Retroperitoneal extramedullary plasmacytoma: A case report and review of the literature

RATIONALE: The incidence of extramedullary plasmacytoma (EMP) accounts for 3% to 4% of all cases of generalized plasmacytoma. The most common pathogenic sites are the head and the neck. It is noteworthy that the pathogenic site in this case is extraperitoneal, which is uncommon in clinical practice. In this case report, we aim to discuss the clinical features and diagnosis as well as the treatment methods of EMP. PATIENT CONCERNS: A 30-year-old female was admitted to our hospital due to a palpable right upper abdominal mass without symptoms of abdominal pain, diarrhea, constipation, fever, or oliguria. DIAGNOSIS AND INTERVENTIONS: Enhanced CT scan showed a right retroperitoneal mass, which we considered to be isolated fibroma. Multiple myeloma (MM) was excluded through whole-body diffusion weighted imaging (DWI) and bone marrow biopsy. The patient underwent retroperitoneal tumor resection, and the postoperative pathology revealed plasmacytoma. Thereafter, she received only postoperative radiotherapy. OUTCOMES: During the radiotherapy, the patient's condition and appetite were acceptable with I° gastrointestinal reaction. The CT examination of the chest and upper abdomen performed 4, 8, and 12 months after the radiotherapy still showed postoperative and postradiotherapy changes after retroperitoneal plasmacytoma resection without obvious abnormal signs. No recurrence and metastasis were detected after a one-year follow-up. LESSONS: Retroperitoneal extramedullary plasmacytoma (EMP) is a rare condition that is frequently a diagnostic challenge, mainly due to its unusual location and nonspecific symptoms, especially in the early stages. The diagnosis of EMP is made through a combination of imaging and pathological examination. Presently, the combinations of radiotherapy and surgery or radiotherapy are the primary treatments, usually leading to an acceptable local control rate. The application of chemotherapy, however, should be carefully considered.