Ultrasound patterns may help tell IgG4-positive Hashimoto’s thyroiditis apart from thyroid lymphoma

A small retrospective study suggests that ultrasound may help physicians distinguish IgG4-positive Hashimoto’s thyroiditis (IgG4-HT) from primary thyroid lymphoma (PTL), two conditions whose overlapping clinical and imaging features can lead to dangerous misdiagnosis. The pilot study, published in BMC Cancer, compared pathology-proven cases of both diseases and identified several sonographic features that appeared far more frequently in lymphoma patients.

The researchers analyzed 13 patients with IgG4-HT and 19 with PTL, all confirmed by histopathology. IgG4-HT is considered an aggressive subtype of Hashimoto’s thyroiditis that can mimic lymphoma, making reliable non-invasive differentiation clinically valuable. The two groups showed no significant differences in sex distribution, compressive symptoms, or thyroid function, but IgG4-HT patients were markedly younger, averaging 40.31 years compared with 69.00 years in the PTL group, a difference the authors reported as statistically significant.

The most striking differences emerged on ultrasound. Patients with PTL had substantially larger anterior-posterior thyroid diameters: 3.00 centimeters in the left lobe versus 1.65 centimeters in IgG4-HT, and 3.19 centimeters in the right lobe versus 1.62 centimeters, with both comparisons reaching statistical significance. Linear hyperechoic areas appeared in 89.5 percent of PTL cases but only 30.8 percent of IgG4-HT cases, and posterior acoustic enhancement was seen in 89.5 percent versus 15.4 percent of cases respectively.

Echogenicity itself proved highly discriminative. A very hypoechoic pattern, in which the thyroid tissue appears markedly darker than surrounding structures, was present in 78.9 percent of PTL patients and in none of the IgG4-HT patients. In addition, extrathyroidal extension, the spread of abnormal tissue beyond the thyroid capsule, was observed exclusively in the lymphoma group, appearing in 10.5 percent of those cases and never in IgG4-HT.

These findings point to a constellation of ultrasound signs, including marked anteroposterior enlargement, very hypoechoic echogenicity, and posterior acoustic enhancement, that may raise suspicion for PTL during initial evaluation. Because PTL requires prompt histopathological confirmation and treatment, recognizing these features early could help clinicians move more quickly toward biopsy rather than attributing findings to an atypical form of thyroiditis.

The authors emphasize that this was a pilot study with a limited sample size, and the reported associations come from a retrospective comparison of relatively small patient groups. The measurements carry uncertainty, as reflected in the reported standard deviations, and the diagnostic value of these ultrasound features has not yet been validated in larger or prospective cohorts. The study also cannot establish whether ultrasound alone is sufficient for diagnosis, only that it may contribute to earlier recognition and timely histopathological workup.

Subject of Research: Ultrasound differentiation of IgG4-positive Hashimoto's thyroiditis from primary thyroid lymphoma

Article Title: The role of ultrasound in distinguishing between IgG4‑positive Hashimoto’s thyroiditis and primary thyroid lymphoma: a pilot study

Article References: Zhang, Q., Wang, F., Chen, L., Chen, L., Gao, Y., Liu, L., & Zhao, C. (2026). The role of ultrasound in distinguishing between IgG4‑positive Hashimoto’s thyroiditis and primary thyroid lymphoma: a pilot study. BMC Cancer. https://doi.org/10.1186/s12885-026-16930-2

Image Credits: AI Generated

DOI: 10.1186/s12885-026-16930-2

Keywords: ultrasound, Hashimoto's thyroiditis, IgG4-related disease, primary thyroid lymphoma, thyroid imaging, retrospective study, pilot study, diagnostic imaging, BMC Cancer, sonographic features, role, distinguishing