Cytopathologic features of orbital intraosseous chordoid meningioma: report of a case and distinction from other myxoid/mucoid tumors.

Chordoid meningioma (CM) is characterized by a striking histologic resemblance to chordoma and propensity for aggressive behavior or recurrence (WHO grade II designation). Orbital intraosseous CM is extremely uncommon and only one case report has been documented. A case is presented here in which squash smears of a left orbital tumor in a 53-year-old male revealed small clusters or cord-like structures of bland tumor cells embedded in a myxoid or mucinous background. Whorl-like structures were also identified. The tumor cells possessed uniformly round nuclei with a smooth nuclear outline, fine granular chromatin, and small nucleoli. Occasional intranuclear inclusions, coarse collageneous cytoplasmic filaments were observed. Many spindle-shaped cells with similar nuclear findings were also seen. A cytologic diagnosis of a chordoid meningioma was suggested and histochemical and immunohistochemical studies were conducted on formalin-fixed, paraffin-embedded material. Immunohistochemically, the tumor cells showed diffuse and strong membranous and cytoplasmic staining for vimentin, epithelial membrane antigen (EMA) and faintly reactive with S-100 protein but negative for pan-neuroendocrine markers (i.e., NSE, chromogranin A, synaptophysin), cytokeratin AE1/AE3, smooth muscle actin, D2-40, brachyury or class III beta-tubulin. The proliferative index with MIB-1 was less than 1%. The diagnosis of orbital intraosseous CM was confirmed based on cytopathologic, histopathological, immunohistochemical results, location of the tumor, and the lack connection to the duramater. We demonstrated here for the first time the cytopathological features of intraosseous CM with emphasis on differential diagnostic considerations.