Intravascular schwannoma.

Schwannoma is defined as a benign nerve sheath neoplasm of Schwann cell origin. Cutaneous schwannoma typically manifests along the course of peripheral nerves as a solitary, well-defined, skin-colored nodule within the deep dermis or subcutis of the flexor aspects of the extremities. Schwannoma enlarges slowly and typically follows a benign course, with local recurrence and malignant transformation being exceedingly rare. Although involvement of the vasculature by neurofibroma has been rarely reported, intravascular schwannoma has not been documented to date. We present a unique case of cutaneous schwannoma, as confirmed by histological morphology and immunohistochemistry, within the dermal venous system. Presentation of this case is followed by a discussion of the differential diagnoses of schwannoma, the possible etiologies of the extension of this lesion into the vasculature, and the significance of such a phenomenon.