Ultrasonographic Microcalcifications in Metastatic Lymph Nodes of Papillary Thyroid Carcinoma: A Sonopathological...

Background/Objectives: Ultrasonographic microcalcifications are highly specific imaging features of malignancy in both thyroid nodules and metastatic cervical lymph nodes in papillary thyroid carcinoma (PTC). However, although their histopathological correlates in thyroid nodules have been extensively investigated, the pathological substrates underlying microcalcifications in metastatic lymph nodes remain poorly defined, particularly for ultrasound-based diagnostic interpretation. Methods: This retrospective sonopathological cohort study included 32 patients with PTC, contributing 70 metastatic cervical lymph nodes. Lymph nodes were classified based on the presence or absence of microcalcifications detected by ultrasonography. Histopathological features-psammoma bodies, hyalinization, stromal calcification, cystic degeneration, and papillary formation-were systematically re-evaluated by pathologists blinded to ultrasonographic findings using a predefined semi-quantitative grading protocol. Microcalcification-positive metastatic lymph nodes were additionally compared with a reference cohort of microcalcification-positive thyroid nodules (n = 30). Results: Ultrasonographic microcalcifications were identified in 30 of 70 metastatic lymph nodes (42.9%). Microcalcification-positive lymph nodes demonstrated significantly higher frequencies of psammoma bodies (56.7% vs. 17.5%, p = 0.001), moderate-to-extensive psammoma bodies (40.0% vs. 12.5%, p = 0.003), stromal calcification (30.0% vs. 0.0%, p < 0.001), and cystic degeneration (80.0% vs. 12.5%, p < 0.001) compared with microcalcification-negative nodes. Notably, 43.3% of microcalcification-positive nodes lacked moderate-to-extensive psammoma bodies, indicating heterogeneous pathological correlates. Comparative analysis revealed no significant differences between microcalcification-positive nodes and thyroid nodules in the prevalence or extent of psammoma bodies or stromal calcification; however, hyalinization was significantly more frequent and extensive in thyroid nodules (both p < 0.001). Conclusions: Ultrasonographic microcalcifications in metastatic lymph nodes of PTC reflect heterogeneous histopathological correlates beyond psammoma bodies alone. These findings highlight the importance of anatomically informed, context-specific interpretation of microcalcifications in ultrasound-based diagnostic practice.