Teaching Case

A 59-year-old female patient with a slowly growing mass of the left hand.

A 59-year-old female patient was referred due to slowly growing mass of the left hand over a period of approximately 2 years. The physical examination showed a soft tissue mass of the thenar region on the left hand, which was unrelated to and easily movable on the neighboring structures. An MRI study was performed on a 1.5 T MR scanner, with SE T1, FSE T2, fat-suppressed FSE T2 sequences on three orthogonal planes.

Soft tissue lipomas are the most common mesenchymal tumors, which are homogeneous and clearly marginated, with or without internal septations. They usually appear in the fifth to sixth decades of life, and the males are more affected than the females. They reach a stable size after an initial period of discernible growth. These soft tissue tumors are found most commonly in the subcutaneous regions of the posterior trunk, neck, shoulder, proximal extremities. They lodge in deeper locations such as within the thigh, retroperitoneum, anterior mediastinum, gastointestinal wall, deep soft tissues of the hands and feet less frequently . Histopathologically they are composed of mature fat cells that are uniform in size and shape, they may have fibrous connective tissue as septations. Lipomas of the hand are not common neoplasms. Although ultrasonography, computed tomography can be used for the diagnosis and evaluation of the lipomas, MRI is the imaging method of choice for evaluating the presence and extent of the lipomas, providing excellent anatomic detail and soft tissue contrast. Lipomas are well defined masses, with signal intensity characteristics similar to subcutaneous fat, hyperintense on T1 weighted spin-echo, and moderately intense on T2-weighted fast spin-echo images on MRI. The signal intensity of lipomas is nulled on fat-suppressed T2-weighted fast spin-echo images or STIR images. Low signal intensity septations may be seen within the lesions on all sequences. Lipomas do not show contrast enhancement after IV gadolinium injection. The differential diagnosis of lipomas from certain conditions like ganglion, hemangioma, arteriovenous malformation, giant cell tumor of the tendon sheath in the hand is not difficult with the characteristic MRI findings.