Spindle cell hemangioma, epithelioid hemangioma

Spindle cell hemangiomas (SCH) are benign vascular tumors that are composed of a mixture of cavernous blood vessels and Kaposi’s sarcoma-like spindle cells. These tumors are rare and typically occur in children and young adults. They may occasionally be associated with other diseases, e.g., an association with Maffucci syndrome, Klippel-Trénaunay syndrome, venous malformations, varicosis or congenital lymphedema has been described.

Typically, SCHs occur on the distal extremities, but much less frequently they are also found on the proximal extremities, on the trunk or in the head and neck region. Clinically, very superficial, slow-growing, non-painful, solitary red-bluish nodules are seen. Occasionally multiple nodules are also found. The size varies from a few millimeters to 10 cm, but SCHs are usually smaller than 2 cm.

Histologically, nodules in the dermis and subcutis develop, sometimes in the deep soft tissue as well. SCHs are well defined but not encapsulated. As well as dilated cavernous blood vessels that are sometimes filled with blood, accumulations of spindle cells can typically be seen. Within the cavernous portions, thrombi or phleboliths may also be present. The endothelial cells are sometimes vacuolized ("blister cells"). The spindle cell segments have branching, narrow vascular clefts. The nuclei of the spindle cells are longitudinally oval, the cytoplasm is eosinophilic. In half of the cases residual blood vessels are still found in the periphery of the lesion, as an indication that the spindle cell hemangiomas are partially or completely intravascular. Immunohistochemically, the cells lining the vascular columns express VWF, CD31 and CD34. Spindle cells, on the other hand, are negative for these endothelial markers, occasionally showing a patchy, variable expression of actin.

The exact origin of SCH is not known, but a neoplastic, malformative or hamartomatous etiology is being discussed. After local excision, a recurrence occurs in up to 50–60% of cases, probably due to intravascular spread. Metastases have not yet been described.

Epithelioid hemangiomas are also mostly benign vascular neoplasms which are typically conspicuous by their regular formation of blood vessels. They typically occur on the head, especially on the forehead, the preauricular region and scalp as well as on the distal extremities, mainly on the fingers. Epithelioid hemangiomas can also occur in bone and deep soft tissue, but it is still unclear whether the biological behavior is identical in these localizations.

Typically, the lesions are subcutaneous (dermal and very deep-seated variants are very rare) and between 0.5–2 cm in size; only rarely do they grow to up to 5 cm. Clinically relatively sharply defined unspecific nodules can be seen.

The histologic appearance is of a relatively sharply defined proliferation of capillary-like blood vessels, which are lined by plump, epithelioid endothelial cells. The well-developed cytoplasm is amphophilic or eosinophilic, sometimes also vacuolated. The cells have a large nucleus with a prominent nucleolus. The vessels are surrounded by normally developed myopericytes. A lumen is not always visible, but usually a small artery is associated with the lesion. In addition, eosinophilic granulocytes and lymphocytes are found in a large number of cases, sometimes with formation of lymph follicles. Immunohistochemically, the epithelioid, endothelial cells are positive for the antibodies CD31, CD34 and ERG. The intact myopericyte layer can be detected with smooth muscle actin.

The recurrence rate after local removal is relatively high at more than 30% of cases. A locally aggressive behavior is very rare.