What is the significance of a spongiform hypoechoic thyroid nodule?

From the Guidelines

A spongiform hypoechoic thyroid nodule is generally considered a benign finding that typically does not require immediate intervention, as supported by the most recent evidence from 1. These nodules are characterized by their sponge-like appearance on ultrasound, containing multiple small cystic spaces within a predominantly solid nodule. The management approach is primarily observation with periodic ultrasound monitoring every 1-2 years to ensure stability in size and characteristics. Some key points to consider in the management of spongiform hypoechoic thyroid nodules include:

• Fine needle aspiration (FNA) biopsy is usually not necessary for purely spongiform nodules unless they are larger than 2 cm, show suspicious features, or demonstrate significant growth during follow-up, as recommended by 1.
• The benign nature of these nodules is supported by their distinctive ultrasound appearance, which has a high positive predictive value for benignity (over 99%).
• Patients with spongiform nodules should have thyroid function tests to rule out functional abnormalities, as suggested by 1.
• If the nodule causes compressive symptoms like difficulty swallowing or breathing, or if it grows significantly, further evaluation may be warranted. Some important considerations in the diagnosis and management of thyroid nodules include:
• The use of ultrasound features associated with malignancy, such as hypoechogenicity, microcalcifications, and irregular borders, to guide the decision for FNA biopsy, as discussed in 1.
• The role of molecular testing for thyroid nodules, including BRAF, RAS, RET/PTC, and PAX8/PPARγ mutations, in identifying nodules with a high risk of malignancy, as reported in 1.
• The importance of coordinated guidelines for the management of small thyroid nodules, as highlighted in 1. Overall, the management of spongiform hypoechoic thyroid nodules should prioritize a conservative approach with periodic monitoring, reserving more invasive procedures for nodules with suspicious features or significant growth, as supported by the most recent evidence from 1 and 1.

From the Research

Spongiform Hypoechoic Thyroid Nodule Characteristics

• Spongiform nodules are usually benign, with a low risk of malignancy 2, 3, 4
• Ultrasonography features related to malignancy, such as microcalcification, taller than wide shape, and marked central blood flow, are rare in spongiform nodules 2
• The presence of a spongiform or cystic appearance on ultrasound suggests a benign process that does not require additional testing 3, 4

Diagnosis and Management

• Fine-needle aspiration biopsy (FNA) is the standard test to determine whether surgical removal of a detected nodule is recommended 5, 6
• FNA has an essential role in the evaluation of patients with thyroid nodules to reduce the rate of unnecessary thyroid surgery for patients with benign nodules and triage patients with thyroid cancer to appropriate surgery 5
• Ultrasound-guided biopsy of nodules with suspicious imaging features is the best tool for risk stratification for malignancy in thyroid nodules 4
• The American Thyroid Association recommends FNA biopsy for evaluation of spongiform nodules ≥20 mm or observation without FNA, although this is a weak recommendation supported by moderate quality evidence 2

Risk Stratification

• High-resolution US is the most sensitive, easily available, and cost-effective diagnostic test available to detect thyroid nodules, measure their dimensions, and identify their structure 4
• The presence of calcifications, irregular spiculated outline, hypoechogenicity in a solid nodule, chaotic intranodular vascularity, and an elongated shape are well-known US features of malignancy in thyroid nodules 4
• Spongiform nodules, purely or predominantly cystic nodules, nodules with well-defined hypoechoic halo, and echogenic as well as isoechoic nodules are usually benign 4