Cemento-osseous dysplasia (COD) is the most common benign fibro-osseous lesion of the jaws and generally considered non-neoplastic and self-limited. Here, we present a 30-year old female who noticed a bilateral swelling of her posterior mandible with irregular periapical mineralization and incomplete root resorption on panoramic radiographs. A biopsy revealed florid COD and no further treatment was initiated. 9 years later, she presented with a progressive expansion of her left posterior mandible after being treated for bilateral breast cancer 4 and 8 years before. CT scans showed expansile and densely mineralized lesions in all four quadrants with the left posterior mandible showing a focal penetration of the buccal cortical bone. Biopsies revealed an osteoblastic high-grade osteosarcoma in the left and a COD in the right mandible, notably with cellular atypia in the spindle cell component. The patient underwent segmental resection of the left mandible with clear margins and adjuvant chemotherapy. Subsequent genetic testing identified a heterozygous germline TP53 mutation (p.V173G) which confirmed the clinically suspected Li–Fraumeni syndrome (LFS). 3 years after the resection, the patient is free of disease and the other foci of COD remained stable in size on follow-up imaging analyses. Our case illustrates LFS-related osteosarcoma developing within florid COD. Given the rarity of this coincidence, a causative relation between the two lesions seems unlikely but in patients with tumor predisposition syndromes it might be advisable to closely monitor even benign lesions like COD.

Malignant melanoma of the oral cavity is a rare disease with high lethality, rapid progression and frequently seen lymph node metastases. The clinical appearance of the mucosal melanoma is mostly irregular in shape and dark blue, brown or black in colour. During early stages the lesions are painless with a tendency to spontaneous bleeding. Mucosal melanoma shows expansive and infiltrative growth into neighbouring structures, with the result of bone destruction and loss of teeth. We present a case of a female patient with a primary mucosal melanoma. A local infiltration and invasion of a tooth could be seen. Although many publications deal with oral mucosal melanoma with local destruction of bone, there are no reports on an infiltration into dental roots. Aspects of this unusual infiltration of hard tissues are discussed.