Thyroid tissue outside the thyroid gland: Differential diagnosis and associated diagnostic challenges

Personalized Management of Malignant and Non-Malignant Ectopic Mediastinal Thyroid: A Proposed 10-Item Algorithm Approach

We aimed to analyze the management of the ectopic mediastinal thyroid (EMT) with respect to EMT-related cancer and non-malignant findings related to the pathological report, clinical presentation, imaging traits, endocrine profile, connective tissue to the cervical (eutopic) thyroid gland, biopsy or fine needle aspiration (FNA) results, surgical techniques and post-operatory outcome. This was a comprehensive review based on revising any type of freely PubMed-accessible English, full-length original papers including the keywords "ectopic thyroid" and "mediastinum" from inception until March 2024. We included 89 original articles that specified EMTs data. We classified them into four main groups: (I) studies/case series (n = 10; N = 36 EMT patients); (II) malignant EMTs (N = 22 subjects; except for one newborn with immature teratoma in the EMT, only adults were reported; mean age of 62.94 years; ranges: 34 to 90 years; female to male ratio of 0.9). Histological analysis in adults showed the following: papillary (N = 11/21); follicular variant of the papillary type (N = 2/21); Hürthle cell thyroid follicular malignancy (N = 1/21); poorly differentiated (N = 1/21); anaplastic (N = 2/21); medullary (N = 1/21); lymphoma (N = 2/21); and MALT (mucosa-associated lymphoid tissue) (N = 1/21); (III) benign EMTs with no thyroid anomalies (N = 37 subjects; mean age of 56.32 years; ranges: 30 to 80 years; female to male ratio of 1.8); (IV) benign EMTs with thyroid anomalies (N = 23; female to male ratio of 5.6; average age of 52.1 years). This panel involved clinical/subclinical hypothyroidism (iatrogenic, congenital, thyroiditis-induced, and transitory type upon EMT removal); thyrotoxicosis (including autonomous activity in EMTs that suppressed eutopic gland); autoimmune thyroiditis/Graves's disease; nodules/multinodular goiter and cancer in eutopic thyroid or prior thyroidectomy (before EMT detection). We propose a 10-item algorithm that might help navigate through the EMT domain. To conclude, across this focused-sample analysis (to our knowledge, the largest of its kind) of EMTs, the EMT clinical index of suspicion remains low; a higher rate of cancer is reported than prior data (18.8%), incident imagery-based detection was found in 10-14% of the EMTs; surgery offered an overall good outcome. A wide range of imagery, biopsy/FNA and surgical procedures is part of an otherwise complex personalized management.

Two Cases of Adrenal Cysts Lined by Thyroid Follicular Epithelium: Addressing Cellular Origin and Malignancy Concerns

Adrenal cysts lined by thyroid follicular epithelium are rare, with only 14 reported cases of "ectopic thyroid tissue" to date. While the primary consideration for differential diagnosis is thyroid carcinoma metastasis, exclusion of metastases is determined based on the absence of a primary thyroid lesion, serological euthyroidism, lack of thyroglobulin elevation, and absence of epithelial atypia. Herein, we report 2 cases of adrenal cysts lined by thyroid follicular epithelium. Case 1 was a 60-year-old woman with a right adrenal cyst. Case 2 was a 51-year-old man with a left adrenal cyst. Over time, both cysts became larger, necessitating an adrenalectomy. Cystic epithelia were lined with thyroid follicular epithelium, exhibiting moderate atypia. Human bone marrow endothelial cell marker-1 and galectin-3 were focally positive; CK19 was positive in Case 1, and all 3 markers were positive in Case 2, previously reported as an immunophenotype of thyroid carcinoma. CD56 expression was positive in both cases. Targeted next-generation sequencing revealed several low-frequency mutations; however, no major driver alterations for thyroid cancer were detected. Adrenal cysts can be lined by thyroid follicular epithelium. Challenges arise in determining the malignant or benign nature of adrenal cysts.

Synchronous lateral lymph node metastases from papillary and follicular thyroid carcinoma: case report and review of the literature

Background

Follicular thyroid carcinomas (FTCs) rarely metastasize to regional lymph nodes, and descriptions of synchronous lateral lymph node metastases of FTC and papillary thyroid carcinoma (PTC) are lacking.

Case Presentation

We describe a 43-year-old female with a preoperative cytology indicating a right-sided PTC with lateral lymph node metastases. She underwent a total thyroidectomy and central and lateral lymph node dissection, and histopathology confirmed a multifocal tall cell variant PTC together with a 12 mm minimally invasive FTC in the ipsilateral lobe. While the central compartment demonstrated metastatic PTC, the lateral compartment contained PTC metastases alongside a 15 mm large follicular-patterned mass in a separate lymph node. As the cells lacked PTC associated nuclear changes, the possibility of a lateral lymph node metastasis of FTC was considered, with the possibility of ectopic thyroid tissue as a differential diagnosis. By utilizing next-generation sequencing, a Q61R NRAS mutation was pinpointed, thus proving the tissue as tumorous. The patient underwent radioiodine treatment and is currently monitored following a negative whole-body scan.

Conclusions

This is probably the first case report of a patient with co-existing lateral lymph node PTC and FTC metastases. Consulting previous publications, there is currently a gap of knowledge in terms of how patients with regional FTC metastases should be followed-up and treated, especially when co-occurring with spread high-risk PTC subtypes. Moreover, what guides a seemingly indolent FTC to spread via the lymphatic system remains to be defined from a molecular standpoint.

Chronic thyroiditis in lateral ectopic thyroid mimicking cervical metastasis of thyroid cancer

SUMMARY

We present the case of a 45-year-old Caucasian woman who attended the Endocrinology Unit for a left cervical mass discovered during follow-up for autoimmune chronic thyroiditis. The ultrasound-guided fine-needle aspiration biopsy of the lesion was consistent with a metastasis of follicular thyroid carcinoma. The sonographic neck evaluation revealed no thyroid nodules but three markedly hypoechoic and highly vascularized areas, with irregular margins and hyperechoic spots. In the clinical suspicion of primary thyroid neoplasm, ultrasound-guided fine-needle aspiration biopsy of two of the three areas was performed, but both cytological reports were non-diagnostic, revealing only colloid and blood. Subsequently, the patient underwent surgical removal of the cervical mass, with the intra-operatory consultation with frozen section examination suggesting follicular-like neoplasia. For this reason, thyroidectomy with both central and lateral neck dissection was performed. Surprisingly, the final histologic examination revealed chronic thyroiditis in the thyroid specimen and no evidence of metastasis in the left neck mass. Consequently, the pathological revision of the frozen section assessment led to the final diagnosis of chronic thyroiditis on the lateral ectopic thyroid. This case represents an uncommon example of lateral ectopic thyroid tissue with coexisting normally located thyroid tissue both affected by chronic thyroiditis.

LEARNING POINTS

Ectopic thyroid must be considered in the diagnostic work-up of lateral neck mass. Even if rare, ectopic thyroid tissue can be found lateral to the carotid sheath and with coexisting normally located thyroid tissue. As the orthotopic tissue, lateral ectopic thyroid tissue can be affected by chronic thyroiditis, which may complicate the diagnosis both on ultrasound and cytology.