Fine‐needle aspiration biopsy of secondary neoplasms of the thyroid gland: A multi‐institutional study of 62 cases

Abstract

BACKGROUND: Secondary neoplasms of the thyroid gland (SNTGs) are uncommon, and it is important to recognize them in thyroid fine-needle aspiration biopsy (FNAB). METHODS: The authors report a cohort of 62 SNTGs from 7 institutions in the United States and Europe. Patients were identified retrospectively by searching through medical records of the respective institutions. All initial diagnoses were rendered by FNAB. RESULTS: SNTGs represented 0.16% of all thyroid FNABs and were more frequent among women (ratio of women to men, 1.2:1.0). The mean patient age was of 59 years (range, 7-84 years), the mean tumor size was 3 cm (range, 0.9-7 cm), and the mean interval from diagnosis of the primary tumor was 45 months (range, 0-156 months). Eighty-seven percent of SNTGs were diagnosed as malignant by FNAB, and there was a specific SNTG diagnosis in 93% of patients. Immunocytochemistry and flow cytometry, which were used in 30% of patients, were useful ancillary studies. Adenocarcinomas (n 5 23; 37%) and squamous cell carcinomas (SCCs) (n 5 22; 35.5%) represented the majority of SNTGs, followed by lymphoma (n 5 5; 8%), melanoma (n 5 5; 8%), adenoid cystic carcinoma (n 5 3; 5%), and various sarcomas (n 5 3; 5%). Adenocarcinomas originated from the kidney (n 5 9; 39%), lung (n 5 6; 26%), breast (n 5 5; 22%), and colon (n 5 3; 13%). SCCs originated mostly from the head and neck (n 5 13; 59%), followed by lung (n 5 3; 13%), esophagus (n 5 3; 14%), and unknown primary sites (n 5 3; 14%). CONCLUSIONS:Adenocarcinomas from the kidney, lung, breast, and colon along with SCCs represent the majority of SNTGs. The current results indicate that FNAB is a sensitive and accurate method for diagnosing SNTG; however, diagnostic difficulties can occur. Knowledge of clinical history and the judicious application of ancillary studies can increase the sensitivity and accuracy of FNAB for detecting SNTGs. Cancer (Cancer Cytopathol) 2015;123:19-29. V C 2014 American Cancer Society.KEY WORDS: thyroid; secondary neoplasm; metastasis; renal cell carcinoma; squamous cell carcinoma; adenocarcinoma; lymphoma; adenoid cystic carcinoma; fine-needle aspiration; cytology. INTRODUCTIONSecondary neoplasms of the thyroid gland (SNTGs), representing either metastases or direct extension of tumors from adjacent anatomic structures, are uncommon. Their reported incidence varies substantially, however, ranging from 0.1% to 3% in clinical series. 1-15 They have been reported as incidental findings in autopsy studies [16][17][18] with a frequency of 4.4% to 24% in patients with a known primary cancer or widespread Original Article malignancy in which clinically occult thyroid micrometastases may be detected. 4,[19][20][21][22] In the United States and Europe, the most commonly reported primary tumor resulting in symptomatic SNTG is renal cell carcinoma (RCC), closely followed by carcinomas of the breast, lung, and colon. 5,23-25 Secondary lymphoma, melanoma, sarcoma, and head and neck squamous cell carcinoma (SCC) also account for a significant proportion of SNT...

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“…But this explanation is not complete as the percentage of males among patients with metastases of those tumours was two-times higher than that among all the patients with these tumours subjected to FNA (Table I). Similarly, in other studies [14,17,28,30] males constituted 40%-50% and even more than 70% [15] of patients with metastasis to the thyroid gland. It should also be stressed that the percentage of males among patients with secondary thyroid tumours was much higher than the percentage of males among patients with primary thyroid cancers, which in our data was 11% [31].…”

“…Early diagnosis including a thyroid FNA result allows the avoidance of unnecessary thyroid surgery in some cases. On the other hand, when analysis is mainly based on biopsy results, the limitation is a frequent impossibility to distinguish primary, especially non-differentiated, thyroid cancers from secondary tumours [11,14,[23][24][25]. In such cases the FNA result indicates only the need to take into account…”

“…After taking into account the relative frequency of metastases (in relation to the number of patients subjected to FNA with a specific cancer) we observed that the dominant type of metastases was a tumour infiltrating the thyroid by direct extension from the neighbouring primary lesion. Also other authors showed that tumours of the head and the neck were the most common [14][15] or frequent [8] source of metastasis. However, most of the authors limited their analyses to metastases from distant organs only.…”

“…Metastases to the thyroid are revealed clinically with a frequency of 0.1-3% in patients diagnosed or operated for thyroid nodules/cancer [1,[7][8][9][10][11][12][13][14][15][16]. Hegerova et al found metastases in 97 out of 10,798 (0.9%) patients identified from a database of cytological material archived over 30 years at the Mayo Clinic [17].…”

Malignant melanoma with synchronous thyroid metastases: case report and literature review

“…Despite the high sensitivity of FNAB for the diagnosis of metastases to the thyroid gland, the accuracy of FNAB is between 50% and 90% (19,(23)(24)(25). This difference can be attributed to the experience of the center performing the FNAB (23).…”