Parapharyngeal malignant ectomesenchymoma: combined malignant fibrous histiocytoma and primitive neuroectodermal tumour with neuroglial differentiation.

A parapharyngeal ectomesenchymoma consisting of mixed malignant fibrous histiocytoma and primitive neuroectodermal tumour with neuroglial differentiation occurred in a 36-year-old woman. Immunohistochemical and electron microscopic studies verified the combined mesenchymal and neuroectodermal components within the tumour. Only 9 similar cases, including the present one, are on record. The patients ranged in age from 6 months to 49 years, with an average age of 18 years. The male:female ratio was 4:5. The tumour location was widespread. All reported ectomesenchymomas were histopathologically malignant. Recurrence and/or metastasis was/were common. The neural crest has been suggested as the origin of the ectomesenchymomas.