A 28-year-old white woman saw her primary care practitioner after she felt a lump on her neck – she had never felt it before. She had not experienced any neck pain, difficulty swallowing or breathing, or voice changes and has never had radiation to her head or neck. Her family history is positive for a maternal cousin with Graves’ disease and a maternal aunt with thyroid problems.
A TSH was ordered and was 0.99 uIU/mL (normal range 0.36-4.57). A neck ultrasound indicated a heterogeneous 2.6 × 1.3 × 1.5 cm nodule appearing within the left thyroid lobe. Internal flow was noted with the presence of microcalcifications – no other masses were present. FNA (fine needle aspiration) biopsy was then performed which noted numerous papillary groups and many cells with nuclear grooves and intranuclear inclusions, diagnostic of papillary thyroid cancer (PTC). A pre-operative ultrasound was performed to evaluate for lymphadenopathy which was negative.
The patient underwent a total thyroidectomy with the final pathology revealing a 3.5 cm left papillary carcinoma, with focal extrathyroidal extension. Two lymph nodes were negative for carcinoma and no lymph-vascular invasion was seen. TNM assessment was performed and the patient was noted to be T2N0M0. Since she is < 45 years of age, she had stage I papillary thyroid cancer. A thyroglobulin was drawn and was less than 0.5 ng/mL and a urine pregnancy test was negative. She was then given 131 mCi of I-131 by mouth and instructed to start taking levothyroxine.
Thyroid nodules are very common with the majority (95%) of thyroid nodules benign. FNA biopsy should be performed on any nodule > 1 cm to evaluate for malignancy. Any nodule, regardless of size, with ultrasound features suspicious for malignancy (e.g. microcalcifications, hypoechoic, increased vascularity, infiltrative margins, or nodule being taller than wide on transverse view) should be biopsied.
PTC is the most common and most treatable type of thyroid cancer – it occurs at any age and is the fifth most common cancer in women – the prognosis is excellent. Lymph node metastasis is not uncommon. While a history of radiation exposure is one risk factor for PTC – this can be from a childhood exposure (treatment of acne, enlarged tonsils or treatment for lymphoma), medical therapy (treatment of cancer), or environmental exposure – family history of thyroid cancer is another.
Total thyroidectomy is the standard of care for PTC. Since lymph node metastasis is seen in some newly diagnosed patients with PTC, a neck ultrasound is often performed prior to surgery to evaluate for suspicious lymph nodes.
Risks of surgery include bleeding, hoarseness due to injury to the recurrent laryngeal nerve, and hypocalcemia due to injury of the parathyroid glands.
Patients with PTC are followed long term by their endocrine surgeon and endocrinologist. The endocrinologist prescribes radioactive iodine ablation (I 131) for the majority of patients with PTC – though I 131 is not always necessary, especially for cancers that are unifocal and less than 1 cm. The purpose of I 131 following surgery is to ablate any remaining thyroid tissue, decrease recurrence, and facilitate monitoring of the cancer long term with a tumor marker for PTC called Thyroglobulin. Chemotherapy and radiation are rarely used to treat PTC.
Levothyroxine is used as thyroid hormone replacement following surgery but also as a thyroid cancer suppressor.
Revised American Thyroid Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer, November 2009