DISCUSSION
We reported a case of malignant lymphoma of the paranasal sinuses. Due to its minimally invasive tendency outside the paranasal sinuses and the predominance of necrosis, it can be misdiagnosed as an inflammatory disease based on the clinical and MRI findings.
MRI is benefical for diagnosing nasal sinus tumors because of its higher-density resolution than that of CT.1 Moreover, imaging tests are useful for diagnosing early-stage malignant lymphomas of the paranasal sinuses because they present with few symptoms. The CT findings of malignant lymphoma include a geographic or moth-eaten pattern of bone destruction with permeative bone processes.2 On MRI, it exhibits internal homogeneity, low- to isointensity on T1, iso- to high-intensity on T2, and faint contrast.3Additionally, low apparent diffusion coefficient (ADC) values on diffusion-weighted imaging are characteristic of malignant lymphoma.4 In this case, CT revealed a moth-eaten pattern of bone destruction; therefore, a malignancy was suspected. However, MRI exhibited nonspecific findings of a malignant lymphoma, and the lesion was confined to the maxillary sinus without mass formation or contrast effect. Therefore, the patient was diagnosed with an inflammatory disease. A radiologist specializing in head and neck regional imaging reinterpreted the MRI retrospectively but did not suspect neoplastic lesions. The lesion had a high ADC value (1.4×10–3 mm2/s). The mucous reservoirs and debris in the maxillary sinus obtained intraoperatively exhibited necrotic findings on histopathology (Fig. 3cd). Malignant lymphoma is typically characterized by diffuse tissue necrosis.5 Since the maxillary sinus lesion was predominantly necrotic, the MRI findings were interpreted as manifestations of an inflammatory disease.
Malignant lymphomas of the paranasal sinuses have a minimal tendency for invasion outside the sinuses but have predominant necrosis, and may therefore be misdiagnosed as inflammatory diseases based on the clinical and MRI findings.