Chondroid lipoma
Chondroid lipomas are rare benign soft tissue tumors that, as you might guess, contain a varied ratio of both fat and cartilage. These lesions can be diagnostically confusing as they may mimic or be confused with other fat containing neoplasms, most importantly those of much greater clinical significance such as myxoid liposarcoma and extraskeletal myxoid chondrosarcoma .
Epidemiology
Age at presentation may range from 14-70 years, with a 4:1 female predominance.
Pathology
Histologic features that suggest chondroid lipoma include a fibrous capsule with nests and cords of uni and multivacuolated round cells within an extracellular myxohyaline matrix that has a cartilaginous appearance. These lesions may have rich vascularization .
To arrive at a specific diagnosis of chondroid lipoma, immunohistochemical analysis may assist in distinguishing these lesions and myxoid liposarcoma or other more aggressive tumors .
Location
An appendicular distribution predominates, with lesions most frequently encountered in the proximal extremities and limb girdles; however, cases have been reported in the trunk, head and neck as well.
Radiographic features
These lesions may vary from predominately fat to predominately chondroid tissue , with imaging features that match the relative distribution of constituent tissues. They also range from sub-centimeter to rather enormous. It is worth keeping in mind that imaging characteristics have not been extremely well-documented due to the rarity of this lesion and recent first description, in 1993.
Plain radiograph and CT
Often seen as a mass like lesion of low density tissue (typically of fat attenuation) with or without internal calcification of the cartilaginous regions; however, fat may not be a prominent feature and may not be readily identifiable .
MRI
Described features include a lobulated, encapsulated mass with areas that show typical fatty signal to a variable degree, with high signal on T1 and T2WI, suppressing with fat saturation. Cartilaginous portions of the lesion will show inhomogeneously increased signal on fluid sensitive fat-suppressed images. Areas of calcification within the mass will appear hypointense on all pulse sequences .
Contrast enhancement
Lesions may show heterogeneous and/or peripheral enhancement.
PET
Lesions may be prominently F-FDG avid .
Differential diagnosis
Imaging differential considerations include:
