The tumourous form of the calcifying odontogenic cyst is a rare entity and only a small number cases have been described in the medical literature published in English. Our report concerns a 66-year-old patient with a tumourous mass in the maxilla, with clear COC histological features, in addition to an infiltrative growth pattern of the epithelial islands and ghost cells invading the subjacent stroma, oral mucosa and peripheral maxillary bone. Cytoplasmic and nuclear pleomorphism and atypical mitoses were rarely found. An aggressive surgical approach produced a satisfactory result. We have reviewed the literature available in English and compared it with our case.