Cytologic findings of a clear cell parathyroid lesion

Abstract

On fine-needle aspiration (FNA) biopsy, clear cell parathyroid lesions can be misdiagnosed as thyroid neoplasms, salivary gland neoplasms, paraganglioma, or even metastatic renal cell carcinoma. We report the clinicopathological, cytologic, and histologic findings of a clear cell parathyroid tumor in a 64-year-old HIV-positive patient. A computed tomography (CT) scan with contrast showed a heterogeneous and enhancing mass at the inferolateral aspect of the left thyroid lobe. FNA showed a cellular smear with many single and loosely clustered tumor cells with finely granular and vacuolated light-purple cytoplasm and central nuclei. Occasional microfollicular structures were noted. No colloid was seen. This FNA was misdiagnosed as a follicular neoplasm of the thyroid. Sections of the excised mass showed large polyhedral cells with well-defined cell membranes and clear cytoplasm with a small amount of eosinophilic granular material. These clear cells were positive for pancytokeratin and PTH immunohistochemical stains. These results favored a diagnosis of parathyroid Water Clear Cell Adenoma. This brief report highlights the cytologic findings of clear cell parathyroid lesions and their potential diagnostic pitfalls.