Squamous cell carcinoma-like giant keratoacanthoma with delayed presentation in a known case of xeroderma pigmentosum

Abstract Introduction Keratoacanthomas are rapidly growing cutaneous tumours, which usually resolve leaving an atrophic scar. The term ‘giant keratoacan-thoma’ is applied to a lesion greater than 2–3 cm in diameter. This case report discusses squamous cell carci-noma-like giant keratoacanthoma with delayed presentation in a known case of xeroderma pigmentosum. Case report A 50-year-old female patient, a known case of xeroderma pigmen-tosum, presented with a large, dome-shaped, crateriform lesion over her right cheek that had persisted for the last four months. Histological exami-nation showed an exophytic lesion with a large central keratin-filled crater surrounded by deep bulbous nodules of proliferating squamous cells that had abundant keratin with a lip of normal epidermis. The demar-cation was discrete except for tiny foci of deep infiltration at the periphery. However, immunohistochemistry for p53 revealed strong positivity only in the basal layer of the infiltrating islands, weak Ki-67 and desmoglein positivity, along with down regula-tion of Bcl-2 and E-cadherin. Follow-up for 18 months did not reveal any site recurrence or metastasis.