Pathology of Chondroid Lipoma
Chondroid lipoma is a rare, benign variant of lipomatous tumour.
Age and sex: Chondroid lipoma occurs predominantly in the third decade of life, mostly in females (female-male ratio, 4:1).
Site: These are usually located in the subcutaneous tissue, superficial muscular fascia, or skeletal muscles, especially in proximal limbs and limb girdles.
Gross: Encapsulated and lobulated mass usually about 4 cm in maximal dimension. Image
Microscopic Image of Chondroid Lipoma
The tumour is composed of a varying admixture of eosinophilic multivacuolated cells arranged in strands, nests and sheets together with mature adipocytes.
These are present in a myxoid and chondroid-like stroma.
Multivacuolated cells contain contain fat and glycogen (demonstrated by periodic acid Schiff and Oil-red-O stains) and may resemble chondroblasts or hibernoma cells.
There may be areas of fibrosis and hemosiderin deposition.
There is little pleomorphism and mitotic activity is low.
Usually Vimentin and S 100 protein positive (strongly in adipocytes, weakly in lipoblasts.)
CD68 and cytokeratins may be positive in some cases.
EMA is negative.
MIB1 proliferation index less than 1%.
Cytogenetics: Revealed a balanced translocation t (11,16) (q13; p12 -13).
2.Extraskeletal myxoid chondrosarcoma - Tumour is more lobulated with fibrous septa and presence of a thin peripheral capsule. There is absence of adipocytes and lipoblasts. Tumoral chondroblasts are more round and have few or no intracytoplasmic vacuoles.
4. Mixed tumor -There are foci of epithelial differentiation, lipoblasts are absent.
Note: If the pathologist is unaware of the entity he may consider a sarcoma either of adipose tissue - a round cell liposarcoma - or of cartilage- an extraskeletal myxoid chondrosarcoma.
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