PMC9159834_01
Computed axial tomography (contrast phase). (a) Sagittal section shows an increase in soft tissue volume in the mammary region of the L4 vertebral body. A hypodense lesion with continuity loss is seen at the posterior vertebra wall suggestive of erosive injury (arrow). (b) Cross section at the abdomen shows the spleen with granular characteristics and heterogeneity of its content. (c) In the thorax, abundant granular tissue is observed not only at the rib cage but also in the anterior and posterior mediastinum, secondary to the substance dissemination and infiltration.
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Moreover, evidence of splenomegaly in the absence of tumor disease and lytic lesions is found in the L4 posterior wall (Figure 1).
Renal biopsy immunohistochemistry. (a) In the microphotograph with HyE, we can observe part of the medulla composed by tubules with acute tubular necrosis and disappearance of nuclei in a few cells. The interstitium is altered by the presence of the chronic lymphoplasmacytic infiltrate, arranged by cumulus in some areas, but also the presence of slight fibrosis. (b) Masson staining shows interstitial thickening secondary to the lymphoplasmacytic infiltrate reaching the proximal contoured tubules giving an irregularity in its contour. As a paramount feature, the presence of eosinophilic inclusions (arrowhead) in the cytoplasm of the epithelium covering these tubules is seen and also the desquamation of this epithelium which is compatible with LCPT (arrow). Blue staining confirms the presence of slight fibrosis. (c) Immunohistochemical staining for CD138 (plasma cell biomarker) was performed with a significant reaction at the membrane level highlighting the abundant presence of plasma cells. (d) Reaction to kappa light chains (brown staining) shows variable positivity inside the cytoplasm of plasma cells at the interstitium, which represents its monoclonality.
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