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.

A Rare Case of Metastasis of Renal Clear Cell Carcinoma to the Thyroid Gland, Presenting as a Goiter Nodule, Three Years After Nephrectomy

Thyroid gland metastatic tumors are rare in clinical practice. Clear cell RCC is one of common metastatic tumors to thyroid. We here reported a case of incidentally found clear cell renal carcinoma metastasis to the thyroid gland 3 years after nephrectomy, in the thyroidectomy procedure performed for the patient due to the thyroid enlargement caused by multinodular goiter. A 65-year-old Iranian man with a history of multinodular goiter referred to our surgery clinic for thyroidectomy because of compressive effects on the trachea. Patient had a history of nephrectomy due to clear cell RCC 3 years ago. After thyroidectomy, gross and histological examination of thyroid revealed clear cell renal carcinoma metastasis to the thyroid gland in the setting of a multinodular goiter. The diagnosis was confirmed by immunohistochemistry staining. Patients with multinodular goiter are more prone to present with metastasis to thyroid gland if they have a history of malignancy, especially renal cell carcinoma.

Prevalencia de tumores metastásicos en la glándula tiroides. Revisión sistemática y metanálisis

Introducción y objetivo: Los tumores metastásicos en la glándula tiroides complican el diagnóstico, el tratamiento y el pronóstico del paciente. El objetivo es conocer la prevalencia de las metástasis en la glándula tiroides referida en la literatura médica y los tumores primarios que con más frecuencia metastatizan en la glándula tiroides. Método: Se realizó una revisión bibliográfica sistemática en las bases de datos de PubMed, La Biblioteca Cochrane y Scopus. Los artículos seleccionados se dividieron en dos grupos, series clínicas de pacientes en los que se hallaron metástasis en tiroides (grupo A) y series de hallazgos de metástasis en tiroides en autopsias (grupo B). Se realizó metanálisis de prevalencia para cada grupo de artículos siguiendo el modelo de efectos aleatorios. Resultados: La prevalencia en cada grupo con su índice de confianza al 95% fue 0.00479 (0.002-0.007) para el grupo A y 0.0362 (0.014-0.059) para el grupo B. La prevalencia de metástasis halladas en autopsias fue 7,58 veces mayor que en los estudios clínicos. En el grupo A la edad media fue 60.82 y en el grupo B 57.20. En ambos grupos las metástasis halladas en tiroides fueron más frecuentes en el sexo femenino. La localización del tumor primario fue diferente en ambos grupos, en el grupo A fue el cáncer de riñón y en el grupo B el cáncer de mama. La variabilidad de la prevalencia de metástasis en tiroides en los diferentes artículos de ambos grupos hace que este estudio tuviese una alta heterogeneidad (índice I2 y Q). Los funnel plot de ambos grupos indicaron alto sesgo de publicación. Discusión: La diferente prevalencia entre series clínicas y autopsias puede implicar que la detección de metástasis en tiroides en la clínica está infradiagnosticada. La razón de esto podría ser que las metástasis intratiroideas se presentan de forma asintomática siendo diagnosticadas como hallazgo casual en autopsias. En otras ocasiones se presentan como un nódulo tiroideo años después del tumor primario, lo que condiciona el diagnóstico. Conclusiones: La prevalencia de metástasis en tiroides es superior en las series de autopsias que en series clínicas (hasta 6.67 veces más frecuente en nuestro estudio). Las metástasis intratiroideas probablemente están infradiagnosticadas por cursar sin clínica siendo diagnosticadas como hallazgo casual en autopsias. Los tumores primarios más frecuentes fueron el riñón (series clínicas) y la mama (series de autopsias).

Diagnosis and Treatment of Metastases to the Thyroid Gland: a Meta-Analysis

The thyroid is a rare site of clinically detectable tumor metastases; even though the gland is a highly vascularized structure, the frequency of metastases in the routine practice is less than 0.2% of all thyroid malignancies. The purpose of our meta-analysis is to evaluate the frequency of metastatic diffusion from other primary tumors to the thyroid gland and to suggest the best possible treatment through an evidence-based study. Relevant studies were identified by searching the following databases: PubMed, Scopus, and Web of Science. We selected all English-written articles published from 1995 to 2015. Studies were considered eligible if they reported the timing of metastatic spread and the site of the primary tumor in respect to the diaphragmatic region. Case reports were not included. Twenty-eight studies accounted for 514 patients. The rate of metachronous metastases was 69%. Fifty-three percent of primaries originated from the infradiaphragmatic region. Fine needle aspiration biopsy (FNAB) was done in 154 patients and 195 patients were treated mostly with surgery. A prevalence of primary tumors from the infradiaphragmatic region and of metachronous metastases was observed. Knowledge of the clinical history and the ancillary techniques can improve the sensitivity and accuracy of FNAB. Thyroidectomy may be considered a more effective treatment than radio-chemotherapy.

Survival after renal cell carcinoma metastasis to the thyroid: single center experience and systematic review of the literature

BACKGROUND

Renal cell carcinoma can metastasize to uncommon sites, for example, the thyroid gland where metastases are rarely found. To determine the patient survival and the time between cancer diagnosis and thyroid metastasis, we analyzed a large patient cohort from our hospital records and performed a systematic review.

PATIENTS AND METHODS

Patients diagnosed between 1978 and 2007 with thyroid metastases from renal cell carcinoma were retrospectively identified from the hospital database. A systematic literature search was performed for publications describing at least three cases of thyroid metastasis from renal cell carcinoma. Case data from the identified studies were collected and used to determine the survival data.

RESULTS

We identified 34 patients (19 females) from our hospital records with a mean age of 67 years (range, 33-79) when thyroid metastasis was diagnosed. Median time to primary metastasis after resection of renal cell carcinoma was 6.5 years (range, 0-25) with a single case of synchronous metastasis. Median survival after primary metastasis was 4.7 years (95% confidence interval [CI]: 1.8-7.6). The systematic review included 32 studies with 285 patients. Case data could be extracted for 202 patients. Median time to thyroid metastasis (without synchronous cases) was 8.8 years (95% CI: 7.5-10.1). Median actuarial survival after thyroid metastasis was 3.4 years (95% CI: 2.2-4.6). Total thyroidectomy was not associated with a better survival compared to partial thyroidectomies.

CONCLUSIONS

Time to thyroid metastasis of renal cell carcinoma can be very long, and survival after thyroidectomy is favorable compared to metastasis to other sites.