The cytological features of granular cell tumour (GCT) are generally quite typical but, in some cases, the fine needle aspiration cytology (FNAC) diagnosis of GCT may be difficult or impossible because of unusual sites of onset or equivocal cytological features. In this report, two GCTs with atypical FNAC features are described in order to investigate the causes and provide possible diagnostic tips. From a series of nine histologically proven GCTs, two inconclusive FNAC cases were retrieved. Smears were poorly cellular showing isolated naked nuclei, anisonucleosis, granular chromatin and occasional small nucleoli. The background was finely granular in one case. Histological controls of these cases revealed marked fibrosis. Tumour‐associated fibrosis in GCT is variable and does not seem to influence clinical behaviour but it influences the harvest and the integrity of granular cells collected by FNAC. When GCT smears are poorly cellular, attention should be paid to the granular background and to the few granular cells, if any, as they might be the only features to suggest a GCT.

中文翻译：

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颗粒细胞瘤的非典型细胞学表现：肿瘤相关纤维化可能影响细针穿刺细胞学准确性

颗粒细胞瘤 (GCT) 的细胞学特征通常非常典型，但在某些情况下，GCT 的细针穿刺细胞学 (FNAC) 诊断可能很困难或不可能，因为发病部位不寻常或细胞学特征不明确。在本报告中，描述了两个具有非典型 FNAC 特征的 GCT，以调查原因并提供可能的诊断技巧。从一系列经组织学证实的九个 GCT 中，检索到两个不确定的 FNAC 病例。涂片细胞质量差，显示孤立的裸核、异核、颗粒状染色质和偶尔的小核仁。在一种情况下，背景是细粒度的。这些病例的组织学对照显示明显的纤维化。GCT 中的肿瘤相关纤维化是可变的，似乎不会影响临床行为，但会影响 FNAC 收集的颗粒细胞的收获和完整性。当 GCT 涂片细胞质量较差时，应注意颗粒背景和少数颗粒细胞（如果有），因为它们可能是提示 GCT 的唯一特征。