OBJECTIVETo study the clinicopathologic features of dendritic fibromyxolipoma for the purpose of differentiating it from other confusable soft tissue neoplasms.

METHODSEight cases of dendritic fibromyxolipoma were obtained and their clinicopathologic features were studied. Immunohistochemistry stains for CD34, bcl-2, vimentin, cytokeratin, EMA, S-100, HHF35 and smooth muscle actin were performed with labeled streptavidin-biotin (SLAB) system on DAKO auto-immunohistochemical stainer.

RESULTSDendritic fibromyxolipoma usually occurrs in middle-aged to elderly men, developing primarily in the subcutis or muscular fascia of the head and neck region, shoulder, back, calf and foot. Grossly, it is well-circumscribed, partly thinly encapsulated lesion with focal mucinous or gelatinous cutting surface. Histologically, all these tumors showed similar histological features., and were characterized by an admixture of mature adipose tissue, spindle and stellate cells, and abundant myxoid stroma with prominent collagenization. The proportion of above elements varied in different tumors or in different areas within the same tumor. One of the pathologic characteristics was the proliferation of spindle cells and stellate cells showing thin cytoplasmic dendritic prolongations. No cytological atypia or mitotic activity could be identified. Furthermore, the lesions were well-vascularized and the vascular elements consisted of small to median-sized and capillary-sized plexiform vessels. Spindle cells were strongly positive for CD34, bcl-2 and vimentin but negative for S-100 protein and epithelial and muscle markers.

CONCLUSIONSDendritic fibromyxolipoma is characterized by clinicopathologic and immunohistochemical features. Based on those features of this tumor, this entity appears to represent a transitional form between spindle cell lipoma and solitary fibrous tumor, and should be distinguished from myxiod liposarcoma and myxoid malignant fibrous histiocytoma. Due to the benign nature of this lesion, simple local excision is curative.