An autopsy case of an anaplastic xanthomatous tumor involving the pharynx and clivus in a 2 year old girl was investigated ultrastructurally and immunohistochemi‐cally. The tumor was manifested as an epi‐ and subdural mass in the posterior cranial fossa involving the pharynx and clivus. The tumor showed an interlacing fascicular and pleomorphic pattern. The tumor cells contained numerous intermediate filaments, which were mainly tonofilaments, and lipid droplets, but did not have junctional complex. Immunohistochemically, most of the tumor cells were positive for cytokeratin, epithelial membrane antigen and vimentin, and some tumor cells were positive for myoglobin and a‐1 antichymotrypsin, but negative for S‐100, CD‐68 and glial fibrillary acidic protein. These findings suggest that this tumor was derived from epithelial cells, and showed xanthomatous appearance. A discussion of its differential diagnosis was