Pathology of Chondroid Lipoma

Dr Sampurna Roy MD                       2022  

Chondroid lipoma is a rare, benign variant of lipomatous tumour. It was first reported by Meis and Enzinger in 1993.

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.

Microscopic features:    

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.

Immunohistochemistry: 

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).

Differential Diagnosis:  

1. Myxoid liposarcoma - Characterized by a plexiform vascular network and higher cellularity with true lipoblasts.

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.

3. Extraskeletal chondroma - Located in the distal extremities,  multinucleated giant cells and true cartilaginous areas are present. There are no intracytoplasmic fat 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.

Intramuscular chondroid lipoma: magnetic resonance imaging diagnosis by 'fat ring sign'.

Presence of C11orf95-MKL2 fusion is a consistent finding in chondroid lipomas: a study of eight cases.

Chondroid lipoma of the thigh: a case report.

Intraneural chondroid lipoma on the common peroneal nerve.

Chondroid lipoma:a rare lesion posing diagnostic difficulties .

Chondroid lipoma: an update and review.

Giant chondroid lipoma of breast.

Chondroid lipoma of the tongue: a report of two cases.

Chondroid lipoma of the right thigh: Correlation of imaging findings and histopathology of an unusual benign lesion.

Chondroid lipoma: an ultrastructural and immunohistochemical analysis with further observations regarding its differentiation.

Diagnosis of chondroid lipoma by fine-needle aspiration biopsy.

Lipomatous tumors of the skin and soft tissue. New entities and concepts.

Chondroid lipoma. A newly described lesion that may be mistaken for malignancy.