de Saint Aubain Somerhausen N, Rubin B P, Fletcher C D
Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Mod Pathol. 1999 May;12(5):463-71.
Focal myxoid change is a well-recognized feature of solitary fibrous tumor (SFT), but to date, predominantly myxoid examples of SFT have not been reported. We describe seven cases of SFT in which stromal myxoid change affected 50% or more of the tumor examined, thus obscuring typical diagnostic features. Patients ranged in age from 35 to 68 years old (median, 45 yr), with an equal sex distribution. Tumor locations included pleura, orbit, and periparotid subcutaneous tissue, as well as four cases in deep soft tissue (two in the abdominal wall and one each in the chest wall and thigh). Myxoid areas were identified grossly in four cases. Histologically, the lesions were composed of bland spindle cells disposed haphazardly or with a lacy or reticulated appearance in a myxoid, richly vascularized stroma These myxoid areas were punctuated by small cellular aggregates in four cases, and areas showing diagnostic features of SFT were present in five of seven primary excision specimens. Atypical features suggestive of malignancy were not present in any of the cases. Immunohistochemically, all of the seven cases stained positively for CD34 and CD99 (013), and all were negative for smooth muscle actin, desmin, S-100 protein, epithelial membrane antigen, and pan-keratin. There were no recurrences or metastases reported in four patients with limited follow-up (median duration, 19 mo). Recognition of this uncommon morphologic subset of SFT is important because of possible confusion, particularly in small biopsy specimens, with a variety of myxoid spindle cell neoplasms with different biologic potential. These include low-grade fibromyxoid sarcoma, myxoid synovial sarcoma, malignant peripheral nerve sheath tumor, low-grade myxofibrosarcoma, myxoid liposarcoma, myxoid spindle cell lipoma, myxoid neurofibroma, and so-called "hemangiopericytoma."
局灶性黏液样变是孤立性纤维性肿瘤（SFT）的一个公认特征，但迄今为止，主要为黏液样的SFT病例尚未见报道。我们描述了7例SFT，其中间质黏液样变累及所检查肿瘤的50%或更多，从而掩盖了典型的诊断特征。患者年龄在35至68岁之间（中位数为45岁），男女分布均等。肿瘤部位包括胸膜、眼眶、腮腺周围皮下组织，以及4例深部软组织肿瘤（2例位于腹壁，1例位于胸壁，1例位于大腿）。4例大体可见黏液样区域。组织学上，病变由形态温和的梭形细胞组成，这些细胞随机排列或呈花边状或网状，位于黏液样、血管丰富的间质中。4例黏液样区域有小细胞聚集，7例原发切除标本中有5例可见具有SFT诊断特征的区域。所有病例均未出现提示恶性的非典型特征。免疫组化方面，7例均CD34和CD99（013）染色阳性，平滑肌肌动蛋白、结蛋白、S-100蛋白、上皮膜抗原和泛角蛋白均为阴性。4例随访有限（中位随访时间19个月）的患者均未报告复发或转移。认识到SFT这一不常见的形态学亚型很重要，因为它可能会与多种具有不同生物学潜能的黏液样梭形细胞肿瘤混淆，尤其是在小活检标本中。这些肿瘤包括低级别纤维黏液样肉瘤、黏液样滑膜肉瘤、恶性外周神经鞘瘤、低级别黏液纤维肉瘤、黏液样脂肪肉瘤、黏液样梭形细胞脂肪瘤、黏液样神经纤维瘤以及所谓的“血管外皮细胞瘤”。
