Primary chondromesenchymal hamartoma of the orbit.

A 14-year-old girl presented with a 3-month history of proptosis of the left eye. Orbital MRI revealed a superiorly located, well-defined, large mass that was hyperintense on T1-weighted and T2-weighted images with heterogenous internal structure and contrast enhancement. The patient underwent superolateral orbitotomy with bone removal. The tumor was excised totally in a piecemeal fashion. Microscopic examination revealed hyaline cartilaginous nodules admixed with spindle cell stroma and bone formation. Immunohistochemically, the mesenchymal component was diffusely positive for vimentin, smooth muscle actin, and CD34. The cartilaginous nodules and stroma stained with S-100. Based on the histopathologic and immunohistochemical findings, a diagnosis of orbital chondromesenchymal hamartoma was made. The patient has been followed for 6 years with no sign of recurrence. A literature search from 1966 to present using the PubMed database yielded no prior reports of primary orbital chondromesenchymal hamartoma. This case demonstrates that chondromesenchymal hamartoma can occur as a primary orbital tumor in children. Awareness of the presence of this tumor is essential for correct diagnosis.