Clinical History
A 54-year-old man with no significant previous clinical history was referred for evaluation of a painless slow growing right latero-cervical mass.
Imaging Findings
Neck ultrasound revealed a bulky heterogeneous cervico-mediastinal lesion composed by an upper hypoechoic solid component and a lower hyperechoic mass. Chest radiography demonstrated enlargement of the anterosuperior mediastinum with lobulated borders. Contrast-enhanced MRI showed the presence of cervicomediastinal mass composed by an upper component (7 cm) with soft tissue signal intensity and contrast enhancement and lower adipose component (15 cm) with thickened and enhancing septa. The preoperative CT examination that confirmed the presence of a homogeneous low density mediastinal mass with compression of the innominate and the azygos veins with internal mammary ectatic venous collateral pathways and displacement of the epiaortic arterial vessels, thoracic aorta, trachea and oesophagus.
An ultrasound-guided biopsy was performed and a well-differentiated sarcoma was diagnosed.
At surgery, a large encapsulated mass was removed and the pathological diagnosis was a well-differentiated liposarcoma with inflammatory, sclerosing and lipoma-like components. The patient is now undergoing an adjuvant radiation treatment.
Discussion
A. Background
Primary mediastinal liposarcomas are extremely rare thoracic neoplasms and are classified in four histological types: well-differentiated, myxoid, pleomorphic and dedifferentiated. Well-differentiated liposarcoma is the most common subtype and has the best prognosis [1, 2].
B. Clinical Perspective
Mediastinal liposarcoma usually occurs in middle-aged patients and presents with unspecific symptoms such as dyspnoea, cough, chest discomfort or superior vena cava obstruction. At least 15% of patients are asymptomatic.
While liposarcoma is the most common retroperitoneal fatty lesion, it is extremely rare in the mediastinum. The more frequent mediastinal fat-containing lesions are germ cell neoplasms, thymolipomas, lipomas, lipomatosis and lipoblastoma [1, 2]. MRI imaging could be useful in the differential diagnosis of a mediastinal fat-containing lesion, in order to distinguish mediastinal liposarcoma from the other more common and less aggressive fatty lesions of the chest. CT is useful in determining the relationship with the other mediastinal components and could help the clinician in the surgical planning.
C. Imaging Perspective
The usual imaging findings of mediastinal liposarcoma are widening of the mediastinum at chest radiography, sometimes with deviation of the trachea, and a heterogeneous fatty mass with variable enhancing solid component at CT and MRI [1, 2]. Some MR imaging findings are more specifically associated with well-differentiated liposarcoma, such as thickened or nodular septa, associated non-fatty tissue, foci of high T2-signal intensity and contrast enhancement [3]. These imaging features along with the growth rate and the mass effect on the surrounding structure should raise the suspicion of malignancy and help differentiating them from lipomas, the more frequent fatty benign counterpart.
D. Outcome
Well-differentiated liposarcomas usually do not metastasize, however, they have high rate of local recurrence (40%) and potential for late dedifferentiation into higher-grade sarcomas [1, 2]. The recommended treatment is surgical excision sometimes with adjuvant radiotherapy to reduce the risk of local recurrence.
E. Take Home Message, Teaching Points
Even if mediastinal liposarcoma is a rare neoplasia, it should be taken into consideration in the evaluation of a fatty mediastinal mass. While MRI is useful in solving the differential diagnosis, CT is helpful in the surgery planning.
Differential Diagnosis List
Cervico-mediastinal well-differentiated liposarcoma
Lipoma or lipomatosis
Thymoma or thymic carcinoma
Thyroid neoplasia
Teratoma
Thymolipoma
Final Diagnosis
Cervico-mediastinal well-differentiated liposarcoma
