The patient presented with a swelling in his distal right thigh, just above the popliteal fossa. He had first noticed this swelling about two months before and he reported that it had been slowly growing during this period. There was no pain but he had some difficulty in flexing his leg.
The patient presented with a swelling in his distal right thigh, just above the popliteal fossa. He had first noticed this swelling about two months before and he reported that it had been slowly growing over this period. There was no pain but he had some difficulty in flexing his leg.
An MRI of the thigh was performed in all three planes with spin echo Proton Density and T2-weighted sequences as well as spin echo T1-weighted and spin echo T1-weighted fat-suppressed sequences, pre- and post-contrast administration. This showed a large well-defined mass lesion deeply seated in the posterior aspect of the distal thigh between the biceps femoris muscle laterally and the semimembranosus and semitendinosus muscles medially. The tumour displayed marked heterogeneity with hypointense internal septae and areas with signal intensity consistent with fat (Figs 1,2). Post-contrast enhancement was markedly inhomogeneous (Fig. 3). A diagnosis of myxoid liposarcoma was suggested, which was pathologically proven after a wide margin surgical excision of the tumour.
Myxoid liposarcoma is the most frequent subtype of all liposarcomas, accounting for 40-50% of all cases. It is a low-grade tumour with a higher incidence between the ages of 40 and 60 years. Myxoid liposarcomas occur in the intermuscular fascial planes or deep-seated areas. They are rarely found in subcutaneous tissue. They commonly involve the thigh and the popliteal region. The clinical presentation includes a large, slow-growing, painless mass. The mass is relatively soft and nontender on palpation.
Myxoid liposarcomas are gelatinous tumours that on gross examination reveal a lobulated pattern with some areas that appear like those of a lipoma and other areas that look myxomatous. On microscopic examination it is common to find a delicate pattern of capillaries running through the myxoid areas [1-3].
A spectrum of MR imaging abnormalities occur in myxoid liposarcoma, depending on the amount of fat and myxoid material, the degree of cellularity and vascularity, and the presence of necrosis. Most myxoid liposarcomas have lacy or linear, amorphous foci of fat. On MR imaging they typically appear as a well-defined mass, often lobulated, with a heterogeneous high and low signal pattern that is not present in cases of benign lipoma. Areas of fatty elements are typically hyperintense on T1-weighted images.Myxoid liposarcomas rarely present with an abundance of fatty components, as in our case. This appearance is more often a feature of pleiomorphic liposarcomas. There is no evidence of infiltration or invasion into adjacent structures. Some myxoid liposarcomas may not exhibit the signal intensity typical of a fatty tumour and may instead appear as cystic masses on non-enhanced images. In this case they appeared homogeneous, hypointense on T1-weighted images and markedly hyperintense on T2-weighted images. In this setting a myxoid liposarcoma has to be differentiated from other lesions such as a benign myxoma. However, myxoid liposarcomas show intense enhancement of 65–100% of the tumour volume in most cases [2-4].Dynamic contrast-enhanced subtraction MR images have been proven to be useful in differentiating malignant from benign soft tissue masses [5]. With this technique soft tissue masses can be characterized fairly accurately on the basis of early enhancement, pattern of enhancement and progression of enhancement.
Because myxoid liposarcomas are classified as low grade tumours their distinction by MRI from more aggressive tumours has surgical and prognostic implications. Although myxoid liposarcoma mostly has a good prognosis, local recurrences after surgical resection are frequently seen, sometimes compromising limb integrity.The tumour should be surgically removed with wide margins [1].
Myxoid liposarcoma of the distal thigh
The patient is a 44-year-old male with a large soft tissue mass in the distal right thigh (near the popliteal region). Based on the provided MRI images:
Considering the patient’s age, clinical presentation (slow-growing, painless mass), and the imaging characteristics (mixed fatty and myxoid components), the following differential diagnoses should be considered:
Based on the patient’s age, the location of the lesion (distal thigh near the popliteal region), the slow-growing, painless nature of the mass, and MRI findings indicating abundant myxoid components mixed with fat, in conjunction with pathological experience, the most likely diagnosis is: Myxoid Liposarcoma.
For definitive diagnosis, a biopsy or surgical resection followed by pathological examination is still recommended to clarify tumor grade and characteristics.
Postoperative rehabilitation may follow the FITT-VP principle (Frequency, Intensity, Time, Type, Progression, Volume). A general plan is outlined as follows:
If significant pain, swelling, or worsening functional impairment occurs at any point, stop exercising and seek medical attention promptly.
This report provides a reference for medical analysis and does not replace an in-person consultation or the opinion of a professional healthcare provider. Patients should consult with a qualified physician to develop a definitive treatment and rehabilitation plan tailored to their individual situation.
Myxoid liposarcoma of the distal thigh
