Periapical lesions of endodontic origin are fairly common in the oral cavity in association with tooth pulp infection. Most of these lesions will resolve with adequate root canal treatment and rarely cause suspicion of more insidious disease. Most clinicians tend to skip histopathological examination in cases where the lesion is excised or curetted. We present a rare case of mucinous adenocarcinoma in association an endodontically treated maxillary discoloured central incisor in a 38 year old patient with a history of root canal treatment about 15 years ago. Root canal re-treatment and wide excision was performed. Histology showed epithelial islands suggestive of a neoplasm. Immunohistochemistry was positive for CK7 and S100. Metastasis was ruled out and no evidence of recurrence has been noted in the 12-month follow up period. It is emphasized that any tissue removed from the surgical site should be analysed microscopically. (EEJ-2022-01-013).