Clinicopathological and Molecular Features of Secondary Cancer (Metastasis) to the Thyroid and Advances in Management

Thyroid gland: a rare site of metastasis

PURPOSE

Despite its rich vascularity, metastasis (MTS) to the thyroid tissue is unusual, ranging from 1 to 3%. This entity is not usually considered as differential diagnosis and is not included in the upfront approach in patients with thyroid nodules. Once diagnosed, treatment is controversial. The aim of this study was to evaluate diagnosis, treatment, and outcome at the end of follow-up in patients with a diagnosis of MTS to the thyroid.

METHODS

A retrospective multicenter study was designed from 1985 to 2022; 29 patients with MTS to the thyroid gland were included in the analysis.

RESULTS

Clinical presentation included the presence of a nodular goiter (65.5%), compression symptoms (17.2%), diffuse goiter (10.3%), and suspicious lymph nodes in the neck (7%). Primary tumor sites were: kidney (44.8%), breast (24.1%), lung (13.8%), neuroendocrine system (6.9%), colon (3.4%), cervix (3.4%), and ovary (3.4%). In 18/23 patients, suspicious ultrasound criteria for malignancy were described. Preoperative diagnosis was made in 23/27 patients by FNA and confirmed in 18 cases by immunohistochemistry. Seventeen patients underwent surgery. At the end of the follow-up, 19 patients had died of oncological disease, and six were alive (2/6 disease-free with isolated intrathyroidal MTS).

CONCLUSION

Renal carcinoma was the tumor that most frequently metastasized to the thyroid gland. Immunodiagnosis was a very useful tool for etiological confirmation. Patients with MTS to the thyroid gland as a unique site had a more favorable course compared to patients with multiple metastatic sites. Finally, outcomes and prognosis essentially depended on the biology of the primary tumor.

Investigation of pre-operative demographic, biochemical, sonographic and cytopathological findings in low-risk thyroid neoplasms

OBJECTIVE

The present article analyses pre-operative demographic, biochemical, sonographic and histopathological characteristics of low-risk thyroid neoplasms (LRTNs), with a focus on four subgroups, "well-differentiated carcinoma-not otherwise specified" (WDC-NOS), "non-invasive follicular thyroid neoplasm with papillary like nuclear features" (NIFTP), "well-differentiated tumours of uncertain malignant potential" (WDT-UMP) and "follicular tumour of uncertain malignant potential" (FT-UMP).

METHODS

The study retrospectively analyzed the histopathology of 2453 malignant thyroids and the final analyses included 99 cases diagnosed with LRTNs. The demographic and clinical features, pre-operative thyroid function, ultrasonography results, cytopathology results, histopathology results and prognostic classifications were assessed.

RESULTS

The groups were similar demographic characteristics and the majority of clinical data, including comorbidities, thyroid function tests, thyroid cancer/neck radiotherapy history. NIFTPs represented 69.7% of all LRTNs. All (100%) WDT-UMPs had solitary nodules. Index nodule volume differed among the groups (p = .036), it was the lowest in WDC-NOS [0.68 (0.63-0.72 cc)] and highest in FT-UMP [12.6 (0.5-64 cc)]. Echogenicity findings were similar. Index nodule TIRADS demonstrated a significant difference (p = .021) but index nodule halo sign and BETHESDA scores were similar in all groups. The diameter, localisation and multicentric structure of LRTNs were again similar for all groups. Finally, prognostic scores suggested similar outcomes in all groups.

CONCLUSION

The majority of LRTNs were NIFTPs in our population and all WDT-UMPs were solitary lesions. Index nodule volume was the most essential discriminating sonographic finding but further research must be performed before discriminatory potential can be described.

Metastatic Disease to a Concurrent Thyroid Neoplasm: A Case Series and Review of the Literature

BACKGROUND

Metastatic disease to the thyroid gland is uncommon but well-described. Metastatic disease to a concurrent primary thyroid neoplasm is a rare phenomenon. We sought to study patients with metastasis to the thyroid with a focus on the histopathologic and clinical features in tumor-to-tumor metastasis.

METHODS

We identified a series of patients with metastatic disease to the thyroid, with or without a concurrent primary neoplasm, through a search of the files of the Department of Pathology. All relevant slides were retrieved and reviewed, including routine HE and immunohistochemical stains. We performed a detailed English language literature search (1962-2022) and review to identify tumor-to-tumor metastasis involving the thyroid.

RESULTS

We identified 14 patients with metastasis to the thyroid over a 22-year period. Four patients exhibited papillary thyroid carcinoma, with metastatic spread of a different malignancy seeding into the thyroid cancer. We describe the histopathologic diagnostic process and findings, clinical management, and the clinical course of tumor-to-tumor metastasis in greater detail for these 4 patients.

CONCLUSION

Tumor-to-tumor metastasis to the thyroid is a rare event with unique histopathologic features. Our findings suggest that the phenomenon of tumor-to-tumor metastasis serves to highlight broader mechanisms of metastatic disease in general. We provide the largest-to-date and comprehensive review of the literature to identify all previous reported instances of tumor-to-tumor metastasis involving the thyroid.

Metastatic renal cell carcinoma to the thyroid with cervicothoracic venous tumor thrombosis

INTRODUCTION

Metastatic renal cell carcinoma (RCC) represents 25%-42% of metastatic thyroid malignancies. Propensity for RCC to demonstrate intravascular extension to the inferior vena cava is well documented. We present an analogous phenomenon of intravascular extension to the internal jugular vein (IJV) from thyroid gland metastasis.

METHODS

A 69-year-old male presented with metastatic RCC of the right thyroid lobe. Imaging demonstrated tumor thrombosis of the ipsilateral IJV, extending inferiorly to the junction of the brachiocephalic, subclavian, and internal jugular veins within the mediastinum.

RESULTS

Surgical excision required control of both the IJV in the neck and mediastinal venous great vessels via sternotomy, prior to subtotal thyroidectomy and venotomy for en bloc resection.

CONCLUSION

This case report describes metastatic RCC to the thyroid gland with cervicothoracic venous tumor thrombosis successfully treated with subtotal thyroidectomy, sternotomy for venotomy and tumor thrombectomy, and preservation of IJV conduit.

Neuroendocrine neoplasm with metastasis to the thyroid: a case report and literature review

Thyroid cancer can be divided into two types according to its cellular origin, i.e., malignant tumors originating from thyroid cells and cancers that metastasize to the thyroid from other sites, the latter of which are, clinically rare. This article reports the diagnosis and treatment of a rectal neuroendocrine neoplasm metastasis to the thyroid. No similar cases have been reported before. This case suggests that when evaluating thyroid tumors, clinicians should not only carefully identify the clinical features of the tumor but also pay special attention to the patient's history of tumors, especially neuroendocrine neoplasms. For definite secondary thyroid malignancies, neck surgery is feasible if the thyroid is the only site of metastasis; otherwise, the subsequent diagnosis and treatment plan should be determined after a comprehensive evaluation of the primary tumor and patient's general condition.

An update on the current epidemiological status of metastatic neoplasms to the thyroid

Secondary tumours to the thyroid gland are uncommon with an overall prevalence of 5.9% in autopsy studies. In recent clinical series, secondary thyroid cancer is seen in only 1.9% of malignant thyroids. There is no gender predominance both overall (female to male 1.07:1) and when stratified by common histological subtypes (renal cell carcinoma, lung adenocarcinoma and colorectal adenocarcinoma). The median age of patients diagnosed with metastatic thyroid tumours in major studies ranges from 54 to 68 years. Metastases are more frequent in patients with pre-existing or concurrent thyroid pathology. In autopsy studies, the most common primary sites are breast carcinoma and lung carcinoma. Renal cell carcinoma, lung carcinoma and breast carcinoma predominate in clinical series. Upper aerodigestive tract primaries often directly infiltrate the thyroid gland. The underlying frequency of a histological subtype, geographic prevalence and aggressiveness of primary cancer likely contributes to the incidence of metastasis in the thyroid gland. This is seen in case series from Asia where gastric and oesophageal primary cancers predominate. Secondary thyroid cancer can present metachronously (60%), synchronously (34%), or as the first presentation of the underlying cancer (6%). Late metastases and first clinical presentations of disease often originate from renal cell carcinomas while synchronous cases tend to originate from the lungs. Other common primary sites for first presentation of secondary thyroid cancer include the lung and oesophagus. Although rare, secondary thyroid cancer should be considered as a differential particularly in patients with previous malignancy, such as from the kidney, lung, or breast.