Abstract

Extraskeletal chondrosarcoma is a rare malignant tumor. The well differentiated histological type, which is found primary in soft tissue, is extremely rare. This report describes the case of a
58 year-old woman presented with a large palpable mass in the right buttock. Imaging studies revealed a well-defined soft tissue mass, with extensive calcification. A histological examination after surgical resection confirmed the diagnosis of well-differentiated extraosseous chondrosarcoma. The outcome was favorable, without recurrence or metastasis.

Introduction

Chondrosarcoma, a malignant tumor that originates from cartilage cells, is the second most common malignant bone tumor, constituting 20-27% of all primary malignant osseous neoplasms 1 2. Chondrosarcoma can also develop in other areas, such as soft tissue 3-5, lung 6, breast 7, where cartilage is not normally found. The purpose of this report is to describe a rare example of a well-differentiated extraosseous chondrosarcoma arising in soft tissue and discuss the differential diagnosis of cartilaginous lesions.

Case report

A 58-year-old woman, with no significant past medical history, presented with a 6-months history of a painless lump in the right hip, without sensory or motor deficit or difficulty in mobilization in the physical examination. A radiograph revealed a soft tissue mass, with flaky calcification (Fig. 1). Magnetic resonance imaging (MRI) revealed a well-defined soft tissue mass in the right buttock. The mass mesured 12 cm in diameter and showed isointense signal on the T1-wighted image and heterogeneous high signal intensity on the T2-wighted image (Fig. 2). A surgical biopsy was recommended. The biopsy specimen featured numerous whitish cartilaginous fragments. A microscopical examination concluded to an atypical cartilaginous tumor. The presumptive diagnosis was an extraskeletal chondrosarcoma. Computed tomography (CT) confirmed the presence of a well-demarcated soft tissue mass, with arciform calcification outside the right iliac bone, without obvious absorption or destruction (Fig. 3). The tumor was removed surgically, with wide excision. It consisted of a circumscribed solid mass mesuring 18 × 17 cm with a yellow-white matrix and cartilaginous appearance (Fig. 4). Histologically, the tumor was composed of multilobulated, moderately to mildely cellular cartilaginous tissue with calcification and ossification. Chondrocytes contained occasional hyperchromatic nuclei, with binucleation and a mild atypical nucleus. No mitoses were noted. The cartilaginous lobules were separated by fibrous septa, which were continuous with a myxoid matrix. In addition, tumor proliferation infiltrated adjacent adipose tissue (Figs. 5, 6). Histology favored a diagnosis of a well-differentiated chondrosarcoma completely resected. The patient remained well, with no recurrence or metastasis at a 10-month follow up evaluation.

Discussion

Extraosseous chondrosarcomas are infrequent malignant tumors, which account for less than 3% of all soft tissue sarcomas 1 3. The most common histological types are myxoid and mesenchymal chondrosarcomas. Well-differentiated types are extremely rare, with only a few cases reported in the English literature 3-6 8 9 (Tab. I). A careful examination and radiological assessment should be performed to exclude metastasis. The present case was unusual because the tumor belonged to a well-differentiated subgroup of extraosseous chondrosarcomas and originated in the soft tissue of the buttock.

The most commun presentation of an extraosseous chondrosarcoma is a mass. However, extraosseous chondrosarcoma can reach an enormous size, as was found in the present case. CT revealed an oval-shaped mass, with a ring and arc pattern of chondroid matrix mineralization 3. Histologically, the tumor was composed of multilobulated blue hyaline cartilage. These lobules of cartilage were not well defined. Previous studies reported increased cellularity and atypia, depending on the grade of the tumor 3 5.

Well-differentiated extraskeletal chondrosarcoma generally have a good prognosis after wide excision, although cases of recurrences or metastases have been reported in the literature. For example, Khaldi et al. described a case of a well-differentiated extraosseous chondrosarcoma of the foot, with pulmonary metastases 5. In the present case, the differential diagnoses included a soft tissue chondroma and myxoide liposarcoma, with cartilaginous differentiation. Soft tissue chondromas are rare benign tumors, which occur mainy on hands and feet. They are well demarcated, small masses which rarely exceed 3 cm in diameter, and do not invade adjacent tissue 10. A myxoide liposarcoma with cartilaginous differentiation presents as a well circumscribed, multinodular, intramuscular tumor, with a gelatinous cut surface 11. Histologically, this tumor shows bland fusiform cells and lipoblasts in a myxoide background, with a prominent capillary net work and focal cartilaginous differentiation 11.

In conclusion, extraskeletal chondrosarcoma is a rare malignant tumor. We describe a recent case of well-differentiated extraosseous chondrosarcoma. The current report is unique because of the rare histological type and because only a few cases of extraskeletal chondrosarcoma in the soft tissue have been reported. An extraskeletal chondrosarcoma should be considered as a possible diagnosis, especially when a soft tissue mass shows calcifications on imaging examinations.

Figures and tables

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Tab. I..

Article Year Number of cases Age/Sex Location Size (cm) Tumor grade Follow-up Evolution
Wu et al. 8 1980 5 NA NA NA NA NA NA
Amir et al. 4 1985 1 50/M Foot soft tissue NA NA NA NA
Bailey et al. 9 1990 1 70/F pleural 8 Grade I 13,5 years Alive with no recrrence or metastasis
Khaldi et al. 5 2005 1 38/M Foot soft tissue 7,5 Grade I 4,5 years Alive with pulmonary metastasis
Shah et al. 6 2007 1 60/M Lung 14 Grade I 6 years Alive with cutaneous and vertebral metastasis
Dianbo et al. 3 2011 1 71/M Inter costal soft tissue 9,1 Grade I 1 year Alive with no recrrence or metastasis
Present case 2017 1 58/F Buttock 18 Grade I 10 months Alive with no recrrence or metastasis
Clinico-pathologic features of all well-differentiated extra-osseous chondrosarcoma.