Primary extramedullary plasmacytoma of small pelvis

Extramedullary plasmacytoma (EP) is less common form of solitary plasmacytoma. EP can be located in any parts of the body, but the most frequent localization are upper respiratory and gastrointestinal tracts. Primary localization in small pelvis is extremely rare and there are only several cases of EP published. Case report: A 62 years old male patient was hospitalized by an emergency service with complains of oligoanuria, pain in the left groin and leg, general weakness, edema on both legs. The patient had undergone right kidney nefrectomy 5 years ago because of right kidney carcinoma. MRI and CT revealed bulky mass that compressed and infiltrated organs of the small pelvis. Diagnose of renal cell carcinoma was set. Due to atypical clinical course, couple of weeks later it was retested on plasmacytoma CD138 and CD79a markers that were highly positive. No atypical plasma cells were found in bone marrow biopsy. A diagnose was changed to plasmacytoma of the small pelvis, os pubis and inguinal lymph nodes. Before PET scan and chemotherapy patient was tested positive on COVID-19, the treatment had been postponed.Keywords: extramedullary plasmacytoma, multiple myeloma. Primary EP is rare clinical entry. Most of EP of abdomen and pelvis are diagnosed at the stage were bulky local mass is compressing surrounding organs. The main differential diagnosis include other plasma cell tumors, non hematological tumors, metastases. As there are very few cases of pelvis EP localization described and published, there is no guidelines for EP treatment.