A Rare Case of Malignant Transformation of Keratinous Cyst in Gluteal Region

Keratinous cyst (Epidermoid cysts) is more common and frequently encountered. It is one of the commonest benign lesion. Malignant transformation of keratinous (epidermoid) cyst is very rare. Epidermal cyst is noted as non-malignant condition. Few cases have shown malignant transformation of keratinous cyst into Squamous Cell Carcinoma (SCC). Here, authors report a rare case of 49-year-old male who presented with long standing keratinous cyst in gluteal region which turned out as SCC 35 years after intial presentation of the leison, and here authors have discussed the clinicopathological features of this rare entity. Hence, any swelling which is long standing, showing sudden increase in size, progressing symptoms, more than 2 cm in diameter, cyst content seen as heterogenous pattern on imaging should be highly suspicious of malignancy.