Follicular thyroid carcinoma (FTC) is a malignant form of thyroid tumor that originates in the follicular cells of the thyroid. This form of thyroid carcinoma is considered the second most common thyroid cancer, with the frequency of approximately 15% of all thyroid cancers, after papillary thyroid carcinoma. The exact cause of thyroid cancers including FTC is unknown; however, thyroid cancers are found more often in patients with previous history of exposure to external radiation as well as in those with family history of thyroid diseases. Usually, FTC occurs in individuals of ages between 15 and 84 years, and it is less common in children. FTC may invade neighbor tissues and spread easily to other organs. Vascular invasion is a distinguishing feature for FTC, therefore, distant metastases are common. Noticeably, about 10-15% of patients with FTC have lung and bone metastases. Involvement of lymph nodes in FTC is less common in FTC (8-13%) than in some other thyroid cancers.
Mortality depends mainly upon the degree of vascular invasion with a rate of 1.5% in females and 1.4% in males. However, FTC and almost all thyroid cancers are curable. Caucasians and women are more affected with FTC than Blacks and men, respectively. Relative incidence of follicular carcinoma is higher in areas of endemic goiter.
Al-Alawi and Abdul Fattah (1998) described an 85 years old man with a 12 years history of slowly increasing neck swelling progressing dysphagia to solid food and hoarseness of voice over the last 12 years. On examination, a huge multinodular swelling in the neck was detected that was more remarkable on the right side. CT scan showed huge thyroid mass with extensive cervical lymphadenopathy; direct compression of the trachea, esophagus and vertebral bodies; and extension into the superior mediastinum and floor of the mouth. There was no vascular dissemination. The patient died shortly after admission due to cardio-respiratory failure.
[Al-Alawi AH, Abdul Fattah MM. A rare case of follicular thyroid carcinoma. J Bahrain Med Soc. 1998; 10(1):45-6.]
Shomaf et al. (2006) investigated the trends in presentation and distribution of differentiated thyroid cancer at the largest referral hospital for endocrine cancers in Central Jordan. They analyzed the clinical features, management and outcome of 110 patients diagnosed with thyroid carcinoma at Jordan University Hospital, Amman, between 1996 and 2001. Papillary carcinoma was diagnosed in 87 patients (80%), follicular carcinoma in 3 patients (2.7%), Hurthle cell carcinoma in 8 patients (7.3%), medullary carcinoma in 5 (4.5%), and anaplastic carcinoma in 4 patients (3.6%), metastatic cancer in 2 patients and lymphoma in one patient. All patients with follicular carcinoma were diagnosed in the period 1986-1994. After thyroidectomy and a follow up period of 2-15 years, 10 patients died of their disease, 4 of these died within one year from anaplastic thyroid carcinoma. Shomaf et al. (2006) concluded that the dramatic decline in the incidence of follicular thyroid carcinoma combined with the increase in the advanced forms of thyroid cancer in Central Jordan may suggest a possible environmental factor in thyroid carcinogenesis in this region.
Ghfir et al. (2005) reported an 82-year-old woman with follicular thyroid carcinoma that metastasized to unusual skin locations. She was followed after a total thyroidectomy for follicular thyroid carcinoma. Assessment after 2 years showed the presence of a small cervical residue, pulmonary metastases, and a high thyroglobulin level. Two sets of internal radiation therapy with iodine 131 (100 mCi each) followed. Response to treatment was poor, and cutaneous and subcutaneous nodules appeared on the abdomen, back, and front left thigh. Biopsy of these lesions showed that they were malignant, and testing with anti-thyroglobulin antibodies confirmed the diagnosis of cutaneous metastasis of follicular thyroid carcinoma.
Chtourou et al. (2006) reported the case of a 66-year-old man treated in 1992 for follicular thyroid carcinoma and hospitalized in 1995 for a pink vascularized mass in the iris. At that time, neither local recurrence nor metastasis in other organs was observed. Histopathologic findings were typical of follicular thyroid metastasis carcinoma. The patient had refused adjuvant treatment but was followed up for 23 months after the diagnosis of the iris metastasis.
Saadi et al. (2001) conducted a retrospective review and identified 61 patients diagnosed with intrathyroidal well-differentiated FTC between 1958 and 1991. Median age at diagnosis was 42 years (range, 15-78 years). Most patients (90.2%) had a lobectomy or subtotal thyroidectomy. Median tumor size was 3.0 cm (range, 0.9-9.5 cm). Fifty-eight patients (95.1%) received thyroid hormone supplementation, and 5 (8.2%) received radioactive iodine ablation postoperatively. Median follow-up was 11 years (range, 3-35 years). Local recurrence, metastasis, or both developed in 3 patients (4.9%), and all subsequently died of thyroid cancer. The cumulative 10- and 15-year cancer-specific survival rate was 96.5%. Factors significantly related to worse survival were oxyphilic histology (log-rank, P =.00) and tumor size of more than 4 cm (P =.001). However, neither was found to be an independent predictor of outcome by Cox multivariate analyses (P =.7 and.9, respectively). The extent of initial operation (unilateral versus bilateral procedure) was not significantly related to survival (P =.52).