肌样型隆突性皮肤纤维肉瘤中肌样区域的组织发生和性质

Histogenesis and nature of myoid areas in myoid type of dermatofibrosarcoma protuberans

目的 探讨肌样型隆突性皮肤纤维肉瘤 (DFSP)中肌样区域的组织发生和性质。方法 对 95例DFSP中筛选出的15例肌样型DFSP进行光镜和免疫组织化学研究。结果 临床资料显示女性比男性稍多见 (1 5∶1)。 18～ 4 0岁为发病高峰年龄段 (73% )。肿瘤部位常见于躯干和肢体 (11/15 )。镜检 :在 15例肌样型DFSP中 (9例为纤维肉瘤型 ,最为常见 ;4例为经典型 ;2例为色素型 ,后者伴有肌样区域未见文献报道 )均观察到散在分布的肌样结节和肌样束 ,即肌样区域 ,且与瘤内血管壁平滑肌细胞增生有密切的关系 ,并发现血管壁改变具有不同程期的特点。早期 :瘤内小血管和少许较大血管壁平滑肌细胞显著增生 ,细胞无异型性 ,可见核分裂象 ;中期 :增生的平滑肌细胞形成特征性的嗜伊红性肌样结节和肌样束 ,可伴轻度玻璃样变 ,在大多数肌样结节和肌样束中常可见偏位、不规则、变小变窄的血管腔 ;后期 :肌样结节和肌样束可相互融合 ,血管腔萎陷或消失 ,伴有广泛玻璃样变甚至钙化。免疫表型 :肌样结节和肌样束呈SMA、MSA、Vim弥漫强阳性 ,但对Des、smoothmusclemyosin、caldesmon和CD34均呈阴性。需特别指出的是肌样结节和肌样束中偏位的血管腔衬覆的内皮细胞呈CD34阳性 ,证实了肌样区域与血管壁的密切关系。

Purpose To explore the histogenesis and nature of myoid areas in myoid type of dermatofibrosarcoma protuberans(DFSP). Methods Fifteen myoid type of DFSP were selected from 95 DFSPs at our institution, and were studied by light microscopy and immunohistochemistry. Results Clinical data showed females were slight more affected than males (1.5∶1). The peak incidence of ages ranged from 18～40 years (73%). The trunk and extremities (11/15)were most frequently involved. Microscopically, the characteristic features of haphazard scattered myoid nodules and bundles (myoid areas) were noted in all 15 tumors, including the most common 9 fibrosarcomatous type, 4 classic type and 2 pigmented type, in which myoid areas was not reported. We observed that the myoid areas had closed relationship with hyperplasia of smooth muscle cells in the wall of the intraneoplastic blood vessels, and different staged changes were discovered as well. At the initial phase, smooth muscle cells in the wall of the intraneoplastic small and a little large blood vessels exhibited conspicuously hyperplasia, cells were lack of atypia, but mitotic figures might be seen occasionally. At intermediate phase, hyperplastic smooth muscle cells formed distinctive acidophilic myoid nodules and bundles, and associated with mild hyalinization, in which the vascular lumina became eccentric, irregular, reduced in size and narrowed. At late phase, myoid nodules and bundles could be confluented each other, inside of it the vascular lumina were ultimately collapsed and disappeared, and associated with extensive hyalinization, and even calcification. Immunohistochemically, cells of myoid areas in all tumors were strongly diffuse positivity for SMA, MSA and vimentin, while negative for desmin, smooth muscle myosin, caldesmon and CD34. It should be particularly indicated that CD34 positive for endothelium of eccentric vascular lumina in myoid nodules and bundles confirmed its blood vessel wall origin. Conclusions Myoid type of DFSP is a rare histologic subtype. It suggests that the histogenesis of myoid areas is originated from hyperplasia of smooth muscle cells in the wall of the intraneoplastic blood vessels. The nature of the myoid areas belongs to non-neoplastic component. Myoid area is neither originated from myofibroblastic differentiation of tumor cells nor from reactive hyperplasia of myofibroblast.But in certain circumstance the hyperplastic vascular smooth muscle cell may transform to myofibroblast.