Histiocytic sarcoma (HS) is a malignant neoplasm of hematopoietic origin. It is an exceedingly rare and aggressive malignancy commonly seen in adults. Diagnosis is difficult owing to lack of specific clinical manifestations with the absence of precursor lesions or causative agents. Hence, it primarily relies on histopathological morphology combined with immunohistochemistry, which is time-consuming, hence resulting in delayed treatment. However, diagnostic utility of flow cytometry is not well established in this. We report a case of a 45-year-old man who presented with right axillary lymphadenopathy for 1 month. FNAC was performed on the axillary lymph node, which showed large, atypical lymphoid/histiocyte-like cells. On flow cytometry, these cells were CD64+, CD11c+, and CD45+ suggesting histiocytic sarcoma. Similar morphology was seen on incisional biopsy. On immunohistochemistry, the cells were negative for B and T cell markers, PAX5, EMA, CK, ALK, and CD1a and expressed CD68, S100, and CD11c. A diagnosis of histiocytic sarcoma was made. Hence, flow cytometry can be a highly effective and powerful tool for the early detection of HS and can help in prompt treatment, given its aggressive clinical course and low survival interval.

中文翻译：

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流式细胞术在识别组织细胞肉瘤中的诊断效用——病例报告

组织细胞肉瘤（HS）是一种起源于造血系统的恶性肿瘤。这是一种极为罕见的侵袭性恶性肿瘤，常见于成人。由于缺乏特定的临床表现，没有前驱病变或病原体，诊断很困难。因此，它主要依赖于组织病理学形态结合免疫组织化学，这很耗时，因此导致治疗延迟。然而，流式细胞术的诊断效用在这方面并没有得到很好的确立。我们报告了一例 45 岁男性，他因右侧腋窝淋巴结肿大 1 个月就诊。对腋窝淋巴结进行 FNAC，显示大的非典型淋巴样/组织细胞样细胞。在流式细胞仪上，这些细胞是 CD64+、CD11c+ 和 CD45+，提示组织细胞肉瘤。切口活检可见类似形态。在免疫组织化学上，这些细胞对 B 和 T 细胞标志物 PAX5、EMA、CK、ALK 和 CD1a 呈阴性，并表达 CD68、S100 和 CD11c。诊断为组织细胞肉瘤。因此，流式细胞术可以成为早期检测 HS 的高效和强大的工具，并且可以帮助及时治疗，因为它具有侵略性的临床过程和低生存期。