Objective: To investigate the clinicopathologic features, immunohistochemical phenotypes and biological behavior of pseudosarcomatous myofibroblastic proliferation (PMP) of the urinary bladder which may be misdiagnosed as a malignant neoplasm and undergo extensive treatment. Methods: Six cases of PMP of the urinary bladder were collected from 2001 to 2016 at Beijing Tiantan Hospital, Capital Medical University. The clinicopathologic features and immunophenotypic profile were studied by histopathological and immunohistochemical investigations with clinical follow-up. At the same time, the translocation of ALK gene was detected by fluorescence in situ hybridization (FISH). Immunohistochemistry was carried out using EnVision method for the expression of AE1/AE3, vimentin, EMA, SMA, Caldesmon, Calponin, desmin, ALK, Ki-67, MyoD1, myoglobin, CD34, S-100, CD117, CK7, CK20, GATA3, p63 and CK5/6. The related literature was reviewed. Results: There were two male and four female patients, significantly more common in women. The age of the patients was 27 to 53 years, and the median age was 35 years. The main clinical symptom was painless gross hematuria, one case with dysuria, and one case showed recurrent cystitis. There was no history of surgery and trauma. Follow-up ranged from 4 months to 13 years and showed five cases without recurrence and one case with recurrence. Microscopy showed submucosal lesion with inflammatory exudate and bleeding on the surface, in some cases extending to the superficial muscles of the bladder wall. The lesion was characterized by the proliferation of plump spindle cells, which were loose or dense in arrangement. There were varying degrees of acute and chronic inflammatory cells infiltration in the myxoid matrix. Spindle cells arranged in disorder, or a dense stranding, especially abundant in the cell region. The median mitotic rate was <2/10 HPF cells, but there were no pathological mitotic figures and without nuclear atypia in most spindle cells. Spindle cells with eosinophilic cytoplasm showed long tapering cytoplasmic projections. Oval or short spindle nuclei had vacuolization with prominent nucleoli, looking like ganglionic cells. There were scarce collagen fibers, and a few spindle cells degenerated with chromatin blurred. Some areas showed a granuloma-like pattern and neutrophils within vascular cavity. Immunohistochemically, the spindle cells were diffusely positive for vimentin, SMA and caldesmon. CKpan was strongly and diffusely positive. Desmin and calponin expression was varying. Ki-67 positive cells were about 35% to 55%, but the spindle cells were negative for myoglobin, S-100, CD117, CD34, p63 and CK5/6. FISH test showed that there was no ALK isolated signal in 6 cases of PMP, and so no positive cases were found. Conclusions: PMP of the urinary bladder is a benign non-neoplastic myofibroblastic proliferative lesion. Morphology is extremely easy to be misdiagnosed as malignant tumors, and therefore more attention should be paid to avoid this misdiagnosis.
目的： 探讨膀胱假肉瘤性肌纤维母细胞性增生(PMP)的临床病理学特点、免疫表型、鉴别诊断及生物学行为。 方法： 对北京天坛医院2001至2016年收集的6例膀胱PMP，采用EnVision法进行免疫组织化学标记，同时，应用荧光原位杂交(FISH)检测间变性淋巴瘤激酶(ALK)基因的易位情况。一抗选用广谱细胞角蛋白(CKpan)、波形蛋白、上皮细胞膜抗原(EMA)、平滑肌肌动蛋白(SMA)、Caldesmon、Calponin、结蛋白、ALK、Ki－67、肌调节蛋白(MyoD1)、肌红蛋白、CD34、S－100蛋白、CD117、细胞角蛋白(CK)7、CK20、GATA3、p63及CK5/6，进行光镜观察并结合免疫组织化学及FISH、临床表现特点综合分析其临床病理学形态及免疫表型特征，获得随访资料，并复习相关文献。 结果： 患者6例，男性2例，女性4例。年龄范围27～53岁，中位年龄35岁。主要临床症状为无痛性肉眼血尿，1例伴有排尿困难，1例表现为反复膀胱炎，均无手术及外伤史。随访4个月至13年，5例无复发，1例复发。光镜下病变位于黏膜下，部分区域延伸至膀胱壁浅肌层。表面为炎性渗出及出血。病变特征由增生的长而肥胖的梭形细胞构成，疏松或密集。间质疏松、水肿、黏液样，并有多少不等急慢性炎性细胞浸润。梭形细胞排列紊乱，也可呈致密条束状排列，特别在细胞丰富区域内。大多数梭形细胞无异型性，可见核分裂象(<2个/10 HPF)，但不见病理性核分裂象。梭形细胞胞质嗜酸性，可见长而逐渐变细的胞质突起。核呈卵圆形或短梭形，空泡状，有明显的核仁，似节细胞样细胞。其间胶原纤维稀少，少数梭形细胞核退变，染色质模糊不清。部分区域呈肉芽肿样图像，血管腔内可见中性粒细胞。免疫组织化学：梭形细胞均弥漫强阳性表达波形蛋白、SMA和Caldesmon，强阳性表达CKpan，不同程度表达结蛋白和Calponin，Ki－67阳性细胞约35%～55%，但不表达ALK、EMA、肌红蛋白、S－100蛋白、p63及CK5/6等。FISH检测显示本组6例PMP中均不存在ALK分离信号，未检出阳性病例，均为阴性。 结论： 膀胱PMP为一种良性非肿瘤性病变，肌纤维母细胞增殖，形态学极易误诊为恶性肿瘤，要避免误诊。.
Keywords: Diagnosis, differential; Immunophenotyping; Myofibroblasts; Urinary bladder neoplasms.