Histopathology of PCT. (A) Mesenteric lymph node containing a plasmacytic PCT. Residual follicles, such as the one indicated by arrowheads, are displaced by large interfollicular expansions of mature plasma cells. (B) High-power view of the interfollicular area containing aberrant, yet relatively small, plasma cells with varying amounts of cytoplasm. (C) Small bowel mucosa harboring a plasmablastic PCT with sheets of abnormal plasma cells infiltrating the mucosa. (D) High-power view showing atypical, large plasma cells with pleomorphic nuclei, prominent nucleoli, and varying amounts of cytoplasm, consistent with the diagnosis of plasmablastic PCT. Original magnification: ×4 (A,C) and ×40 (B,D). Final magnification: ×10 (A,C) and ×100 (B,D).