What is the next step in managing a patient with a multinodular thyroid goiter and bilateral lesions?

Management of Multinodular Thyroid Goiter with Bilateral Lesions

Fine-needle aspiration (FNA) biopsy should be performed on the left thyroid lobe nodule measuring 2.2 x 2.1 x 1.7cm as the next step in management. 1, 2

Rationale for FNA Biopsy

The patient presents with multinodular thyroid goiter with multiple bilateral lesions of varying sizes. Based on current guidelines, the decision to perform FNA is guided by nodule size and ultrasound characteristics:

• The left thyroid lobe contains a hypoechoic solid/cystic nodule measuring 2.2 x 2.1 x 1.7cm, which exceeds the 1cm threshold recommended for FNA by multiple guidelines 1, 2
• The American Thyroid Association and National Comprehensive Cancer Network recommend FNA for any thyroid nodule >1cm 2
• The right thyroid lobe nodule measuring 1.4 x 1.4 x 0.9cm also meets size criteria for FNA, but priority should be given to the larger left nodule 2

Selection of Nodules for FNA

When dealing with multinodular goiter, not all nodules require biopsy. The approach should be:

1. Target the largest nodule (in this case, the 2.2cm left lobe nodule)
2. Target any nodules with suspicious ultrasound features (if present)
3. Consider biopsy of additional nodules >1cm if they have different sonographic appearances 1, 2

Laboratory Testing to Consider

In addition to FNA, the following laboratory tests should be ordered:

• Serum TSH to assess thyroid function 3
• Free T4 and T3 if TSH is abnormal 2
• Consider serum calcitonin to rule out medullary thyroid cancer (higher sensitivity than FNA) 2

Imaging Considerations

• Radioisotope scanning is generally not helpful in determining malignancy in euthyroid patients with multinodular goiter 1
• If the patient has symptoms of hyperthyroidism or a suppressed TSH, a radioactive iodine uptake scan may be indicated to identify hyperfunctioning nodules 1, 2
• CT imaging should be considered only if there are concerns about substernal extension or tracheal compression 1

Potential Pitfalls and Caveats

1. Avoid the "watch and wait" approach for nodules >1cm: While some guidelines suggest observation for nodules <1cm, the left lobe nodule (2.2cm) clearly warrants FNA 2, 3

2. Don't rely on radioisotope scanning alone: In euthyroid patients, cold nodules have low positive predictive value for malignancy 1

3. Don't assume benignity in multinodular goiter: Malignancy is just as common in multinodular goiter as in solitary nodules 4

4. Avoid incomplete evaluation: Even if one nodule is biopsied and found benign, other suspicious nodules may still require evaluation 2

Follow-up Management Based on FNA Results

The subsequent management will depend on the FNA results:

• Malignant cytology: Refer for surgery (total or near-total thyroidectomy) 2, 4
• Suspicious/indeterminate cytology: Consider surgery unless autonomous function can be confirmed by scintigraphy 3
• Benign cytology with large symptomatic goiter: Consider surgery for alleviation of symptoms 3
• Benign cytology without symptoms: Observation with periodic follow-up including neck palpation and ultrasound examination 3

In conclusion, given the size of the left thyroid lobe nodule (2.2cm) and the presence of multiple bilateral nodules, FNA biopsy of the largest nodule is the appropriate next step in management, along with thyroid function tests to guide further decision-making.