Histopathology, mTOR activation, and SVEP1 in iMCD-TAFRO. (A) Reactive follicular and paracortical hyperplasia (original magnification, ×20); scale bar, 500 μm. (B) Concentric mantle zones (arrowhead), regressed follicle (long arrows), and increased vascularity (arrows; original magnification, ×100); scale bar, 100 μm. (C) Areas with abundant plasma cells are positive for CD138 (original magnification, ×20); scale bar, 500 μm. (D) Plasma cells have mature morphologic features (original magnification, ×400); scale bar, 30 μm. (E) Scattered cells are positive for TdT (original magnification, ×400); scale bar, 30 μm. (F) Flow cytometry shows a population of T lymphoblasts positive for CD34 and CD7 (bright) and dim-to-negative CD2, CD4, and CD5. (G) Expression of pS6, a marker of mTOR activation, in areas with abundant plasma cells (original magnification, ×400); scale bar, 30 μm. (H) ELISA for SVEP1 shows results for controls (Controls), flare (Flare), 4 days after treatment (Treatment Day 4), and during remission (Remission) 6 months later. The biopsy was obtained during a flare.