Department of Pathology, Fudan University Zhongshan Hospital, 180 Fenglin Road, Shanghai, 200032, China.
Diagn Pathol. 2023 Feb 10;18(1):17. doi: 10.1186/s13000-023-01301-3.
Systemic mastocytosis (SM), a rare myeloid neoplasm, is defined as a clonal and neoplastic proliferation of mast cells in at least one extracutaneous organ(s). The pathologic diagnosis and treatment of SM are challenging.
We presented a 44-year-old male patient who had endured abdomen discomfort for 4 years and diarrhea for 5 months. Colonoscopy and PET/CT found a protuberant lesion in the cecum with adjacent lymphadenopathy. Histopathology of the cecum biopsy showed diffuse infiltration of medium-sized round/oval cells in lamina propria with immunohistochemical expressions of CD45, CD117, CD25, CD68, CD123, CD56, CD4, and CD35, mimicking blastic plasmacytoid dendritic cell neoplasm. Sanger sequencing revealed missense mutation (D816V) in the exon 17 of KIT gene. Serum tryptase level was 38.56 ng/ml. No abnormality was found in skin examination and bone marrow biopsy. No primitive cells were observed in bone marrow smear and peripheral blood smear. The diagnosis of aggressive SM with intestinal tract involvement was established. The patient received avapritinib treatment at an initial dosage of 200 mg once daily and exhibited dramatic clinical improvement but memory impairment within 1 month. No recurrence was observed in 1-year follow-up at the adjusted avapritinib dose (75 mg once daily).
SM is very rare and should be considered in patients with long-term diarrhea symptoms and hematopoietic/lymphoid-appearing tumors. KIT D816V mutation contributes to the differentiation of CD123, CD4, and CD56 immunoreactive SM from blastic plasmacytoid dendritic cell neoplasm. The rare side-effect of memory impairment in this case helps to accumulate the experience of avapritinib in treating KIT D816V-mutant SM.
系统性肥大细胞增多症（SM）是一种罕见的髓系肿瘤，定义为至少一个皮肤外器官中肥大细胞的克隆性和肿瘤性增殖。SM 的病理诊断和治疗具有挑战性。
我们报告了一位 44 岁男性患者，他因腹部不适 4 年和腹泻 5 个月而就诊。结肠镜检查和 PET/CT 发现盲肠有一突起性病变，并伴有邻近淋巴结病。盲肠活检的组织病理学显示固有层弥漫性浸润中等大小的圆形/椭圆形细胞，免疫组化表达 CD45、CD117、CD25、CD68、CD123、CD56、CD4 和 CD35，类似于原始细胞样浆细胞样树突细胞肿瘤。Sanger 测序显示 KIT 基因外显子 17 中的错义突变（D816V）。血清类胰蛋白酶水平为 38.56ng/ml。皮肤检查和骨髓活检未见异常。骨髓涂片和外周血涂片未见原始细胞。诊断为侵袭性 SM 伴肠道受累。患者接受了阿伐普利尼治疗，起始剂量为 200mg 每日一次，治疗后 1 个月内临床症状明显改善，但出现记忆力减退。在调整后的阿伐普利尼剂量（75mg 每日一次）1 年随访时未见复发。
SM 非常罕见，对于有长期腹泻症状和造血/淋巴样肿瘤的患者应考虑 SM。KIT D816V 突变有助于区分 CD123、CD4 和 CD56 免疫反应性 SM 与原始细胞样浆细胞样树突细胞肿瘤。本例中罕见的记忆力减退的副作用有助于积累阿伐普利尼治疗 KIT D816V 突变 SM 的经验。
