SHM Converge Scientific Abstract ePoster Gallery-Unusual Case of Plasma Cell Neoplasm Masquerading as a Sacral Mass in a 51-Year-Old Male

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This case report describes a 51-year-old man with 1 week of constant back and flank pain, later accompanied by diarrhea, who was found to have an unusual plasma cell neoplasm presenting as a sacral mass. He had a history of fentanyl use and smoking but no major prior medical conditions. Initial workup revealed widespread lytic bone lesions, including skull involvement and diffuse metastatic-appearing disease on imaging. Brain MRI showed extensive calvarial metastases, while abdominal/pelvic CT identified a large right sacral mass measuring 4.9 × 5.4 × 3.9 cm. Spine MRI also showed an acute T12 compression fracture, a remote L5 fracture, and prominent sacral enhancement with borderline cord compression.<br /><br />Fine-needle aspiration of the sacral lesion confirmed plasma cell myeloma, supported by immunohistochemical markers positive for CD138 and CD79a and negative for HMB45. Laboratory findings were consistent with plasma cell dyscrasia, including anemia, elevated lambda free light chain, markedly abnormal kappa/lambda ratio, positive M-protein isotype, hypercalcemia, and mild renal impairment.<br /><br />The report emphasizes that primary malignant tumors of the spine and sacrum are rare and can be mistaken for benign causes of back pain. Plasmacytoma and multiple myeloma should be considered when pain does not improve with conservative treatment. MRI and CT are important for defining tumor extent and bone destruction, while FNA can provide a rapid, minimally invasive diagnosis. Because sacral involvement in myeloma is uncommon, this case highlights the need for high suspicion and prompt imaging. The patient was referred to radiation oncology for further management, with radiotherapy noted as the preferred treatment for localized plasmacytomas.

Asset Subtitle

Martin Nguyen

Meta Tag

Author List Martin Nguyen, Zarpash Babar

Category Clinical Vignettes

Concept Plasma Cell Neoplasm

Concept Sacral Mass

Concept Sacral Tumor

Concept Malignant Sacral Lesion

Concept Back Pain

Distinguished Non-Finalist

Presenter Organization West Virginia School of Osteopathic Medicine

Presenting Author Martin Nguyen

Track Adult

Keywords

plasma cell myeloma

sacral mass

multiple myeloma

plasmacytoma

lytic bone lesions

back pain

fine-needle aspiration

calvarial metastases

radiotherapy

spinal tumor

Plasma Cell Neoplasm

Sacral Mass

Sacral Tumor

Malignant Sacral Lesion

Back Pain