Malignant Lymphoma with the MRI Findings Mimicking Inflammatory Disease: A Case Report.

Magnetic resonance imaging (MRI) is a more useful diagnostic modality for detecting paranasal tumors compared with computed tomography (CT). We encountered a case of malignant lymphoma of the maxillary sinus. Although CT findings suggested malignancy, MRI findings indicated an inflammatory disease. The patient was a 51-year-old man with a chief complaint of right maxillary toothache. Edema in the right middle meatus and bloody rhinorrhea were observed. CT revealed r ight maxillary s inus shadow with partial bone loss, suggesting malignancy. However, MRI performed two weeks later showed an internal homogeneous lesion with neither contrast effect, nor invasion outside the maxillary sinus. The patient also had no fever, weight loss, or night sweats. Additionally, no palpable cervical lymphadenopathy was observed. Endoscopic sinus surgery was performed to confirm the diagnosis. Upon opening the maxillary sinus, highly viscous retention and a large amount of yellowish-white debris were observed. Allergic fungal rhinosinusitis was suspected. However, histopathological analysis of the debris established a diagnosis of malignant lymphoma. The debris exhibited pathological findings of necrosis. The patient remained in remission after undergoing radiochemotherapy. Malignant lymphomas of the paranasal sinuses, which have a minimal tendency for invasion but with considerable predominance of necrosis, may be diagnosed as an inflammatory disease, based on MRI findings. In cases in which a thorough physical examination could not rule out malignant lymphomas, an endoscopic biopsy should be immediately considered.