Diagnostic Pitfalls in Fine-Needle Aspiration of Metastatic Carotid Body Paraganglioma: A Case Report

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We report a case of a metastatic carotid body tumor. At the time of the biopsy and during initial review of the fine-needle aspiration sample, the remote history of carotid body tumor was unknown to the clinician and the cytopathologist. Fine-needle aspiration smears showed morphology suggestive of endocrine features such as lack of cohesion, manifesting as tumor cells seen mostly as single intact cells with “salt-and-pepper”–type chromatin, intranuclear inclusions, eccentrically placed nuclei lacking prominent nucleoli, and moderately abundant cytoplasm. Occasional significantly larger tumor cells were noted as well. Included in the differential diagnosis was well-differentiated adenocarcinoma, such as lung cancer, thyroid papillary carcinoma, thyroid medullary carcinoma, and various neuroendocrine tumors. Immunohistochemistry on cell block confirmed neuroendocrine differentiation. Knowledge of the patient’s history of carotid body tumor was crucial to the accurate diagnosis in this case, as morphologic features alone are typically not sufficient to distinguish benign from malignant carotid body tumors, or other neuroendocrine lesions. The tumor was determined to be malignant based on the history of the primary carotid body tumor, with the same morphologic features as seen in the previous specimen, combined with the location of the current tumor away from the primary tumor site. Our case demonstrates the importance of accurate and complete clinical history, consideration of pertinent morphologic findings, and collection of material for cell block allowing for appropriate immunohistochemical staining.

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