Medullary thyroid carcinoma is a neuroendocrine tumor derived from parafollicular or ‘C’ cells with sporadic and familial forms. Fine needle aspiration cytology is a quick way to establish the diagnosis. Sometimes a usual tumor may show prominent spindling on cytomorphology due to sampling issues, which poses a diagnostic challenge. When encountering spindled tumor cells on cytology smears from the thyroid, differential diagnoses encompass many benign and malignant lesions. We present cytological findings of the usual type of medullary thyroid carcinoma showing extensive spindling on cytology smears, which was a diagnostic dilemma. An accurate diagnosis was reached with the judicious use of immunocytochemistry on the cell block. We also discuss the available literature, differential diagnoses, and how to troubleshoot.

中文翻译：

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甲状腺髓样癌的广泛纺锤体对诊断构成挑战：病例报告

甲状腺髓样癌是一种来源于滤泡旁或“C”细胞的神经内分泌肿瘤，具有散发性和家族性。细针抽吸细胞学检查是建立诊断的快速方法。有时，由于取样问题，常见的肿瘤可能会在细胞形态学上显示出明显的纺锤体，这对诊断提出了挑战。当在甲状腺细胞学涂片上遇到梭形肿瘤细胞时，鉴别诊断包括许多良性和恶性病变。我们提出了通常类型的甲状腺髓样癌的细胞学检查结果，在细胞学涂片上显示出广泛的纺锤体，这是一个诊断难题。在细胞块上明智地使用免疫细胞化学可以达到准确的诊断。我们还讨论了可用的文献、鉴别诊断以及如何排除故障。