Endocrine Abstracts

Objective: Ultrasonographic (US) echogenic micro-foci are frequently seen in papillary thyroid carcinoma (PTC). General belief is that microcalcifications represent psammoma bodies. But the subject is debatable and other sonographic intranodular echogenic figures can be seen in PTC. We aimed to examine the nonshadowing echogenic figures and their histopathological correlations in PTC.

Methods: We prospectively collected US video records of PTC cases with echogenic micro-foci or metastatic lymph nodes (MLN) and malignant nodules without echogenic foci between 2018 and 2021 in two centers. All video recordings were independently interpreted by three experienced sonographists. Non-shadowing echogenic micro-foci were classified as; microcalcification (punctate echogenic foci <1 mm), linear (>2 mm), comet-tail, coarse echogenic foci and unclassifiable. Histopathological evaluation was performed by two experienced pathologists. Data were evaluated by an investigator who is blind to these results.

Results: 92 nodules and 12 metastatic lymph nodes out of 160 patients, agreed on the type of echogenic foci by at least two of three sonographers, was included in the statistics. While 72 of 92 malignant nodules had any kind of echogenic micro-foci (group 1), 22 did not (group 2). According to histopathological evaluation, number of psammoma bodies, coarse stromal calcifications and papillae are significantly higher in group 1 than in group 2 [(76% vs 5%, P < 0.001), (38.6% vs 4.5%, P = 0.002), (87% vs 50% P = 0.001)]. Same parameters were significantly higher in nodules with microcalcifications than in nodules without echogenic foci [(85% vs 4.5%, P < 0.001), (29% vs 4.5%, P = 0.024), (85% vs 50%, P = 0.003)]. Coarse stromal calcifications and papillae are significantly higher in nodules with linear echogenic micro-foci than in nodules without echogenic foci [(57% vs 4.5%, P = 0.007), (100% vs 50%, P = 0.026)]. Most common histopathological findings in MLN with ecogenic foci were papillae (92%), psammoma (83%) and cystic areas (83%), respectively.

Conclusions: Punctate echogenic foci in PTC nodules indicate the presence of psammoma in pathology. Linear echogenic micro-foci are mostly associated with coarse stromal calcifications and papillae. Echogenic foci in metastatic lymph nodes may be associated with microcystic areas as well as psammoma and papillae.