A Practical Diagnostic Approach to Solid/Trabecular Nodules in the Thyroid

Nodules having a non-follicular–non-papillary structure may be frequently encountered in the thyroid, the solid/trabecular arrangement being the most common feature. When solid/trabecular pattern is predominant within a thyroid nodule, the wide range of differential diagnoses represents one of the major diagnostic problems in the routine thyroid practice, including – among others – relatively frequent entities such as trabecular adenoma or solid variant of papillary carcinoma and rare tumors such as hyalinizing trabecular tumor or paraganglioma. Morphology alone may not be sufficient to proper-type solid/trabecular tumors in the thyroid and, therefore, a panel of immunohistochemical markers is recommended, including thyroglobulin/calcitonin as the first step, followed by specific markers according to the morphological and clinical setting. A schematic algorithm is presented, which takes into consideration the diagnostic hallmarks of the most relevant entities that enter in the differential diagnosis in solid/trabecular nodules within the thyroid.