Malignant spindle cell neoplasm, unclassified
Malignant spindle cell neoplasms in which not positive diagnostic criteria have been identified. Lesions of this type have traditionally diagnosed as fibrosarcomas or malignant fibrous histiocytomas. Spindle cell carcinomas and melanomas can exhibit morphologies that are indistinguishable from unclassified sarcomas and should be excluded using immunoperoxidase staining. This diagnosis likely encompasses a number of currently unresolvable entities.