Mesenchymal chondrosarcoma--a case report.

S Tyagi, V Maheshwari, N Tyagi 
 Department of Pathology, Jawharlai Nehru Medical College, Aligarh Muslim University.

Correspondence Address:
S Tyagi
Department of Pathology, Jawharlai Nehru Medical College, Aligarh Muslim University.

Full Text

::   Introduction

Mesenchymal chondrosarcoma (MCHD) was first described by Liechtenstein and Bernstein[1] in 1959 as a special variant of chondrosarcoma. This tumour has got a characteristic histological dimorphic.picture, sheets or cords of undifferentiated small round stromal or mesenchymal cells interspersed with islands of well-differentiated cartilage. According to Mirra[2] MCHS is a rare tumour occurring commonly in the 3rd decade. Sometimes, it may involve the extraosseous structures like the orbit, dura, trunk, retroperitoneum and extremeties[3],[4].

During the last 20 years we have come across a single case of mesenchymal chondrosarcoma (extra skeletal). The rarity of the lesion and paucity of the reports in the Indian literature prompted us to publish this case of extraosseous mesenchymal chondrosarcoma.

::   A case report

SA, a Muslim male aged 26 years noticed a gradually increasing mass in the occipital region for the last four years. The swelling was painful and caused discomfort particularly during sleep.

On examination, the swelling measured 10 x 8 x 7.5 cm in size, was soft to firm in consistency and slightly movable. The superficial skin wad denuded at places. On skiagram the growth was free from the occipital bone, sharply or poorly defined with finely stippled or larger areas of mineralization. The tumour was excised and sent for histology.

Gross pathological findings:

The tumour was well circumscribed, lobulated with surface eroded at places and measured 9.5 x 7 x 7 cm. Cut surface was greyish - pink with areas of haemorrhage and necrosis and displayed hard mineralized deposits of variable sizes and foci of definite cartilaginous tissue.

Microscopic findings:

The morphological picture had a characteristic dimorphic pattern, the presence of highly cellular and undifferentiated mesenchymal cells and islands of well-differentiated cartilage (see [Figure:1]). The cellular component in particular was found at the advancing margins of the tumour where lobulation with pushing border was more predominent. The cells were arranged in groups or masses of variable size separated by fibrous septae. The undifferentiated mesenchymal cells were uniform, small with rounded to avoid hyperchromatic nuclei and hardly any cytoplasm. These cells were arranged either in a better-differentiated haemangiopericytomatoid pattern around thin walled blood vessels. (See [Figure:2]) or less differentiated form in diffuse sheets or masses. There were areas of necrosis and haemorrhage in the cell masses. Pleomorphism was less evident and the mitoses were sparse. Intermingled with the mesenchymal cells were the numerous areas of chondroid element, which contained homogenous matrix with regular and small hyperchromatic nuclei (See [Figure:3]). Here also the plemorphism was less marked to what one except in a case of ordinary chondrosarcoma.

At most of the places the two components were welidemarcated, however, at times gradual transition between cellular and cartilaginous components could be visualized. Calcification of the chondroid element was a common feature. Osteoid formation was seen in the tumour as a metapiastic process in a well-differentiated cartilaginous area or as a reactive phenomenon in the adjacent areas surrounding the tumour. Reticulin stain revealed the presence of reticulin fibres around the blood vessels and they either encircled the groups of undifferentiated cells mostly or at times they surrounded the individual cells.

::   Discussion

The salient feature of the case under review was the occurrence of a mesenchymal chondrosarcoma in the occipital region of a boy of 26 years, the histological picture showing a dimorphic pattern comprising of undifferentiated mesenchymal cells and islands of chondroid. MCHS is a very rare tumour, approximately 20.2% of all the primary bone tumours [2]. MCHS can arise in bones or in extraosseous tissues. Huvous et al[4] have reported 14% cases occurring in extraosseous tissues like upper arm, para-spinal soft tissues, inguinal region, thigh and lower leg.

The tumour is much more common in the 2nd decade[3],[5],[6] or in the 3rd decade (3%) as reported by Mirra[2]. Size of the tumour varies from 4 to 30 cm (average 12.5 cm). In the present case the size of the tumour was 9.5 x 7 x 7cm.

MCHS has got a very distinctive histomorphological picture. On the basis of the morphology these tumours are generally divided into two varieties - haemangiopericytomatoid variant as was seen mostly in this case and the less differentiated small cell type. MCHS is to be differentiated from other soft tissue sarcomas namely malignant haemangioperictoma, chondrosarcoma and synovial sarcoma. Focal chondroid and osseous metaplasia can be seen in haemangiopericytoma, however, the uniform distribution of cartilaginous tissue along with undifferentiated mesenchymal cells favours the diagnosis of MCHS. In ordinary chondrosarcoma the cartilagenous component is more pleomorphic and cellular with bizarre nuclei and mitoses. Dual epithelial and spindle cell elements are characteristic of synovial sarcoma.

Genesis of the tumour is obscure. However, the transition areas between the spindle shaped mesenchymal cells and cartilage islands clearly indicate that the tumour takes its origin from the precartilage mesenchyme. Ultrastructural evidence confirms its cartilagenous origin[7].

Surgical resection and radiation therapy to the tumour bed is recommended where the tumour is resectable[3]. Combination chemotherapy is the treatment of choice who had recurrent lesions or in the cases with more anaplastic small cell pattern.

MCHS carries a poor long-term prognosis in comparison to ordinary chondrosarcoma. Metastases may develop and multiple bones may be involved[2]. The medium survival rate was 37.9 months in the series of 32 cases[3]. The present patient remained well even after two years of the operation.

References