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.