MRI诊断左小腿促结缔组织增生性小圆细胞肿瘤一例

韩晓兵，张乾营，阿浣

HAN Xiao-bing, ZHANG Qian-ying, A Huan

MRI诊断左小腿促结缔组织增生性小圆细胞肿瘤一例

韩晓兵，张乾营，阿浣

HAN Xiao-bing, ZHANG Qian-ying, A Huan

患者女，27岁，发现左小腿渐进性增大肿物1个月余入院。于入院前1个月患者无明显诱因出现左小腿外侧肿痛，站立时间较长、行走久时症状明显，无低热、盗汗、夜重昼轻等不适，与天气变化无关，仍可行走及锻炼。MRI检查：左小腿上段偏外侧软组织可见不规则分叶状软组织肿块，T1WI呈稍低信号(图1A)，T2WI呈混杂低信号，内部见斑点状稍高信号(图1B)，T2脂肪抑制相肿块呈混杂信号(图1C)，范围约4.3 cm×6.9 cm，边界不清，其内可见流空血管影，病灶邻近周围软组织可见斑片状水肿，T1WI增强扫描示肿块呈明显不均匀强化，并可见不强化坏死区域(图1D)；邻近左腓骨上段骨皮质连续，骨髓腔内在T2脂肪抑制相上可见斑片状高信号，边界不清。术中所见：左小腿外侧上段肿物，肿物无明显界限，活动度差，肿物呈分叶、灰白色、鱼肉状。术后病理：瘤组织排列成不规则细胞巢，细胞排列紧密，核呈圆形或卵圆形，深染，核仁不清，核分裂象易见，胞质稀少，瘤细胞巢间及其周围为大量增生的致密纤维结缔组织，部分伴有玻璃样变性。免疫组化标记结果：CD99(+++)，SMA (－)，Desmin (－)，CgA (－)，Syn(－)，CD56 (－)，EMA (－)，LCA (背景淋巴细胞+)。病理证实为促结缔组织增生性小圆细胞肿瘤(desmoplastic small round cell tumor，DSRCT)。

讨论 1989年Gerald和Rosail首次报道本病[1]，并1991年正式命名[2]。DSRCT是由组织起源未定的小圆肿瘤细胞构成，伴有明显间质硬化和表型分化的高度恶性肿瘤，好发年龄为18～25岁，男女比例为3.8～5:1，但也有报道老人和年轻女性可患此病[3-4]，基本发生在腹腔内，偶见胸腔、睾丸区及头颈部[5-8]，笔者复习查阅既往文献，尚无发生于小腿的病例报道，流行病学特征有待大宗病例统计。张沈荣等[9]和Pickhardt等[10]认为DSRCT最典型的征象是没有明确的起源器官，多数病灶位于大网膜、肠系膜根部或者膀胱周围，表现为孤立性、多发性的软组织肿块。影像学检查是DSRCT术前的主要检查手段，但不能明确性质，确诊得依靠病理。CT或MRI可发现单个或多个分叶状软组织肿块，内部可见坏死，偶见钙化，增强呈不均匀强化。本病在病理学及影像学上发生于腹腔外的与腹腔内的无明显区别，但发生于四肢的病例需与以下病变鉴别：(1)未分化高级别多形性肉瘤：多见于老年(60～70岁)男性，好发于下肢深部软组织，边界不清，易侵犯邻近骨质结构和发生远处转移，与发生于老年人的DSRCT并无可鉴别的特殊征象。(2)黏液纤维肉瘤：多见老年男性，且发生于四肢的皮下软组织，影像特征不明显，一般T1WI及T2WI为混杂信号。(3)平滑肌肉瘤：中老年人多见，好发于腹腔、腹膜后等，四肢亦可发生，相对较少见，四肢中下肢深部软组织多见，易出血、坏死，MRI表现多呈等T1WI信号，稍长T2WI信号，与发生于四肢的DSRCT亦难以鉴别。(4)恶性外周神经鞘瘤：好发于成年人及老人，T1WI、T2WI多呈等信号，瘤内易囊变、坏死及钙化，瘤周可见水肿带，增强扫描肿瘤实性成分呈中等强化，本病例多见于青年，增强呈明显不均匀强化。

图1 病灶位于左小腿上段偏外侧软组织，邻近左腓骨上段骨质受累。A：T1WI示病灶呈稍低信号，其内可见留空血管影，左腓骨上段呈稍低信号；B：T2WI示病灶呈混杂低信号，周围可见斑片状稍高水肿信号；C：T2WI脂肪抑制序列示病灶呈混杂信号，中央呈稍低信号，周围水肿呈高信号；D：T1WI增强扫描示病灶呈明显不均匀强化，周围水肿未见强化 图2 瘤组织排列成不规则细胞巢，细胞排列紧密，核呈圆形或卵圆形，深染，核仁不清，核分裂象易见，胞质稀少，瘤细胞巢间及其周围为大量增生的致密纤维结缔组织，部分伴有玻璃样变性(HE ×200)Fig. 1 Focus was located in the lateral soft tissue on the upside left leg. The adjacent left fibula is involved. A: T1WI showed that the focus presents the lower signal with empty blood vessel. The left fibula presents the lower signal. B: T2WI presents that the focus were mixed with lower signals. There was the higher edema signal in a flaky shape. C: T2WI fat suppressed sequence showed that the focus presents the mixed signal. The central part showed the lower signal and surrounding edema presents the higher signal. D: T1WI enhanced scanning showed that the focus were obviously inhomogeneous and the surrounding edema was not enhanced. Fig. 2 The tumor tissue was arranged into the irregular nests of cells closely. The nucleus was round or oval. With deep stain and unclear nucleolus, nucleolus mitotic figure was obvious. Rare cytoplasm. A large number of dense fibrous connective tissue was found in the nests of tumor cells.Some were accompanied with hyaline degeneration (HE ×200).

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MRI diagnosis of desmoplastic small round cell tumor on left leg: A case report

Desmoplastic small round cell tumor; Magnetic resonance imaging

结缔组织增生性小圆细胞肿瘤；磁共振成像

中国人民解放军第一八○医院医学影像科，泉州 362000

Department of Medical Imaging, the 180th Hospital of People's Liberation Army, Quanzhou 362000, China

2017-04-14 接受日期：2017-06-07

R445.2；R738.6

B

Received 14 Apr 2017, Accepted 7 June 2017

10.12015/issn.1674-8034.2017.07.011