Tumor remnants within giant cells following irradiation of cutaneous squamous cell carcinoma

BACKGROUND. The histopathologic effects of curative doses of radiation therapy on cutaneous squamous cell carcinoma (SCC) have not been well described in the dermatologic literature. OBJECTIVE. To understand the histopathologic process of cutaneous SCC involution following radiation treatment. METHODS. Hematoxylin-eosin stain and immunoperoxidase stains for keratin were performed on tissue from the site of a primary cutaneous SCC 2 months after completion of fractionated radiation therapy (7000 cGy total) but prior to clinical involution. RESULTS. Histopathological examination of the irradiated SCC revealed dermal keratin pearls and keratinocytic necrosis resembling apoptosis as well as inflammation and foreign body giant cell reaction. Immunoperoxidase staining for keratin revealed cellular remnants of cutaneous SCC without intact keratinocytic nuclei within giant cells. CONCLUSION. Complete clinical resolution of the SCC over the next several weeks without recurrence after 15 months confirmed the histopathologic findings of tumor destruction by primary radiation therapy.