Cytologic Diagnosis of Chordoma in a Peritoneal Effusion: A Case Report

Chordoma, a distinct malignant neoplasm arising from the remnants of the notochord, occurs mostly in patients in the fifth to seventh decade of life. Metastasis occurs in 20-30% of cases. The most common metastatic sites are lungs and, less commonly, other bones and visceral organs. The cytologic features of chordoma in both primary and metastatic foci have been described for specimens obtained by fine needle aspiration biopsy. A few cases have been reported in the sputum and the cerebrospinal fluid. A 57-year-old man presented with metastatic chordoma diagnosed in a peritoneal effusion. Cytospin slides of the effusion showed numerous individual and clusters of polygonal, round epithelial cells with a background of myxoid chondroid substance, which stained metachromatic on Diff-Quik slides. Many diagnostic physaliphorous cells were present and characterized by abundant intracytoplasmic vacuoles of various sizes. The nuclei were monotonous, with minimal anisonucleosis. The nuclei had evenly dispersed chromatin with occasional small, eosinophilic nucleoli. The nuclear membranes were smooth, with focal indentation. The differential diagnosis included an adenocarcinoma and metastatic chordoma. Immunohistochemistry applied to the cell block showed that the neoplastic cells were positive for cytokeratin and S-100 protein. The clinical history with immunohistochemical profiles helped confirm the diagnosis of metastatic chordoma.