INTRODUCTION Fibroblastic/myofibroblastic tumors constitute 12% of all pediatric soft tissue tumors with the majority of them belonging to the benign and intermediate prognostic categories. They are often misdiagnosed owing to their variable clinical presentation and unusual microscopic features. The diagnosis, specially cytological diagnosis of benign and intermediate categories is difficult due to paucity of cellular component and increased amount of extracellular matrix as compared to malignant ones. We hereby discuss the Fine needle aspiration cytology (FNAC) findings of non-malignant fibroblastic/myofibroblastic lesion in the pediatric age group encountered at our institute. METHODS All the benign and intermediate fibroblastic/myofibroblastic/fibroadipocytic lesions (age 0-12 years) diagnosed on FNAC over a period of 3½ years (Jan 2016- July 2019), with availability of corresponding histopathology were included in the study. RESULTS A total of seven pediatric benign and intermediate fibroblastic/myofibroblastic lesions with histopathological confirmation were identified which included Infantile digital fibromatosis (IDF) (n = 2), Lipofibromatosis (n = 1), Fibrous hamartoma of infancy (FHI) (n = 1), Fibromatosis colli (FC) (n = 2) and myofibroma/myofibromatosis (n = 1). FNAC smears were mainly paucicellular with presence of benign spindle shaped cells in a collagenous stroma common to almost all the cases. A few additional findings such as degenerated skeletal muscle fibres, muscle giant cells and mature adipose tissue were also present in some cases. CONCLUSION Fibroblastic/myofibroblastic tumors although uncommon, form an important category that must be considered in the differential diagnosis of pediatric soft tissue tumors. FNAC cytology features when assessed in a proper clinical setting (specially the age and site of presentation) are helpful in suggesting probable preoperative diagnosis in these lesions.

中文翻译：

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小儿年龄组的非恶性纤维母细胞/肌成纤维细胞肿瘤：细胞学诊断的线索和陷阱。

简介纤维母细胞/肌纤维母细胞瘤占所有儿科软组织肿瘤的12％，其中大多数属于良性和中度预后类别。由于其可变的临床表现和不寻常的微观特征，它们常常被误诊。由于细胞成分的缺乏和与恶性细胞相比的细胞外基质的增加，诊断，特别是良性和中间性类别的细胞学诊断是困难的。我们在此讨论在我们研究所遇到的小儿年龄组的非恶性成纤维细胞/肌成纤维细胞病变的细针穿刺细胞学检查（FNAC）的发现。方法这项研究包括在FNAC上经3.5年（2016年1月至2019年7月）诊断的所有良性和中性纤维母细胞/肌纤维母细胞/纤维脂肪细胞性病变（0-12岁），并提供了相应的组织病理学资料。结果共鉴定出7例经组织病理学证实的小儿良性和中性纤维母细胞/肌纤维母细胞病变，包括小儿数字化纤维瘤病（IDF）（n = 2），脂肪纤维瘤病（n = 1），婴儿纤维状错构瘤（FHI）（n = 1 ），结肠纤维瘤病（FC）（n = 2）和肌纤维瘤/肌纤维瘤病（n = 1）。FNAC涂片主要是少突性细胞，在几乎所有情况下常见的胶原基质中均存在良性纺锤状细胞。其他一些发现，例如骨骼肌纤维变性，在某些情况下还存在肌肉巨细胞和成熟的脂肪组织。结论纤维母细胞/肌纤维母细胞瘤虽然不常见，但却是鉴别小儿软组织肿瘤时必须考虑的重要类别。在适当的临床环境（特别是年龄和出现部位）中进行评估时，FNAC细胞学特征有助于提示可能在这些病变中进行术前诊断。