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ICAR SINONASAL TUMORS

2 Workup Traditional X-ray methods have largely been supplanted by cross-sectional imaging modalities such as CT and MRI, as these are superior in assessing the extent of local dis ease and excluding distant lesions. On CT imaging, EMPs often appear as solitary enhancing soft tissue lesions. There may be local remodeling of adjacent bone or lytic bone destruction consistent with its malignant nature. 1872 On MRI sequences, EMPs are generally isointense to muscle on T1, are iso- to hyperintense on T2, and enhance het erogeneously with gadolinium-based contrast. 1873 Areasof necrosis, vascular encasement, or infiltration of adjacent structures may be seen. CT and MRI serve complemen tary roles as CT is better able to delineate bony anatomy and areas of erosion or dehiscence, whereas MRI pro vides superior soft tissue definition and can assist in distinguishing areas of tumor from inspissated secretions and surrounding anatomical structures. However, imag ing alone is often insufficient to reliably distinguish EMPs from other SNM and histology is required to make the diagnosis. Nuclear studies also play a useful role in the evalua tion of EMPs. Although the use of gallium and thallium radioisotopes has been described previously, 1874 recent interest has centered on the use of PET fused with CT (PET–CT). These are useful in confirming the diagnosis of EMP by excluding distant lesions and were proposed as an alternative to whole-body MRI by the IMWG in 2017. 1875 PET–CT was found to be the imaging technique with great est sensitivity and specificity for detecting clonal plasma cells, particularly outside the bone marrow. PET–CTs could yield prognostic information based on the degree of 18-FDG uptake, and are also useful as follow-up studies to assess treatment response. 1876 Laboratory tests are required in the diagnostic process to exclude other diagnoses on the plasma cell dyscrasia spec trum. All patients suspected of having EMPs should have a bone marrow aspiration and trephine biopsy that uses a wide caliber needle obtaining a greater sampling. Serum and urine protein electrophoresis are helpful in evaluating an “M” spike that indicates monoclonal paraproteinemia. Its persistence after initial treatment indicates a poorer prognosis. 20 Immunofixation electrophoresis can provide further specific information on the type of “M” protein and can be used to monitor patients for posttreatment response or relapse. Serum free light chains can also be quantified and serve a similar role. 1877 Histopathological analysis of biopsy specimens often reveals a monomorphic population of neoplastic plasma cells, which may have eccentric nuclei with chromatin arranged in a “cartwheel pattern,” 1878 cytoplasmic per inuclear hof, and abundant basophilic cytoplasm. 1857

Immunohistochemical staining is positive for CD138 (a protein specific to differentiated plasma cells) and epithe lial membrane antigen and negative for CD45 (marker for hematopoietic cells) and CD20 (B-cell marker not found on plasma cells). Neoplastic cells are monoclonal with surface expression of kappa or lambda. These findings help distin guish EMPs from inflammatory processes that may be rich in plasma cells. An anaplastic subtype of EMPs has been described with characteristic increased number of mitotic figures. 1879 It may be difficult to distinguish EMPs from a low-grade BCL with significant plasma cell differentiation. Flow cytometry may be helpful in these cases, as EMPs rarely express CD45 and CD19. 1880 3 Treatment SPs, including EMPs, are radiosensitive, and RT is the primary treatment modality for these tumors. The latest NCCN guidelines recommend upfront RT with 40–50 Gy in 1.8–2.0 Gy fractions. 1881 The evidence for the effective ness of RT primarily stems from retrospective studies, with the largest study showing a 5-year OS rate of 74%, disease-free survival of 50%, and local control of 85%. 1882 Surgery is recommended primarily in the setting of spinal instability or neurological compromise due to mass effect, but these considerations are generally less applica ble to sinonasal EMPs. As part of the diagnostic workup, some patients undergo surgical excision and good out comes have been reported in some instances where nega tive margins have been achieved. 1859,1861,1883 However, this remains controversial as others have found that surgery alone without adjuvant RT leads to poor local control. 1882 Chemotherapy has an uncertain role due to mixed evi dence for its effectiveness. While some studies suggest that adjuvant chemotherapy could delay progression to MM, others have shown no benefit. 1876 4 Prognosis and outcomes Close follow-up is required to monitor for relapse and to watch for transformation to MM in those with persistent disease. This should be done initially on a 3- to 6-month basis but can be lengthened subsequently, especially in EMPs due to their better prognosis. 1881 Blood and urine tests for “M” protein are helpful as its disappearance in patients with initially detectable levels gives further confir mation of successful ablation, and its reemergence could indicate relapse. Serial imaging is an important compo nent of surveillance and MRI or PET–CT can be used. This should be performed on a yearly basis, ideally with the same modality that was used to make the initial diagno-