Malignant transformation of epidermal cyst is rare, with most cases arising in the head and neck. Here, we report a case of squamous cell carcinoma arising from a longstanding epidermal cyst in the right vulva of a 65-year-old woman. The patient presented with a sudden increase in size of the cyst over 6 weeks to the size of a golf ball. Excisional biopsy and histology indicated moderately differentiated squamous cell carcinoma within an epidermal cyst (FIGO stage IB). Strong p16 immunopositivity was also demonstrated and the potential significance of this is discussed. Limited right hemivulvectomy and right groin node dissection were performed.