PMC6732638_01
(a) MRI at diagnosis. (b) CT scan at diagnosis. (c) Follow-up MRI after two courses of bortezomib, thalidomide, and dexamethasone. (d) Follow-up MRI after two courses of lenalidomide maintenance.
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fig1
An MRI was performed (Figure 1(a)), revealing a voluminous left extraparenchymal posterior fossa tumor, complicated by occipital osteolysis and hydrocephalus, without distant metastatic lesions. Computerized tomography (CT) scanning revealed no other suspicious lesion (Figure 1(b)). After two cycles, MRI showed regression of the plasmacytoma, which was considered complete (Figure 1(b)). After two courses of maintenance, MRI revealed a net decrease of the extraparenchymal posterior fossa tumor, with a greater necrotic aspect and less enhancement (Figure 1(c)).
(a) Neoplastic plasma cell proliferation. Hematoxylin-eosin-saffron (HES) coloration, x400 magnification. (b) Monotypic plasma cell proliferation. Anti-kappa antibody, x400 magnification. (c) CD138 expression by plasma cells. Anti-CD138 antibody, x400 magnification.
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fig2
Histological examination of the biopsy supported a diagnosis of plasmacytoma (Figures 2(a)-2(c)), revealing the following atypical plasma cells proliferation markers: CD38+, MUM-IRF4+, positive expression of kappa-free light chain (KP-53 clone) without expression of lambda-free light chain (K22-Y clone), CD20-, CD3-, and proliferation index ki67 of 5%.