymal and neural tissue, it necessitates a thorough differential diagnosis.Thisincludes distinguishing it from other malignancies such as anaplastic carcinoma, carcinosarcoma, Ewing sarcoma, primitive neuroectodermal tumor, small cell carcinoma, and malignant lymphoma[8]. Also, in our case, especially for the radiological aspects, a tumor with a thymic origin was hypothesized.

The histology of the tumor is indicative of the disease's aggressiveness. Tumors graded as 0 consist solely of mature elements and are generally deemed benign. Those graded as 1 or 2are consideredimmature, while grade 3 tumors, characterized by immaturity, are typically classified as malignant. The presence of embryonal carcinoma or yolk sac tumor places teratomas in the malignant category[9]. Diagnosing primary thyroid teratoma presents a challenge to pathologists due to its complexity and rarity.

According to a recent scientometric analysis on teratomas conducted by Murat Çalbiyik and Sinan Zehir, Italy is the tenth country (136 publications, 3.2%) that contributed to the global literature on teratomas from 1980 to 2022. The analysis revealed that the topics most studied are ovarian teratoma, ovarian dermoid cysts, sacrococcygeal teratoma, and immature teratoma types. After these teratomas, they focus on topics related to mediastinal teratoma, testicular teratoma, and retroperitoneal teratoma[10].

Conclusions

There are no standard strategies for treating thyroid teratoma that can help clinicians make decisions for each case. Correct surgical timing is essential to avoid complications. Our study aimed to highlight the need for further studies on this pathology.

Acknowledgments

Alessandra Cancellieri for contributing to the histopathological diagnosis.(alessandra.cancellieri@policlinicogemelli.it, Division of Anatomic Pathology and Histology, Fondazione Policlinico Universitario “Agostino Gemelli” IRCCS, Università Cattolica del Sacro Cuore, Rome, Italy).

Notes

The authors have declared that no competing interests exist.

Author Contributions

Human Ethics

References