Pleomorphic liposarcoma of the thigh

A 60-year-old man presented with right thigh pain for the past 3 months. He also noted a mass progressively growing at his right thigh around this time. He did not seek medical advice until now.

He denied any significant past medical illnesses or surgical history. He had no history of radiation exposure, no recent trauma, and no personal or family history of malignancies. He denied any fever, weight loss, sensory loss or motor weakness. Physical examination revealed a 24 cm right thigh mass that was tender to palpation. There was no surrounding erythema or warmth.

Plain film of the right thigh did not reveal any recent fracture, dislocation or bone destruction nor was there any radiopaque foreign body identified. No abnormal calcification was noted. There was abundant soft tissue swelling noted in the area of the right proximal to mid-thigh.

MRI of the thigh revealed a large mass arising from the medial compartment of the thigh measuring approximately 23 cm in craniocaudal dimension × 14 cm in anteroposterior dimension × 13.5 cm in transverse dimension. The superior extent of the tumor was from the upper thigh to the level of the subtrochanteric region; the inferior extent of the tumor is approximately 16 cm from the femorotibial joint space.

The tumor displaces the sartorius and gracilis muscles medially and hamstring muscles posteriorly. The tumor abuts the posterior medial aspect of the femur. The superficial femoral artery and vein are displaced anteriorly. The adductor muscles are either invaded or extremely compressed. The sciatic nerve could not be delineated among the markedly compressed surrounding tissues. There were edematous changes around the tumor, especially at its inferior and superior aspects. The edematous changes also extended into the anterior compartment.

Figure 1. Plain radiograph of the right lower extremity demonstrates increased soft tissue medial to the right femur (red arrows). There is no evidence of periosteal reaction or bone erosion.

The bone marrow signal intensities were within normal limits. With gadolinium injection, this tumor showed reticulated enhancement, especially at its periphery. There was no evidence of macrofat within the tumor.

CT of the chest, abdomen and pelvis did not show any evidence of metastases. He also had deep venous thrombosis of right popliteal vein on vascular ultrasound. He was placed on oral anticoagulation and underwent inferior vena cava filter placement.

The thigh mass was radically excised. Intraoperatively, the large soft tissue mass was found occupying the entire adductor compartment. It was adherent to the femoral vessels, and its posterior margin was essentially the sciatic nerve. Pathology was consistent with pleomorphic liposarcoma: tumor size 16 cm × 18 cm × 12.6 cm, FNCLCC score 3/3 differentiation, high grade 2/3, mitotic rate 6/10 per high power field with less than 50% tumor necrosis, and positive inferior and medial margins but without lymphovascular invasion (pT2bNxMx).

Liposarcomas are malignant neoplasms with fatty differentiation. They are subdivided histologically into well-differentiated/dedifferentiated liposarcoma, myxoid/round cell liposarcoma, and pleomorphic liposarcoma.

Figure 2. (Clockwise from the upper left: non-fat saturated axial T1 without contrast, non-fat saturated axial T2, fat saturated axial T1 with contrast, fat saturated axial T1 without contrast). MRI images demonstrate a large mass with heterogeneous signal intensity along the medial compartment of the thigh abutting the medial femur. The skeletal marrow signal appears normal. The femoral artery is displaced anteriorly and the muscles are splayed apart. There is no appreciable fat signal within this mass, although this does not exclude the possibility of a liposarcoma.

Pleomorphic liposarcoma is the rarest subtype of liposarcoma, representing about 5% of all liposarcomas. It is a clinically, histologically and cytogenetically distinct form of liposarcoma. It presents in adults, usually between the sixth and seventh decades. Progressive development of a painless soft tissue mass is the most common presentation, as was seen in our patient.

It has a strong predilection for deep soft tissues of the proximal extremities. It can also be seen in the thoracic and abdominal wall, retro/peritoneum, pelvis, spermatic cord and rarely in the mediastinum, parietal pleura and head and neck. In a study by Downes and colleagues and Mentzel and colleagues, the majority of PLS were deep seated and/or extracompartmental. They can be superficial in about 20% of cases, located within the subcutaneous fatty tissue and involving the dermis in a limited number of cases.

It is best differentiated from other high-grade sarcomas by the presence of pleomorphic lipoblasts on hematoxylin and eosin staining. It has a poor differentiation; the nucleus is either pushed aside by a single large vacuole, resulting in signet ring configuration, or is central similar to sebaceous cells or spongiocytes of the adrenal cortex. Immunohistochemistry has a limited role in diagnosis.

Figure 3. (Clockwise from the upper left: fat saturated coronal T2, fat saturated coronal T1 with contrast, fat saturated sagittal T1 with contrast, non-fat saturated sagittal T2). Additional MRI images in the coronal and sagittal planes demonstrate the large size and heterogeneity of the lesion. Note the circumferential enhancement with disorganized reticular internal enhancement highly suggestive of a malignant process. Courtesy of M Ghesani, MD

PLS is a relatively aggressive tumor with 5-year survival ranging from 29% to 57%. The lung is the most common site of metastasis. Differential diagnosis includes leiomyosarcoma, rhabdomyosarcoma, malignant peripheral nerve sheath tumor, dedifferentiated liposarcoma, myxofibrosarcoma, carcinoma and melanoma.

A size of less than 10 cm, mitosis fewer than 10/10 high power fields and predilection to the extremities are associated with a favorable prognosis while the presence of tumor necrosis and epithelioid areas may be associated with worse prognosis.

Management is similar to other soft tissue sarcomas; surgery is the mainstay of treatment with or without adjuvant radiation therapy or chemotherapy.

Irene Dy, MD, is a fellow in hematology and oncology at St. Luke’s-Roosevelt Hospital Center.

Neilish Gupta, MD, is a radiology resident at St. Luke’s-Roosevelt Medical Center.

Munir Ghesani, MD, is associate clinical professor of radiology at Columbia University College of Physicians and Surgeons and Attending Radiologist at St. Luke’s-Roosevelt Medical Center.

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