Radiology Resident Case of the Week
Clinical Sx:
39 year old male with history of right posterolateral thigh nevus flammeus ("birthmark" consisting of dilated dermal vessels). Following trauma the patient developed pain and induration in the area of the trauma.
Etiology/Pathophysiology
The patient's nevus flammeus was likely due to a congenital capillary malformation. Trauma, surgery, hormonal swings or hormonal therapy may often cause hemodynamic expansion of previously existing vascular malformations. In this patient, the traumatic event likely caused injury to the abnormal vasculature with thrombosis of a portion of the lesion. This most likely led to altered blood flow and the subsequent development of an AVM.
Pathology:
Analysis of the resected specimen revealed a combined vascular malformation ("hemangioma" and AVM). There was a superficial component of small vessels consistent with a "hemangioma" and a deeper component of larger vessels consistent with an AVM
Miscellaneous
When the true nature of a disease is poorly understood, it is natural for it to be classified by its most salient external features. For this reason, vascular malformations have long been classified by their gross pathologic features, yielding names like strawberry hemangioma, port-wine stain, etc. More recent studies, especially on the pig embryo, have suggested a unitary origin to all arteriovenous malformations.
As primitive mesenchymal blood spaces differentiate, several different stages of development are seen, and depending on the timing of growth arrest or misdirection, anomalous structures with different gross and histologic pathologic features can be identified.
Although several different classification schemes have been proposed, the Mulliken and coworkers classification system has been adopted by the International Society for the Study of Vascular Anomalies. This system, based on endothelial cell characteristics, may be helpful in removing much confusion regarding terminology.
According to this terminology, "hemangioma" should be reserved for pediatric lesions. Two groups of what have been conventionally regarded as "hemangiomas" exist. The first type are characteristically seen at birth and grow commensurably with the patient, possibly changing with changing hemodynamics, lymphatics, or hormonal stimulation. These lesions should be termed vascular malformations. The second category show hypercellularity and increased rate of cell turnover. These lesions appear after birth and show rapid neonatal growth but eventual slow involution (>90% by 5 to 7 years of age). They are truly neoplasms of blood vessels and can truly be termed "hemangiomas". They are nearly always benign. Clinically it is understandably difficult to distinguish hemangiomas from congenital vascular malformations. Large size, fixation to underlying tissues, and visible feeding vessels may suggest a congenital origin, and diminution in size obviously suggests a hemangioma.
Vascular malformations are true congenital structural vascular anomalies resulting from inborn errors (usually non-heritable) of vascular morphogenesis. They consist of high flow malformations to include AVM's and arteriovenous fistulae and low flow malformations consisting of venous malformations, intramuscular venous malformations, lymphatic malformations, and mixed lesions. Presenting complaints can include pain, swelling, induration, intra-articular or skin hemorrhage, peripheral nerve palsy, weakness of the limb, and deformity.
Imaging
The initial ultrasound obtained to distinguish hematoma from solid tumor revealed multiple superficial tortuous vessels, the distal of which were thombosed (in the area of the previous trauma).
An MR subsequently revealed a "cavernous hemangioma" with supply from the profunda femoral artery.
The initial angiogram revealed an AVM with its nidus in the subcutaneous lateral right thigh, supplied by the majority of the lateral branches of the profunda femoral artery and drained by branches into the profunda femoral vein. There was mild dilatation of the profunda femoral artery and mild persistent contrast staining of the AVM.
The lesion was later embolized using 2.5 bottles of 350-500 micron polyvinyl alcohol particles, and post-procedure stasis with embolization of the vast majority of feeders was demonstrated. The lesion was then resected surgically.
DDX
hemangioma, arteriovenous fistula, venous malformation
Key references
1. Robbins, Pathologic Basis of Disease, 5th ed.
2. Yakes, WF, Extremity Venous Malformations, Seminars in Interventional Radiology, DEC 94.
3. Ernst, Stanley, Current Therapy in Vascular Surgery, 899-901.
4. Finn MC, Glowacki J, Mulliken JB, Congenital vascular lesions: clinical application of a new classification, J Pediatric Surg 1983; 18:894-900.
5. Mulliken JB, Young AE edŐs, Vascular Birthmarks: Hemangiomas and Malformations.
ACR Code
923.7171
Keywords:
hemangioma, arteriovenous malformation, AVM, vascular malformation, venous malformation.