Hemangiomas versus arterio-venous malformations: role of elastic stains and mast cell density

Vascular anomalies present diagnostic challenges to histopathologists. Mulliken and Glowacki's classification categorizes vascular lesions into hemangiomas and vascular malformations.

This study explored diagnostic clues in the histomorphology of hemangiomas and vascular malformations.

A total of 120 cases of benign vascular lesions were retrieved from 12 years period. A total of 94 cases, where complete clinical details and representative paraffin sections were available, were included in this study. Hematoxylin and eosin (H and E) stain and Verhoeff's stain for elastic tissue were done on all cases and lesions were classified into hemangiomas or arterio-venous malformations (AVM). Mast cell density in all lesions was calculated from toluidine blue stained sections.

Ten cases of hemangiomas were reclassified as AVM on the basis of presence and absence of arteriovenous structures. Intra-lesional nerves were seen in significantly higher number of AVMs compared to hemangiomas. Medium and thick sized nerve bundles were seen in 56% of AVMs, while they were not seen in any of the hemangiomas. Mean mast cell density was significantly higher in proliferating hemangiomas (53.12 ± 27.83 cells/mm2) compared to involuting hemangiomas (11.43 ± 7.9 cells/mm2).

Use of elastic tissue stains are useful ancillary tools to distinguish between AVMs and hemangiomas. The presence of arteries and arterioles are an integral part of AVMs. The presence of the intra-lesional nerves can be useful to distinguish between AVMs and hemangiomas even on H and E stained sections. The significantly higher mast cell density seen in proliferating hemangiomas compared with involuting ones, seem to suggest that mast cells play an important role in the natural history of these lesions.