Abstract
Background
Poorly differentiated carcinoma is a rare epithelial tumor that falls between well-differentiated thyroid carcinoma and anaplastic thyroid carcinoma in terms of morphologic appearance and biologic behavior. An insular variant was characterized in 1983. Further study of this neoplasm is warranted owing to its high aggressiveness, propensity to local recurrence and distant metastases, and high associated mortality. Since insular thyroid carcinoma may have varied presentations, treatment should be individualized.
Purpose
To describe the experience of a major tertiary medical center with insular thyroid carcinoma over a 7-year period.
Material and methods
The study sample consisted of 17 patients with poorly differentiated thyroid cancer, insular variant, who were treated and followed at the Department of Otolaryngology, Head and Neck Surgery of Rabin Medical Center, Israel, in 1992–2009. The medical files were reviewed for background data, clinicopathologic features, treatment, and outcome.
Results
The study group included 10 men and 7 women with a mean age of 63 years (range 16–78). Initial treatment was total thyroidectomy, in a single session ( n = 9) or two sessions ( n = 8), followed by radioiodine ablation. In addition, five patients received postoperative external beam radiation and one patient received chemotherapy. Nine patients had extrathyroidal extension, seven had vascular invasion, and four had multifocal disease. Distant metastases were present in four patients. Follow-up ranged from 6 months to 12 years. At present, 11 patients are alive and well. Five died of disease, and one died of another cause.
Conclusion
Insular thyroid carcinoma is aggressive and difficult to treat. Surgery remains the mainstay of treatment, though multimodality therapy is usually required.
1
Introduction
Thyroid carcinoma is the most frequent neoplasm of the endocrine glands. Ninety percent of thyroid carcinomas are well differentiated. Poorly differentiated thyroid carcinoma (PDTC) was classified by the WHO in 2004 as a tumor of follicular cell origin that has morphologic and biologic attributes intermediate between well-differentiated (papillary and follicular) and anaplastic thyroid carcinomas . An insular variant was first reported in 1907 by Langhans and histologically characterized in 1983 by Carcangiu et al. as consisting of well-defined nests or “insulae” of cells with round, “dark,” and monomorphic nuclei and scant cytoplasm. This resembles the nests of cells seen in insular carcinoid and was thus initially termed insular thyroid carcinoma. Studies have shown that they arise from follicular epithelial cells with distinct biologic features and often produce thyroglobulin and concentrate radioiodine . According to most series, insular PDTC accounts for 4% to 8% of all thyroid carcinomas although others report a much lower incidence . The majority of studies of PDTC focused on the insular variant , but owing to its rarity, data on tumor behavior and patient prognosis are still insufficient. Further research of PDTC is important because they have a more aggressive clinical course than conventional follicular and papillary carcinomas, with a high incidence of local recurrence, early cervical lymph node involvement, and regional and distant metastases, most often in the bones and pulmonary tissue . Chao et al. reported rates of 50%–84% for lymph node metastases and 36%–84% for distant metastases. The prognosis is generally considered to be poor, with a reported 10-year mortality rate of 9% to 61% . Moreover, the presentation of the tumor varies, so that the relationship of clinical risk factors and prognosis remains unclear.
The aim of the present study was to describe the 7-year experience of a tertiary medical center with insular thyroid carcinoma.
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Patients and methods
The study group consisted of 17 patients with a histologic diagnosis of insular thyroid carcinoma ( Figs. 1–3 ), based on the WHO classification , who attended the Department of Otolaryngology, Head and Neck surgery of Rabin Medical Center, Israel, in 1992–2009. Their files were reviewed for background data, clinicopathologic characteristics of the tumor, treatment, and outcome.
2
Patients and methods
The study group consisted of 17 patients with a histologic diagnosis of insular thyroid carcinoma ( Figs. 1–3 ), based on the WHO classification , who attended the Department of Otolaryngology, Head and Neck surgery of Rabin Medical Center, Israel, in 1992–2009. Their files were reviewed for background data, clinicopathologic characteristics of the tumor, treatment, and outcome.
3
Results
The 17 patients included 10 men and 7 women with a mean age 63 years at diagnosis (16–78). Mean tumor size was 3.7 ± 2.2 cm. None had a history of radiation exposure. Most were euthyroid at presentation. Preoperative fine-needle aspiration (FNA) study demonstrated papillary carcinoma in 11 patients (Bethesda 6), suspicious neoplastic cells in 5 patients (Bethesda 4), and a hyperplastic nodule in 1 patient (Bethesda 3). Five patients had enlarged lymph nodes, either clinically or on neck ultrasonography. Initial treatment in all cases consisted of total thyroidectomy, either in one session ( n = 9) or in two separate procedures ( n = 8), followed by radioiodine ablation. In addition, five patients received external beam radiation and one patient received chemotherapy. Of the 17 patients, 9 had extrathyroidal extension, 7 vascular invasion, 4 multifocal disease, and 4 distant metastases. Seven patients had positive pathologic lymph nodes at levels 2, 3 and 6. The final pathologic result was insular thyroid carcinoma in all 17 patients.
The mean duration of follow-up was 7 years with ranges from 6 months to 12 years and consisted of serial ultrasonographic examinations and measurement of thyroglobulin levels. At present, 11 patients are alive and well, 5 died of the disease, most of distant metastases, and 1 died of other causes. The overall 5-year survival was 83%.
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