Malignant endovascular papillary angioendothelioma (Dabska tumor) arising within a deep intramuscular hemangioma

We report a rare malignant endovascular papillary angioendothelioma (Dabska tumor) arising within the deep periosteal soft tissue of the ulna of an 8-year-old girl. To our knowledge, this is the first report of a Dabska tumor of deep soft tissue that did not extend down from the dermis. This Dabska tumor appears to be a focal change within a larger, well-defined, cavernous hemangioma of deep muscle. We suggest that this represents secondary neoplastic progression of an existing benign lesion, a common phenomenon among vascular tumors. A review of the family of "hobnailed" endothelial cell lesions to which Dabska tumor belongs is presented.