Fibrous hyperplasia is a lesion characterized by the formation of epithelial tissue and fibrous connective tissue in response to chronic trauma or local irritation. It is often located in regions close to the alveolar ridge, cheek mucosa, tongue and lower lip, and may present atypical locations, such as the maxillary sinus. The aim of this study is to report the clinical case of a patient affected by fibrous hyperplasia in the left maxillary sinus, caused by a decompression device. Case report: The patient came to the Oral and Maxillofacial Surgery and Traumatology Outpatient Clinic of the Federal University of Pernambuco complaining of a foul-smelling secretion that came out of the nasal and oral cavities. During the anamnesis, he reported having performed decompression surgery at the affected site approximately seven years ago at another service and, after being discharged from the hospital, he did not return for reassessment. The intraoral clinical examination revealed a hyperplastic, normochromic lesion, involving a foreign body in the left maxillary sinus region. An incisional biopsy of the lesion was performed, resulting in the diagnosis of fibrous hyperplasia. Surgical treatment was recommended, using the Caldwell-Luc technique to access the maxillary sinus region. Surgery proceeded with removal of the foreign body and resection of the lesion. The patient was followed up for 7, 15, 30, 60, 90, 180 days and annually, without signs of recurrence. Conclusion & Significance: The Caldwell-Luc technique allows easy access to the maxillary sinus and its use is frequently described in the literature for the removal of foreign bodies, as well as for the treatment of pathological processes in the region. The patient is under follow-up, with no complaints or episodes of recurrence of the inflammatory process.