A primary extramedullary plasmacytoma of the tongue base evaluated by diffusion-weighted imaging : a case report and literature review

Primary extramedullary plasmacytoma (EMP) of the tongue base is rare. Diffusion-weighted imaging (DWI) and the apparent diffusion coefficients (ADCs) obtained by magnetic resonance imaging (MRI) may be used to differentiate benign from malignant lesions. No ADCs for an EMP of the tongue base have yet been reported.We report a 67-year-old male who presented with a 1-month history of a foreign body sensation in the pharynx. Physical examination revealed a round mass on the right base of the tongue. MRI showed that the mass was 0.8 cm in diameter. The mass was isointense on T1-weighted imaging and yielded a mixed signal on T2-weighted imaging. The mass was hyperintense on DWI and had an ADC (b=1000 s/mm2) of 1.23 ± 0.316 × 10-3 mm2/s. The mass was strongly enhanced on contrast-enhanced T1-weighted MR images. The mass was excised via suspension laryngoscopy performed under general anesthesia. The immunohistochemical profile of the tumor (positive for CD138, CD79a, IgG, and kappa light chain) and a systemic examination that excluded multiple myeloma both indicated a diagnosis of EMP. A total of 18 EMPs of the tongue base (including our case) have been reported to date in the English-language literature, of which 7 underwent MRI examination. Only one report mentioned the features of T1and T2-weighted imaging: hypointensity was evident on T1-weighted images and slight hyperintensity on T2-weighted images. DWIMRI may help to differentiate malignant from benign lesions in the tongue base. Radiotherapy plays an important role in treatment.