Plasma cell myeloma in a 9-year-old male: Case report and literature review.

Plasma cell myeloma (multiple myeloma) is the most common form of plasma cell neoplasm. It is a rare entity in young patients. The peak incidence is in the seventh decade, with less than 2% of cases occurring in patients under the age of 40. A male patient aged 9 years old with a progressive pain in lower back for about 1 month, aggravated by bending, associated with inability to stand upright, no any history of trauma. He complained about left pin-point chest pain, no any history of febrile illness. MRI showed a mass lesion of the L3 vertebra; CT scan revealed osteolytic lesions in the left T12, S2-sacral region, and left calvarium. Histology report of L3 lesion revealed cells with an eccentric nucleus, prominent Golgi apparatus and Flow cytometry revealed cells stained positive for CD 138 and CD56 and negative for CD45 expression. In situ hybridization identified k-light chain band restriction. Bone marrow evaluation was normal. A small serum monoclonal immunoglobin A spike of k-light chain type was noted. Other tests like complete blood count, lactate dehydrogenase levels, renal functional tests, and B2-microglobulin were normal. A diagnosis of plasma cell myeloma was made and the patient was started on emergent radiation to L3 lesion due to progressive neurological symptoms followed systemic therapy which resulted int reduction of L3 lesion. Plasma cell myeloma is extremely rare form of liquid tumor in the pediatric population, and it is important for any destructive bony lesion in a child to have appropriate work up.