First Reported Case of Extramedullary Plasmacytoma of the Appendix

Abstract

An extramedullary plasmacytoma involving the gastrointestinal tract is extremely rare. We report an appendiceal extramedullary plasmacytoma in a 35-year-old man who presented to the emergency department because of upper abdominal pain. Computed tomography (CT) imaging revealed an incidental mass (3.7 × 1.9 × 1.6 cm) at the tip of the appendix. Microscopically, the appendix, periappendiceal soft tissue, and nearby lymph nodes were diffusely infiltrated by plasma cells that were kappa light chain restricted. Subsequent workup included an unremarkable bone marrow biopsy, as well as urine and serum electrophoresis. A diagnosis of kappa-restricted solitary extramedullary plasmacytoma was made. To our knowledge, this is the first case reported of an appendiceal extramedullary plasmacytoma in the medical literature.

Keywords: Appendix; Extramedullary plasmacytoma; Gastrointestinal tract; Plasma cell neoplasm.

Figure 1

Abdominal CT imaging demonstrated a 3.7-cm mass at the appendiceal tip (arrow). CT: computed tomography.

Figure 2

(a) The appendiceal wall was infiltrated by a plasma cell neoplasm (hematoxylin and eosin staining, × 400, plasma cells indicated by blue arrow). (b) The cells were positive for cluster of differentiation 138 (CD138) (anti-CD138 immunohistochemistry, × 400, positive cells indicated by green arrow). (c) The cells also demonstrated prominent kappa light chain restriction (kappa in situ hybridization, × 400, positive cells indicated by yellow arrow).