The aim of this article is to report the case of a 23-year-old female patient that sought dental service for examination of an asymptomatic slow-growing large lump in the mandibular gingiva causing displacement of the right first molar. Excisional biopsy, histopathological analysis, Alcian blue/periodic acid-Schiff (PAS) staining and immunohistochemistry analysis for S-100 were performed. The diagnosis established was oral focal mucinosis. After three years, the patient is still under follow-up, without any recurrences. Although cases of oral focal mucinosis of this particular size are rare, this entity should be considered in the differential diagnosis of oral lesions located in the gingiva.5015456Aldred, M.J., Oral focal mucinosis: Report of 15 cases and review of the literature (2003) Pathology, 35 (5), pp. 393-396Gabay, E., Akrish, S., Machtei, E.E., Oral focal mucinosis associated with cervical external root resorption: A case report (2010) Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 110 (4), pp. e75-e78Iezzi, G., Oral focal mucinosis of the gingiva: Case report (2001) J Periodontol, 72 (8), pp. 1100-1102Lee, J.G., Oral focal mucinosis in an adolescent: A case report (2012) Aust Dent J, 57 (1), pp. 90-92Lima, A.A.S., Oral focal mucinosis (2008) Quintessence Int, 99 (7), pp. 611-615Madhusudhan, A.S., Oral focal mucinosis: Report of two cases (2010) Rev Odonto Cienc, 25 (3), pp. 310-313Narayana, N., Casey, J., Oral focal mucinosis: Review of the literature and seven additional cases (2009) Gen Dent, 57 (2), pp. e11-e13Talacko, A.A., Oral focal mucinosis: Report of two cases with ulceration (2004) Pathology, 36 (6), pp. 582-583Tomich, C.E., Oral focal mucinosis (1974) A Clinicopathologic and Histochemical Study of Eight Cases. Oral Surg Oral Med Oral Pathol, 38 (5), pp. 714-724