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Chondroid Lipoma – Causes, Symptoms, Treatment

Chondroid lipoma is a unique, uncommon benign lipomatous tumor. Due to distinct morphological simply, it is important to distinguish it from extraskeletal chondrosarcoma and myxoid/round cell liposarcoma (MRCLS). We report such a neoplasm with a brief review of the literature.

A chondroid lipoma is a rare variant of lipoma and often confused with chondroid tumors such as soft tissue chondroma, extraskeletal chondrosarcoma, and myxoid chondrosarcoma. It consists of two components – adipose tissue and cartilaginous tissue. Differentiating chondroid lipoma from its malignant variants such as extraskeletal chondrosarcoma and myxoid chondrosarcoma is necessary as the treatment modality is more intense and aggressive for the latter.

A chondroid lipoma is a rare fatty tumor of soft tissue usually presenting as a painless mass, occurring in superficial or deeper tissues. Most lesions are situated in the subcutis, superficial muscular fascia or skeletal muscles of the limbs and limb girdles, trunk and head, and neck.[rx] They may reach considerable size, adding to the risk of misdiagnosing them as sarcomas. There is a predilection for adult women but can also occur in the pediatric age group.[rx]

A chondroid lipoma is composed of cartilaginous tissue and mature adipose tissue with features of both embryonal fat and embryonal cartilage [rx]. Histopathologically it has a close resemblance to myxoid chondrosarcoma, extraskeletal chondrosarcoma, soft tissue chondroma, and myoepithelial tumors. Differentiating it from myxoid liposarcoma is difficult as both of them share similar features clinically and radiologically. Hence, microscopic examination is necessary to differentiate a chondroid lipoma from myxoid liposarcoma. Myxoid liposarcoma shows atypical spindle cells, plexiform vascular pattern and shows S100, vimentin, and CD36 positivity. Extraskeletal myxoid chondrosarcoma show hypercellularity and pleomorphism of chondroid tissue with few cells containing intracytoplasmic vacuoles. Soft tissue chondroma is seen in young adults and is usually located in hands and feet and can locally recur. Microscopically, it contains multinucleated giant cells. Myoepithelial tumors are located superficially and show the absence of multivacuolated cells and show keratin, EMA, and smooth muscle actin positivity on Immunohistochemistry (IHC) [rx–rx]. In the present case, atypical spindle cells, plexiform vascular pattern, pleomorphism, intracytoplasmic vacuoles, and multinucleate giant cells were absent, hence this case was concluded as a chondroid lipoma.

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Symptoms of Chondroid Lipoma

These are well-circumscribed and may be encapsulated
Three components are seen in all cases
Mature adipose tissue is interspersed or compartmentalized
Myxoid or hyaline chondroid matrix prominent
Alcian blue and colloidal iron positive
Variable sensitivity to hyaluronidase
Hemorrhage, sclerosis, and calcification may be seen
Vacuolated cells
- Usually in nests or cords
- May be in lacunae
Vacuoles of variable size [rx]
- Cells with fine droplets resemble hibernoma cells
- Cells with large droplets resemble lipoblasts
- The cytoplasm may also be granular or fibrillar
- Maybe glycogen positive
The nuclei are usually oval and regular
- They may be central or peripheral
- The nucleoli are inconspicuous or small
- The pleomorphic nuclei are reported in only 1/20 cases
The mitotic figures are reported in only 1/20 cases

Diagnosis of Chondroid Lipoma

Diagnostic Criteria

Well circumscribed, may be encapsulated
Three components seen in all cases
- Mature adipose tissue may be interspersed or compartmentalized
- Myxoid or hyaline chondroid matrix prominent
  - Alcian blue and colloidal iron positive
    - Vaiable sensitivity to hyaluronidase
  - Hemorrhage, sclerosis and calcification may be seen
- Vacuolated cells
  - Usually in nests or cords
  - May be in lacunae
  - Vacuoles of variable size
    - Cells with fine droplets resemble hibernoma cells
    - Cells with large droplets resemble lipoblasts
  - Cytoplasm may also be granular or fibrillar
  - May be glycogen positive
  - Nuclei usually oval and regular
    - May be central or peripheral
    - Nucleoli inconspicuous or small
    - Pleomorphic nuclei reported in only 1/20 cases
    - Mitotic figures reported in only 1/20 cases

Radiographs showed a bulge soft tissue mass in the right lower thigh having predominantly radiolucent density with multiple chondroid matrix of calcification, but the bone cortex is still intact. An MRI was obtained to further define the extent and nature of the lesion, confirming heterogeneous soft tissue mass in the anterior compartment of the muscle of the right lower thigh which mostly consisted of fat tissue, thick septation and some nodular non-adipose components. T2-weighted images through the tumour demonstrated high signal intensity compared with the signal intensity of fat. Fat-suppressed T2-weighted images through the distal part of the tumour showed suppression of the signal through the central fatty components and lobular high signal intensity component at the peripheral rim. After intravenous administration of gadolinium, the heterogeneous mass showed peripheral enhancement. According to these MRI findings, the diagnosis of liposarcoma was initially suggested. Because the presence of chondroid calcification which was shown on radiographs, and these nodular non-adipose components tend to be a chondroid matrix, the diagnosis of chondroid lipoma was recommended.

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Fine needle aspiration biopsy was then performed. The smear from the biopsy showed chondroid material with sparse spindle cells with mild nuclear atypia. Cytology diagnosis was suggesting for malignancy. Based on clinical, radiological and cytological findings, the patient underwent extensive surgical excision of the tumour.

Pathological examination revealed that macroscopically the tumour was solid, composed of yellow material, which mostly consisted of fat tissue but in the periphery, there were some foci of the white solid area of cartilage tissue. Microscopically the tumour was composed of mature adipose tissue admixed with well-formed lobules of hyaline cartilage. Based on the microscopic findings, a diagnosis of chondroid lipoma was established. Due to its rarity, the slides were sent to the University of California, Los Angeles for a second opinion, and the diagnosis of chondroid lipoma was confirmed. The patient had a good recovery after surgery and did not develop any postoperative complications.

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.