F3Ch24 (104578): This is the same general area as seen in Fig. 2; there is a multi- nucleated giant cell in the center of the field.

F4Ch24 (104578): The pattern of collagen bundles is abnormal. There is one giant cell. Some of the cells below the giant cell are bizarre. The bizarre cells have dendritic qualities and lavender cytoplasm; they are interpreted as dendritic fibroblasts. Some of the smaller cells that appear as “naked nuclei” are interpreted as migratory histiocytes. The nature of the giant cells in an angiofibroma is problematic in the absence of immunohistochemical studies. Some of the giant cells may be fibroblastic giant cells rather than histiocytic giant cells. There is no identifiable papillary dermis. In addition, the pattern of collagen bundles in this portion of the dermis is abnormal.

F5Ch24 (104578): A basement membrane is poorly defined; the basement membrane zone is defined as a band of pallor. Basal cells that abut upon the basement membrane area show irregular zones of cytoplasmic acidophilia. Scattered cells in the superficial unit of the epidermis show dyskeratosis. There is no evidence of a papillary dermis; an abnormal fibrous matrix of interlaced collagen bundles extends to the D-E interface. Many of the cells of a poorly defined basal unit of the epidermis show evidence of dyskeratosis. Perinuclear vacuoles are a prominent feature of the epidermal keratinocytes.

F6Ch24 (104578): At a margin of the lesion, rete patterns are effaced; there are irregular clefts at the dermal-epidermal interface. Abnormal fibrous tissue extends to the dermal-epidermal interface. Vessels are ectatic and there are focal patterns of concentric perivascular fibrosis. Near the bottom of the field, collagen bundles are loosely spaced in a clear matrix. A vessel near the bottom of the field shows concentric perivascular fibrosis. It could be argued that the fibrosing process is initiated at the dermal-epidermal interface and then extends into the reticular dermis. In addition, some degree of collagenolysis at the advancing margin of the lesion appears to be a common feature.