Key words myxoid chondrosarcoma of bone; differential diagnosis; immunohistochemistry

0 Introduction

    External skeletal myxoid chondrosarcoma (extraskeletal myxoidchondrosarcoma, EMC) is a rare malignant soft tissue tumors of the reported cases occurred in the right ankle medial EMC, to investigate the clinical and pathological features and differential diagnosis.

    1 Clinical data

    Patients, male, 29 years old, right ankle medial subcutaneous painless lump four years. September 20, 2007 in our hospital line local mass resection, intraoperative see tumor boundaries was clear, solid, quality and tough, broad-based. General observation: the right ankle mass 1.5 cm x 1.1 cm x 0.4 cm, the surface is smooth, gray, complete capsule. See section mass round, soft, clear boundaries, multi-nodular pale jelly. Under a microscope, the tumor was TLC envelope surrounding by thick fiber interval is divided into the tumor nests or nodular, as shown in Figure 1. Lobular see the cells were round or short spindle arranged in cords, cluster or mesh, medium cell mass of the tumor cells, eosinophils, a small number of cytoplasmic vacuolization nucleus round, as shown in Figure 2, staining exquisite, prominent nucleoli, small cell atypia, mitotic approximately 0 to 1/10 the HPF. Tumor cells vimentin is strongly positive, S100, as shown in Figure 3, Syn and Nse are focally positive, Ki67 positive (<5%), CD34, CD31, FV Ⅲ factor, Desmin, CK and EMA were negative, AB staining positive . The pathological diagnosis: right ankle myxoid chondrosarcoma.

    2 Discussion

    EMC is a rare tumor, accounting for less than 3% of soft tissue sarcomas [1], mainly seen in adults, the average age of onset is 50 to 60 years old, the male to female ratio of 2:1. Reported disease 83% occur in the lower extremities [2], in this case, the right ankle subcutaneous lumps, and reported values. At the same time there are a few cases reported in the other parts of the external auditory canal, maxillary sinus and the nasopharynx [3  5]. Common type EMC multi-nodular structure, fiber the interval tumor separated into clear boundaries myxoid or cartilage myxoid stromal area, interstitial rich in sulfuric acid glycoprotein. Immunohistochemistry, vimentin EMC sustained expression markers, S100 protein was focally positive, and in some cases with neuroendocrine markers such as NSE and Syn positive reaction. EMC patients with longer survival, but long-term follow-up found that a high potential for local recurrence and metastasis, disease-related mortality is high. About 50% of cases of local recurrence and metastasis, especially metastasis to the lungs. Tumors, especially greater than 10 cm, is an important prognostic factors.

    EMC is a differentiation pending soft tissue tumors, and to be a variety of soft tissue tumors to identify: (1) epithelial-like hemangioendothelioma: composed of arranged short of the rope and the nested structure of epithelioid endothelial cells of CD31, of CD34 and FV Ⅲ factor etc. can be identified and EMC. (2) mixed tumor / myoepithelioma / Vice chordoma: the Vice chordoma, mixed tumor and myoepithelioma is very similar, they are classified as a class. Mixed tumor is a localized, containing different proportions of epithelial and (or) myoepithelial component, stromal hyalinization or cartilage myxoid. Despite the diversity of this class of tumor morphology, but 95% of cases expressed cytokeratin, vimentin and S100 protein. The patients CK negative expression can rule out the possibility of mixed tumor / myoepithelioma / Vice chordoma. (3) chordoma: the latter occurs mainly in butterfly pillow and sacrococcygeal cell morphology mostly vacuolization, CK, EMA and CEA expression can be used for differential diagnosis between the two.