Cementoblastoma is a rare, benign, expansive and slow-growing, mesenchymal odontogenic tumor. An eight year-old, Purebred Spanish Horse stallion with clinical history of chronic, refractory to treatment unilateral rhinitis and radiologic evidence of a radiopaque mass at the second premolar tooth root underwent intraoral surgery for tooth and mass extraction. The owner did not want to bear the cost of the histopathologic study and the samples were left unattended in a sterile recipient without a fixative solution for six years. Grossly the mass showed a hard consistence, greyish-whitish color and an irregular surface. Histologically, the mass consisted of an abundant deposit of eosinophilic cementum-like organic matrix with frequent basophilic reversal lines and heterogeneous distribution of empty lacunae. Surrounded by this organic matrix there were numerous fungal hyphae positive for Aspergillus fumigatus immunostaining. The final diagnosis was maxillary cementoblastoma with secondary aspergillosis. High-quality information has been obtained from long-time non-fixed tissues.