Fibrolipoma

July 26, 2013



Clinical history: An 18-year-old male patient with no apparent trauma presents with the appearance of swelling on the side of the thigh region.

The ultrasound exam showed solid formation, slightly uneven but regular margins of about 5 cm below the subcutaneous adipose tissue, with small liquid water on the medial margin of the lesion. On surgical indication, runs an MRI without contrast medium.

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Figure 1: MRI FSE T2 Ax

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Figure 2: MRI SE T1 Ax

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Figure 3: MRI GE T2 Ax

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Figure 4: MRI FSE T2 Fat Sat Ax

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Figure 5 MRI SE T1 Cor
The survey is integrated with MRI CT examination

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Figure 6: CT Ax soft window

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Figure 7: CT Cor soft window

MRI examination documents the presence of a liquid collection saccata about 5 x 1, 5 x 9 cm inside which is evident with training of approximately 5 cm with morphology and signal refer to adipose tissue. The formation is removed surgically.

Diagnosis: Fibrolipoma with widespread phenomena of liponecrosi and with distinct angectasici and fibroplastici phenomena.

Discussion: Soft tissue tumors are derived predominantly from primitive mesenchyme. Probably the most common mesenchymal tumor is lipoma, a benign tumor composed of mature adipose tissue. Patients with a soft tissue lipoma typically present in middle age (fifth and sixth decades).

A soft tissue lipoma is categorized by anatomic location as either superficial (cutaneous) or deep. The superficial lipoma occurs more commonly and is more sharply circumscribed and smaller in size than its deep-seated counterpart. A superficial (subcutaneous) lipoma may be inapparent, blending in with the adjacent subcutaneous fat on MRI. Unless a marker is placed over the mass before imaging, it may appear only as a thickening of the subcutaneous fat.

The pathogenesis of lipoma is unknown, although it is thought to represent a true mesenchymal neoplasm. It is usually a solitary lesion, although a small percentage of patients (5 percent to 7 percent) demonstrate multiple tumors, which can vary in number from a few to several hundred.

lnterestingly, the fat within the lipoma is unavailable for systemic metabolism and, paradoxically, may actually increase in size during starvation.

The lipoma is well characterized on MRI, with the lesion having an appearance identical to that of subcutaneous fat on all pulse sequences, without discernible enhancement after the administration of intravenous gadolinium.

Lipomas occasionally contain other mesenchymal elements. The most common of these is fibrous connective tissue, which may be in the configuration of septa and therefore appear as linear densities on CT or linear areas of decreased signal on MRI, regardless of pulse sequence. When significant fibrous tissue is present, these lesions may be termed fibrolipoma.

A few cases of malignant transformation of lipoma have been reported, but these may represent cases where the subtle histologic features of malignancy were initially overlooked.

Matteo Battista, TSRM
Graduate Radiology Technologist
San Marco in Lamis, Italy