BY SEFAKO PHALA; ROBERT STATZ; ANDREW VICTOR; MOHAMMED HASSAN-ALI, MD, MSC; & AHMED RAZIUDDIN, MD
A 65-year-old Caucasian man was brought to the ED via ambulance complaining of worsening upper back pain for one week. His primary care physician had recently prescribed him NSAIDs and muscle relaxants, which failed to provide relief. The newest symptoms were numbness and weakness over his left arm and leg. The patient reported no history of trauma to his back nor did he have any chronic illnesses. Physical exam showed paresthesia in the left upper extremity in a dermatomal distribution pattern that suggested further evaluation in determining the underlying cause of this atypical back pain.
A laboratory workup was ordered including CBC, CMP, TSH, PSA, blood glucose, and urine analysis in addition to a CT scan of the thoracic and lumbar spine. The laboratory results were within normal limits. The CT report of the thoracic spine scan revealed a soft tissue mass associated with a pathologic fracture containing lytic lesions of the T2 and T3 vertebral bodies. An MRI confirmed CT findings alongside additional spinal cord displacement at the level of T2. A differential diagnosis of a single thoracic spinal tumor was made.
CT and MRI images showing vertebral disc lesion at T2 & T3.
The patient was admitted for futher investigation. A full-body bone scan was performed to rule out other lytic lesions. A fine needle aspiration biopsy of the tumor was performed revealing numerous plasma cells consistent with solitary bone plasmacytoma.
Plasma cells within the bone marrow normally produce large volumes of antibodies. (Blood 2003;101:1715.) Born from precursor B cells, the antibodies are released into the blood and lymph with a function to attach to and aid in antigen eradication. Plasma cells play a very important role in the development of several diseases. A plasmacytoma is a localized collection of malignant plasma cells without any proof of a systemic plasma cell disorder. (Blood 2000;96:2037.)
Diagnostic criteria for solitary plasmacytoma of the bone (SPB) include a single area of bone destruction due to clonal plasma cells; normal marrow without clonal disease; normal results on a skeletal survey and MRI of the spine, pelvis, proximal femora, and humeri; no anemia, hypercalcemia, or renal impairment attributable to myeloma; and absent or low serum or urinary level of monoclonal protein and preserved levels of uninvolved immunoglobulins. (Blood 2000;96:2037.)
A study by Hirano (2002) has implicated the overexpression of interleukin-6 in severe autoimmune reactions as well as plasmacytosis with progression to plasmacytoma and multiple myeloma. (Proc Jpn Acad Ser B Phys Biol Sci 2010;86:717.) Moreover, it should be noted that studies have shown progression to multiple myeloma from the initial SPB lesion within two to four years. (Hematology Am Soc Hematol Educ Program 2005:373.)
Bones of active hematopoiesis are the most commonly involved structures of solitary plasmacytoma of the bone. (“Diagnosis and Management of Solitary Plasmacytoma of Bone.” In: UpToDate, Waltham, MA. Accessed March 1, 2016.) Rarely, SPB can extend into surrounding soft tissue. More specifically, bone sites most commonly affected (in descending order) are the vertebrae, pelvis, ribs, upper extremities, face, skull, femur, and sternum. Thoracic vertebrae have higher incidence than lumbar, sacral, or cervical spine vertebrae. Multiple myeloma cannot be ruled out in patients with SPB because of possible undetected immunoglobulin or active focal sites. In fact, M protein is present in 30-75 percent of all cases of SPB. If present, patients have a 50 percent higher risk of developing multiple myeloma and have an overall survival of 10 years. This M protein will not disappear after treatment.
Approximately 450 new cases of SPB are diagnosed each year (0.15 cases/100,000 persons per year; Hematology Am Soc Hematol Educ Program 2005:373), with the highest demographic being blacks, making this case an anomaly. Men are diagnosed almost twice as much as women with median ages ranging from 55 to 65. This patient's family history was unknown, but the condition does have a genetic aspect. An increased risk of plasma cell dyscrasia is observed in patients who have a first-degree relative with monoclonal gammopathy of undetermined significance or multiple myeloma. (“Diagnosis and Management of Solitary Plasmacytoma of Bone.” In: UpToDate, Waltham, MA. Accessed March 1, 2016.)
A full week of diagnostic testing ultimately discovered something far more exceptional than a benign case of back pain. Very little is known about this cancer diagnosis. Advancements in medicine will better characterize and identify medical anomalies such as SPB sooner. The patient is being currently treated with radiation therapy, and is expected to recover successfully.
Special thanks to Manjeet Chawla, MD, of Thorek Memorial Hospital for his contributions to this article.
Mr. Phala and Mr. Victor, clockwise from top left, are fourth-year medical students at the University of Medicine and Health Sciences in St. Kitts. Mr. Statz is a fourth-year medical student at Xavier University School of Medicine in Aruba. Dr. Hassan-Ali is a research assistant at McMaster University in Ontario. Dr. Raziuddin is an emergency physician at Thorek Memorial and Weiss Memorial hospitals in Chicago and at Westlake Hospital in Melrose Park, IL.