The patient is a 20-year male who presented for neck pain 2 weeks after he fell while playing football. Commuted tomography (CT) scans revealed a lytic and expansile lesion of the right lateral C1 vertebrae with a linear fracture (Image 1A). The magnetic resonance imaging (MRI) demonstrated a diffuse signal abnormality consistent with a pathologic fracture (Image 1B). After an inconclusive fine needle aspirate examination, the radiological findings were reviewed, and the lesion was thought to be likely an aneurysmal bone cyst. The vertebral fracture was thereafter repaired with a C3 to occiput fusion (Image 1B, inset) without a hematology referral. Approximately 15 months after surgery, the patient developed intermittent deep groin pain exacerbated by exercise, and the region was further traumatized after a fall in the shower. Radiological evaluation (CT) revealed a large lytic acetabular lesion of right hip (Image 1C) and an additional lytic lesion of the left first rib. The radiological differential diagnosis remained the same, including aneurysmal bone cyst, giant cell tumor, and eosinophilic granuloma. A biopsy of the acetabular lesion unexpectedly showed sheets of abnormal plasma cells (Image 1D1), which were positive for CD38, CD138 (Image 1D2), CD56 and kappa light chain (Image 1D3), but negative for lambda light chain (Image 1D4). The plasma cells were negative for CD19, CD20, and cyclin D1. Fluorescence in situ hybridization demonstrated monosomy 13 in 55% and loss of IGH gene locus in 77% of interphase cells. Subsequent laboratory tests demonstrated serum free kappa light chain (160 mg/dL; reference range, 0.33–1.94) and urine free kappa light chain (Bence Jones protein, 643 mg/dL/24 hr) (Image 1E). Serum β-microglobulin was 2.0 mg/L (reference: <2), and complete blood cell count, renal function and metabolic profile including serum calcium were within normal limit. Bone marrow biopsy revealed no evidence of plasma cell neoplasm. A diagnosis of solitary plasmacytoma of bone was thus established. This patient was treated with local radiotherapy and systemic chemotherapy. He was started on four cycles of RVD (Lenalidomide, Bortezomib, and dexamethasone) and then high dose chemotherapy followed by autologous stem cell transplant, and responded well.Image 1.
Plasma cell neoplasm tends to occur in elderly , and patients younger than 30 years are extremely rare. Although radiographic scans demonstrated evidence of bone lytic lesions in our case, a diagnostic possibility of solitary plasmacytoma was initially overlooked, primarily due to the extremely young age of the patient. It has been reported that patients of 40 years or younger with plasma cell neoplasms frequently present with macrofocal plasma cell myeloma, often preceded by solitary plasmacytoma of bone. Studies have demonstrated a favorable clinical outcome in patients of this age group . This case emphasizes a hematology referral and diagnostic differential of plasma cell neoplasms regardless of patient's age if bone lesions are present.