肾原发性形成脂肪的孤立性纤维性肿瘤临床病理观察

Primary fat-forming solitary fibrous tumor of the kidney: a clinicopathological analysis

目的探讨肾原发性形成脂肪的孤立性纤维性肿瘤(FFSFT)的临床病理特征、诊断与鉴别诊断。方法对1例肾原发性FFSFT组织学形态、免疫组化和MDM2免疫荧光原位杂交(FISH)结果进行分析,并复习相关文献。结果患者男性,59岁。腹部增强CT及彩超示右侧肾内巨大占位性病变。行根治性右肾切除术。巨检见肿瘤界限清楚,切面灰白、灰黄色,质韧,大小12.5cm×9cm×6.5cm。镜下肿瘤由成熟的脂肪细胞和血管外周细胞瘤样结构组成。镜下,血管外周细胞瘤样结构区域的肿瘤细胞呈梭形或卵圆形,细胞界限不清,胞质淡红染,细胞核呈梭形,偶见核仁;细胞形态温和,无细胞异型性和坏死,核分裂象罕见。免疫组化:梭形肿瘤细胞STAT6弥漫强(+),CD34局灶弱(+),而CKpan、S-100、SMA、calponin、HMB45和melan-A均(-),Ki-67增殖指数<3%;MDM2基因未见扩增。术后随访2年,未见肿瘤复发。结论肾原发性FFSFT极其罕见,具有低度恶性潜能,需要与血管平滑肌脂肪瘤、梭形细胞脂肪瘤和高分化脂肪肉瘤等鉴别。梭形肿瘤细胞STAT6阳性对于FFSFT具有重要诊断价值,完整切除是其首选治疗方式。

Objective To investigate the clinicopathological features, pathological diagnosis and differential diagnosis of primary fat-forming solitary fibrous tumor（FFSFT） of the kidney. Methods A case of primary FFSFT of the kidney was reported with histology and immunohistochemical analysis, MDM2 gene translocation was detected by fluorescence in situ hybridization（FISH）, and the available literature of this tumor was reviewed as well. Results A male patient of 59-year-old showed a large mass by CT and ultrasound in the right kidney. Radical right nephrectomy was used for treatment. On macroscopic examination, the well-defined tumor was gray-yellowish on cut surface with rubbery consistence and was sized 12.5×9×6.5 cm. Microscopically, the tumor was composed of mature adipocytes and hemangiopericytoma-like structure. The oval and spindle tumor cells in hemangiopericytoma-like areas were ill-defined, and had weakly eosinophilic cytoplasm and contained spindled nuclei with occasional small nucleoli. The tumor cells were bland without cellular atypia or necrosis and mitoses were rare. Immunohistochemical staining showed that the spindle tumor cells were diffusely and strongly positive for STAT6, focally and weakly positive for CD34, but negative for CKpan, S-100, SMA, calponin, HMB45, and melan-A. Ki-67 index was less than 3%. MDM2 gene translocation was not detected. During the follow-up of 2 years, no tumor recurrence was noted. Conclusions Primary FFSFT of the kidney is an exceedingly rare tumor with low malignant potential. It should be differentiated from angiomyolipoma, spindle cell lipoma, well differentiated liposarcoma and others. Positive expression of STAT6 in the spindle tumor cells is a key feature for FFSFT. The total excision is the prior treatment for FFSFT.