Histopathologic features of lymph node, endoscopic and histopathologic features of esophageal involvement in idiopathic multicentric Castleman disease (A and B) Histologic findings of the right inguinal lymph node revealed marked plasmacytic infiltration in the interfollicular region (HE staining, the bar indicates 200 micro m in A, and 50 micro m in B). (C and D) Immunohistochemistry of the right inguinal lymph node showed CD20-positive B cells within the follicles (C, the bar indicates 200 micro m), and CD138-positive plasma cells were observed outside the follicles (D, the bar indicates 200 micro m). (E) On endoscopy, an 0-IIc-like lesion (approximately 40 x 10 mm) with slightly thick mucosa was observed in the middle part of the esophagus (indicated by arrowheads). (F) Narrow-band imaging (NBI) showed a brownish area in the center (indicated by arrowheads). (G) Magnifying NBI observation revealed mainly type B1 according to the endoscopic classification of the Japanese Esophageal Society. (H) The size of the resected esophageal specimen was 58.5 x 20.3 x 5.4 mm. (I and J) Histologic investigation of the resected esophageal specimen revealed follicular hyperplasia with marked plasmacytic infiltration in the interfollicular region (HE staining, the bar indicates 200 micro m in I, and 50 micro m in J). (K and L) Immunohistochemistry of esophageal specimen showed CD20-positive B cells within the follicles (K, the bar indicates 200 micro m), and CD138-positive plasma cells were observed outside the follicles (L, the bar indicates 200 micro m).