Primitive myxoid mesenchymal tumor of infancy (PMMTI) is a recently described entity, previously included under the umbrella of undifferentiated sarcomas. These tumors are notorious for recurrence, chemoresistance and may even metastasize. We describe here, for the first time, the cytomorphology of PMMTI. Further, we discuss the morphological differentials and relevant immunocytochemical markers to reach a correct diagnosis. Knowledge about the distinctive cytomorphological features with characteristic immunocytochemistry is the key to the challenging diagnosis of PMMTI. Establishing the diagnosis on cytology is not difficult in cases of recurrence when such a history is forthcoming. These tumors are a rarity, and awareness of cytomorphology and employment of ancillary techniques is diagnostic, guiding the appropriate therapeutic management.

中文翻译：

---

婴儿原始粘液样间充质瘤的细针穿刺细胞学检查

婴儿原始粘液样间充质瘤 (PMMTI) 是最近描述的实体，以前被归入未分化肉瘤的范畴。这些肿瘤因复发、化学抗性甚至可能转移而臭名昭著。我们在这里首次描述了 PMMTI 的细胞形态学。此外，我们还讨论了形态学差异和相关的免疫细胞化学标记物，以做出正确的诊断。了解具有特征性免疫细胞化学的独特细胞形态学特征是 PMMTI 具有挑战性诊断的关键。当出现此类病史时，在复发病例中建立细胞学诊断并不困难。这些肿瘤很少见，对细胞形态学的认识和辅助技术的使用具有诊断意义，可指导适当的治疗管理。