Individual case: Follicular thyroid cancer

A patient presented with sore throat, neck pain, trouble swallowing, and recent weight loss.


The patient

A 69-year-old man with a history of coronary artery disease presented with five days of sore throat, neck pain, and trouble swallowing. He described the throat pain as severe. He reported a recent 10-pound unintentional weight loss and night sweats. Upon presentation, his vital signs were unremarkable. His physical exam was notable for a hard, fixed left-sided neck mass but no lymphadenopathy. Examination of the mouth and pharynx were unremarkable. His bloodwork, including thyroid function testing, was within normal limits.

Figure 1 Chest X-ray demonstrating rightward tracheal deviation arrow as the result of mediastinal mass
Figure 1. Chest X-ray, demonstrating rightward tracheal deviation (arrow) as the result of mediastinal mass.
Figure 2 CT of the neck demonstrating a large mass in left thyroid lobe arrow and pathologic cervical lymphadenopathy
Figure 2. CT of the neck, demonstrating a large mass in left thyroid lobe (arrow) and pathologic cervical lymphadenopathy.
Figure 3 FNA pathological specimen at high power with Papanicolaou stain showing microfollicle formation long arrow and follicular cell nuclei overlapping with focal crowding wide arrow
Figure 3. FNA pathological specimen at high power, with Papanicolaou stain showing microfollicle formation (long arrow) and follicular cell nuclei overlapping with focal crowding (wide arrow).

IV dexamethasone was given, which improved his throat pain. A chest X-ray demonstrated focal rightward tracheal deviation (Figure 1). A CT of the neck showed a large left thyroid mass with pathological cervical lymphadenopathy (Figure 2). Thyroid ultrasound further characterized the thyroid mass as measuring approximately 6 × 4 × 5 cm, extending to the retrosternal intrathoracic region, and having mixed cystic and solid components. A thyroid fine-needle aspirate (FNA) biopsy was performed, which demonstrated follicular cell morphology (Figure 3). He underwent a successful swallow study and tolerated a diet. He was discharged with a steroid taper and outpatient follow-up for surgical resection.

The diagnosis

Thyroidectomy confirmed the diagnosis of follicular thyroid cancer (FTC). FTC is a malignancy of the thyroid follicular epithelial tract and is the second most common type of thyroid cancer (up to 12% of all thyroid cancer cases), after papillary thyroid cancer (up to 80% of cases). FTC has peak incidence between the ages 40 and 60 years in iodine-deficient areas. Iodine-deficient populations are at risk of developing goiter and thyroid nodules, which often precede development of thyroid cancer. FTC is three times more common in women than in men. Risk factors include history of radiation exposure during childhood and family history of thyroid cancer. Forty percent of patients with FTC have a point mutation of the RAS oncogene. PAX8-PPAR gamma is another gene that has been associated with follicular adenomas and cancer.

FNA biopsy is the most common initial diagnostic test but cannot always differentiate between a benign adenoma and follicular malignancy. A specific diagnosis of FTC requires histologic evaluation of the thyroid mass after surgery. Histology can provide insight into prognosis. Normal, well-differentiated epithelium with follicular development and colloid findings are associated with good prognosis, whereas poorly differentiated cells with solid growth and absence of follicles, marked nuclear atypia, and extensive vascular/capsular invasion are poor prognostic features. The 10-year survival rate is over 95% for patients younger than age 40 years with differentiated thyroid cancer and 80% in those ages 40 to 59 years. Between 10% and 15% of patients with FTC develop distant metastases, with lung and bone being common sites.

The primary therapy for FTC is surgical removal of the mass via total thyroidectomy. Postoperative management includes treatment with suppressive thyroid hormone therapy and radioiodine and monitoring for recurrence. Other less common treatment modalities, including external beam radiotherapy and chemotherapy, are typically reserved for nonresectable metastatic disease.

Pearls

  • FTC is the second most common type of thyroid cancer and is usually seen in patients of middle age and in iodine-deficient areas.
  • FNA biopsy is the most common initial diagnostic test for FTC but cannot differentiate between adenoma and cancer; specific diagnosis requires histologic evaluation of the thyroid mass after surgery.

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