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- B2740前上纵隔肿块穿刺
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Extraskeletalmyxoid chondrosarcoma, also referred as chordoid sarcoma in earlier reports, affects adults, in their 3rd to 5th decades, with a male predominance. Most lesions are deep-seated, often intramuscular, and there is a strong predilection for the lower limb.
Extraskeletalmyxoid chondrosarcoma is a multinodular tumor often traversed by fibrous septas. The hyaluronidase-resistant myxoid matrix usually appears almost avascular. Plump eosinophilic tumor cells are most commonly arranged in intersecting cords, although some lesions may be more cellular and simulate a myoepithelial tumor. Cytologic features are variable: tumors may be composed of spindle-shaped cells or round cells resembling PNET. Cytoplasmic hyaline " rhabdoid " inclusions are found in 10 to 20% of cases. Recently a few cases with epithelioid high-grade areas have been reported.
Immunohistochemically, S100 positivity is only seen in 10 to 35% of cases. Most tumors are characterized by a t(9;22) translocation.
Recent studies have demonstrated that the prognosis ofmyxoid chondrosarcoma is poorer than suggested by earlier reports, with a metastatic rate of approximately 45%.
EMC must distinguished from chordoma, which is usually axial and is positive for epithelialmarkers and frommyxoid liposarcoma, which shows a
plexiformvascular pattern. Cellular tumors are virtually indistinguishable frommixed tumors without immunohistochemistry (positivity for keratins and smoothmuscle actin inmixed tumors).
Chondrosarcoma of bone may appear predominantlymyxoid but usually contains more mature cartilage and does not show the lace-like pattern of EMC; the t(9;22) translocation is absent.
骨外黏液性软骨肉瘤的免疫表型应该为：vimentin+、S-100+（40%左右的病例，呈弱阳性或灶阳）、NSE+与PGP9.5+（在部分病例）。
骨外黏液性软骨肉瘤在35岁以上成年男性（多见于50岁-70岁）多发，好发于肢体，少数发生在头颈部或颅内。大小一般在4cm以上，甚至10cm以上。镜下呈多结节状，结节间有纤维分隔。结节内含多少不一的粘液样基质（黏液卡红染色阳性），肿瘤细胞形态为圆形、卵圆形或短梭形，大小较一致，核小而深染，核分裂少见（小于2/10HPF）。胞浆嗜伊红，有时含空泡。
对照本例，形态学有支持之处。但需鉴别于：非骨化的骨化性纤维粘液样肿瘤、粘液性脂肪肉瘤、软骨粘液样纤维瘤、软骨样脂肪瘤等。
- 王军臣
