Mesenchymal Chondrosarcoma of the Orbit: Radiographic Appearance and its Correlation to the Histopathologic Characteristics

Abstract

Abstract: : Purpose: To report the radiographic characteristics of two rare cases of mesenchymal chondrosarcoma (MCS) of the orbit and their correlation to the histopathologic findings. Methods: Retrospective case review. The radiographic studies, including computed tomography scans (CT) and magnetic resonance imaging (MRI), of two cases of MCS of the orbit that have not been previously reported were reviewed. Hematoxylin and eosin (H&E) and immunohistochemical stains as well as cytogenetics were used to analyze the histopathology of the orbital specimens. Results: CT imaging revealed well-circumscribed intraconal lesions of 2x2x2.5 cm and 2x2x1.5cm in the right superior-lateral orbit. In one case, the mass eroded the bone of the lateral wall and roof and extended to the superior orbital fissure. Both had multiple hyperintense areas of fine and coarse calcifications. These areas correlated with the intralesional deposits of bone and cartilage observed on the H&E exam. The MRI of one case demonstrated a heterogeneous enhancing lesion which was isointense on T1 and slightly hypointense on T2-weighted images. Intermediate signal intensity of noncalcified components of the lesion suggested a high degree of cellularity which was noted on the histology. The specimens consisted of tan-pink, well circumscribed oval-shaped masses. The H&E evaluation revealed a small round blue cell tumor in one case and a variable cellular spindle cell neoplasm in the other. Both displayed a hemangiopericytic pattern and contained islands of hyaline cartilage, some of which showed endochondral ossification. The immunohistochemical studies were positive for CD99 expression in the cytoplasm of small round cells in one case and S-100 protein as well as CD34 expression in the hemangiopericytic component of the other. Conclusions: The radiographic characteristics of MCS correspond to the histolopathologic findings and differentiate it from other orbital lesions. These findings also correlate well with the histopathological and CT scan findings of the eighteen cases of MCS of the orbit previously reported.

Keywords: orbit • tumors • pathology: human