Basal cell carcinoma.

nodules that reside within the dermis and frequently demonstrate epidermal attachment. Multifocal lobules of varying size and shape exhibit peripheral palisading and central haphazard array of cells.The entire tumor demonstrates an expansile growth pattern. Cystic degeneration or central necrosis may be prominent. Although similar to the nodular variant, micronodular basal cell carcinoma is composed of basal cell islands that are smaller and rounded. Peripheral palisading is less prominent, and the tumor frequently infiltrates throughout the dermis into the subcutis. Local recurrence is more likely, given its propensity for deep invasion. The infiltrating type of basal cell carcinoma is composed of elongated strands of basophilic cells intercalate between collagen bundles within the dermis that lack extensive fibrosis. Jagged or spiking projections may protrude from infiltrating strands. A nodular component is commonly observed in the overlying dermis. This architectural subtype is present in approximately 5% of all basal cell carcinomas. Because of indistinct borders, adequate tumor margins may be difficult to achieve. Stromal retraction and peripheral palisading is frequently absent. Morpheaform basal cell carcinoma is an aggressive histologic variant that accounts for approximately 5% to 10% of all basal cell carcinomas. It is composed of basophilic cells forming narrow strands and small tumor islands that are embedded within a sclerotic dermis. The tumor is poorly circumscribed, with frequent invasion of the deep dermis and subcutis. Keloidal collagen may be prominent. Because the tumor cells permeate the dermis in an infiltrative manner with extensive subclinical extension, margin evaluation may be challenging.