GCBL characteristically has massive epidermal hyperplasia, hyperkeratosis, and parakeratosis and is markedly exophytic. Granular vacuolization may be present, and individual keratinocytes have large cytoplasm and a nucleus with prominent nucleoli. Blunt-shaped masses of tumor project deeply into the dermis and contiguous structures. The tumor cells have little evidence of atypia and are not found inside blood vessels or lymphatics. Individual keratinocytes may show keratinization, but there are no horn pearls.
Lymphohistiocytic inflammation is usually present.
Although the treatment of choice for GCBL is surgical excision, various chemotherapeutic modalities have been used with mixed success as adjuvants to surgery or as treatment for recurrences. The postulated viral origin of these tumors led to the use of interferon with moderate success. One case of vaginal GCBL responded to 6 months of interferon-2 alpha with apparent complete resolution. Traditional systemic antitumor agents also have been used. Autopsy 1 year later showed no evidence of active disease.