Minimally Invasive Surgery of the Thyroid Workup

Updated: Nov 05, 2019
  • Author: Jagdish K Dhingra, MBBS, FRCS, FRCS(Edin), MS; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Workup

Laboratory Studies

Serum thyrotropin (TSH) is recommended for a thyroid nodule larger than 10-15 mm. [2]

Serum thyroglobulin and calcitonin are additional tests that can be performed if other thyroid conditions or medullary carcinoma of the thyroid (MCT) are suspected.

A full thyroid-function panel that includes TSH levels and free T3 and T4 levels can be performed if a clinical suspicion of hypothyroidism or hyperthyroidism exists.

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Imaging Studies

Thyroid ultrasonography (US) is the initial imaging modality of choice for suspicion of one or more thyroid nodules. [2]

CT, MRI, and positron emission tomography (PET) are adjunctive imaging modalities that can be used to assess cervical lymph node involvement for staging purposes. CT scanning and MRI can also reveal invasion of adjacent structures and airway compression and gauge the extent of substernal extension for large goiters.

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Other Tests

Radionuclide scanning (thyroid scintigraphy or iodine-131 uptake scan) can be used to diagnose an autonomously functioning or “hot” nodule. Lack of uptake or “cold” nodules have a malignant risk of 5-8%. [3]

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Diagnostic Procedures

Fine-needle aspiration (FNA) is the initial diagnostic procedure of choice. FNA can be performed under palpation or with US guidance. Nondiagnostic or inadequate FNA by palpation should be repeated with US guidance.

FNA is usually performed with a 27- or 25-gauge, 1.5-inch needle placed on a syringe. Once the needle has been inserted into the nodule, gentle suction is applied to the syringe; multiple passes are made within the nodule. Suction is then released prior to removing the needle from the nodule. The procedure is repeated 2-4 times and slides are prepared. Having a cytopathologist available for slide preparation to check on the adequacy of the sample is useful.

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Histologic Findings

FNA results, which are diagnostic, are most commonly benign. The most common benign diagnosis is a colloid nodule. [3]

Follicular neoplasms on FNA are hypercellular, low in colloid, and show microfollicular arrangement. Hürthle cell carcinoma is a variant of follicular carcinoma with a prominence of Hürthle cells.

The most frequent malignant lesion on FNA is papillary thyroid carcinoma (PTC). Histology shows tumor cells arranged in sheets, papillary cell groups, and nuclear abnormalities.

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Staging

The American Joint Committee on Cancer has devised the following staging system: [12]

  • Primary tumor (T)

    • TX: The primary tumor cannot be assessed.

    • T0: No evidence of a primary tumor is found.

    • T1: The tumor is 2 cm or less in its greatest dimension (limited to the thyroid).

    • T2: The tumor is larger than 2 cm but 4 cm or smaller in its greatest dimension (limited to the thyroid).

    • T3: The tumor is larger than 4 cm in its greatest dimension (limited to the thyroid), or a tumor with minimal extrathyroid extension is found (eg, extension to the sternothyroid muscle or perithyroid soft tissues).

    • T4a: A tumor of any size extends beyond the thyroid capsule to invade subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve.

    • T4b: A tumor invades prevertebral fascia or encases carotid artery or mediastinal vessels.

  • Regional lymph nodes (N)

    • NX: The regional lymph nodes cannot be assessed.

    • N0: No regional lymph node metastasis is found.

    • N1: Regional lymph node metastasis is found.

      • N1a: The metastasis has reached level VI (pretracheal, paratracheal, prelaryngeal/Delphian lymph nodes).

      • N1b: The metastasis has reached unilateral or bilateral cervical or superior mediastinal lymph nodes.

  • Distant metastasis (M)

    • MX: A distant metastasis cannot be assessed.

    • M0: No distant metastasis is found.

    • M1: A distant metastasis is found.

Papillary or follicular thyroid cancer staging is as follows:

  • Patients younger than 45 years

    • Stage I is any T, any N, and M0.

    • Stage II is any T, any N, and M1.

  • Patients aged 45 years or older

    • Stage I is T1, N0, and M0.

    • Stage II is T2, N0, and M0.

    • Stage III is one of the following:

      • T3, N0, and M0

      • T1, N1a, and M0

      • T2, N1a, and M0

      • T3, N1a, and M0

    • Stage IVA is one of the following:

      • T4a, N0, and M0

      • T4a, N1a, and M0

      • T1, N1b, and M0

      • T2, N1b, and M0

      • T3, N1b, and M0

      • T4a, N1b, and M0

    • Stage IVB is T4b, any N, and M0.

    • Stage IVC is any T, any N, and M1.

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