A 50-year-old woman presents with a painless soft tissue mass in her right thigh. Upon surgical excision, the surgeon notices that the tumor is adherent to the surrounding tissues. Histologic analysis reveals a neoplasm composed of pleomorphic clear cells, with vacuolated cytoplasm. The nucleus of many cells is indented by the cytoplasmic vacuoles, which are stained by histochemical methods for lipids. Which of the following is the most likely diagnosis?
Liposarcoma is one of the most common soft tissue tumors, affecting middle-aged and elderly persons. The thigh and retroperitoneum are the most frequent sites. The tumor is composed of pleomorphic lipocytes that resemble embryonal lipoblasts. The cytoplasm of neoplastic cells is filled with lipid vacuoles (positive for fat stains), which characteristically indent the nuclear membrane. The prognosis of liposarcomas, as of all soft tissue tumors, is dependent predominantly on location and age (deep tumors in elderly patients behave more aggressively than ones in superficial locations in younger patients). Chondrosarcoma arises from cailage, most often in the pelvic region. The tumor consists of anaplastic chondrocytes that produce a basophilic intercellular substance known as chondroid. Lipoma is microscopically identical to mature fat tissue. It is composed of adipocytes with a single large cytoplasmic droplet that displaces the nucleus to the periphery. Metastatic adenocarcinoma would be composed of glandular structures. Special stains for mucin highlight mucin production, but stains for fat would be negative.
Chondrosarcoma
Lipoma
Liposarcoma
Metastatic adenocarcinoma