Korean J Radiol.  2019 Jun;20(6):947-955. 10.3348/kjr.2018.0599.

Degenerating Thyroid Nodules: Ultrasound Diagnosis, Clinical Significance, and Management

• Ren J
• Baek JH
• Chung SR
• Choi YJ
• Jung CK
• Lee JH

• KMID: 2447073
• DOI: http://doi.org/10.3348/kjr.2018.0599

Abstract

Degenerating nodules (DNs), which primarily manifest as benign thyroid nodules, are one of the main causes of discordance in ultrasonography (US) and cytological assessments. Intranodular hemorrhage is one of the mechanisms contributing to discordant nodules, and an impaired blood supply may explain further DN shrinkage and infarction. The surgical specimens can be divided into acute and chronic stages based on the histological changes, which usually mimic the US features of malignant tumors. Serial US follow-up should be recommended instead of other unnecessary procedures. However, repeated fine-needle aspiration, diagnostic surgery, or core-needle biopsy may still be necessary for indeterminable or highly suspicious DNs.

Keyword

Thyroid nodules; Ultrasonography; Degenerating nodules; Fine-needle aspiration

MeSH Terms

Biopsy
Biopsy, Fine-Needle
Diagnosis*
Follow-Up Studies
Hemorrhage
Infarction
Thyroid Gland*
Thyroid Nodule*
Ultrasonography*
Unnecessary Procedures

Figure

• 

  Fig. 1 US features of degenerating nodule.Cystic portion is decreased and solid isoechoic portion (arrow, A) shows degeneration as isoechoic rim (arrow, B). US = ultrasonography

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  Fig. 2 Early-stage degenerating thyroid nodule.US image shows markedly hypoechoic solid nodule (A). Early stage of hemorrhage shows reddish gel-like material on FNA (B) and CNB (C). Consistency is like toothpaste (D). CNB = core-needle biopsy, FNA = fine-needle aspiration

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  Fig. 3 Second-stage degenerating thyroid nodule.US features of CNB (A) and CNB specimen (B) show brown semi-solid (bread-like) material (C) containing diffuse stromal fibrosis with chronic inflammation and deposition of histiocytes.

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  Fig. 4 Chronic-stage degenerating thyroid nodule.A. US image shows hypoechoic solid nodule with hyperechoic strip and acoustic shadow. B. Pathologic specimen shows dense stromal fibrosis with/without calcifications (HE, × 40). C. CNB shows whitish hard material. HE = hematoxylin and eosin stain

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  Fig. 5 Degeneration of cystic thyroid nodule.A. US image obtained in December 2007 showed that nodule was colloid cyst. B. In December 2010, nodule significantly collapsed. Degenerating nodule shows hypoechoic solid nodule with echogenic foci.

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  Fig. 6 Degeneration of solid thyroid nodule.A. US image showing that initial nodule was solid with inhomogeneous echogenicity. B. FNA was performed at this point. C, D. Three years later, nodule obviously collapsed. Power Doppler imaging revealed no vascular signal within nodule.

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  Fig. 7 Benign degenerating thyroid nodules from surgical specimen.A. Lesion has shrunk and shows fibrotic scarring with fibrinoid degeneration (HE, × 12). B. Follicular cells are paucicellular or virtually absent (HE, × 40). C. Well-circumscribed nodule shows cystic degeneration and calcification with peripheral fibrosis (HE, × 12). D. There are no atypical cells (HE, × 40). B and D are magnified views of A and C, respectively.

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  Fig. 8 CNB specimen of benign degenerating thyroid nodules (A, B) and PTC (C, D).Benign degenerating nodule shows no atypical cells (HE, × 40, A; HE, × 400, B). Paucicellular variant of PTC shows a few atypical follicular cells with typical nuclear features of PTC (HE, × 40, C; HE, × 400, D). PTC = papillary thyroid carcinoma

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