Features of 18F-fluorodeoxyglucose uptake in multiple myeloma

Background. Multiple myeloma (MM) is a kind of malignancy from malignant plasma cells with high intra- and interpatient variability, because of complex clonal evolution of tumor cells. Positron emission tomography combined with computed tomography with 18F-fluorodeoxyglucose (¹⁸F-FDG-PET/CT) plays a major role in MM visualization, but there are evidences of non-FDG-avid cases of MM. Taking into account the increasing role of ¹⁸F-FDG-PET/CT in MM, special criteria for risk-group stratification was elaborated. These criteria are based on comparison of radiotracer uptake in tumor tissue, mediastinal blood pool and liver.

Objective: the study of ¹⁸F-FDG uptake in MM and solitary plasmacytoma before antitumor treatment to assess the applicability of criteria based on the ratio of activity in tumor tissue and liver.

Materials and methods. We reviewed 65 ¹⁸F-FDG-PET/CT scans of patients with MM and solitary plasmacytoma before treatment.

Results. In our cohort we identified 2 tumor cases of a plasma cell nature, which amounted to 2 % among all B-NHLs. In one case, the process was located in the nasal cavity and clinically manifested itself with nosebleeds. The second case is a lesion of the mouth floor, primarily with the ulcer formation. In the first cases, at diagnosis, the immunohistochemistry (IHC) test was performed after patient’s chemotherapy and radiation treatment, which distorted the tumor immunophenotype. In the second cases with extensive process in maxillary sinuses, a complete and very detailed IHC test was carried out; however the data did not allow for a definitive diagnosis. Difficulties apparently arose in the interpretation of CD38 expression – main marker of plasmacytic line cells, as well as due to the unusual morphology.

Conclusion. Therefore, 5-point scale is eligible for MM tumor assessment in 52 % of patients and feasible in 32 % of patients, but in 16 % patients alternative criteria are required.