Collision tumors, rare neoplasms underlying two distinct histological types of carcinomas (with different origins) separated by normal tissue, are described in many organs including the thyroid gland, but to a lesser extent. We aim to overview the current published data concerning collision tumors of the thyroid (CTT). This is a narrative review considering papers published on PubMed through a search starting from the terms “collision” and “thyroid”. Inclusion criteria are full-length articles, the English language, the timeline from inception to December 2022, and original studies with different levels of statistical evidence. We followed the main types of thyroid carcinomas: differentiated thyroid carcinoma of papillary and follicular type, anaplastic/ undifferentiated/poorly differentiated carcinoma, respectively medullary thyroid carcinoma. We identified 92 papers based on the mentioned
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
