Eggshell Calcifications at Thyroid Ultrasound: A Sample-focused Analysis of Cytological Findings and Post-thyroidectomy Pathological Correlates

Abstract

Eggshell calcifications at thyroid ultrasound are connected to the challenging field of thyroid nodules and/or malignancy from a multidisciplinary perspective. Calcifications may be found in malignant and benign tumors; typically, micro-calcifications are identified in the papillary type of cancer, being equivalent to psammoma bodies in the pathological report. The risk of macro-calcifications, however, is more nuanced; recent data suggest a potential connection with a differentiated malignancy as well. Eggshell calcifications, a distinct type of macro-calcification, are generally considered benign findings, especially uninterrupted forms. Yet, the real incidence is not clear, which is why the topic remains open. In this narrative review, we analyzed eggshell calcifications in relationship with cytological diagnosis upon fine needle aspiration and post-thyroidectomy histological report. A PubMed-based search of the English-language papers using several keywords identified 171 articles. We only included original studies (no timeline restriction). After removing duplicates and applying the inclusion and exclusion criteria, 14 original studies were analyzed. The number of subjects per study varied (N=61 to 2678) so did the number of analyzed nodules per study (a maximum of 2902). Some studies found connections with benign features; others revealed a higher risk of malignancy at fine needle aspiration. Data remain heterogeneous, and oftentimes, studies investigated it only as a secondary endpoint. A high TI-RADS score is important in malignancy prediction, while eggshell calcification might add to the positive predictive value, yet, this trait is difficult to classify as a standalone element. Nevertheless, an interrupted pattern does not exclude thyroid cancer.