Vertebral compression fractures in elderly patients are commonly attributed to osteoporosis, but pathological fractures from underlying malignancy must always be considered. Plasma cell neoplasms can initially present as solitary plasmacytomas of bone, which may be the first manifestation of systemic multiple myeloma. Early recognition and biopsy are essential for accurate diagnosis and timely management.

A 66-year-old woman presented with progressive lower back pain for two weeks without trauma. Pain was mechanical, worsening with movement, and limiting daily activities. She denied fever, weight loss, night sweats, or neurological symptoms. Examination revealed no motor or sensory deficits.

Radiographs showed a T11 compression fracture, confirmed on computed tomography with features suggestive of a pathological fracture. A transpedicular biopsy of T11 revealed a monotonous infiltrate of atypical plasma cells with eccentric nuclei and clumped “clock-face” chromatin. Immunohistochemistry demonstrated strong diffuse expression of CD138 and MUM1, confirming plasma cell lineage and supporting a diagnosis of solitary plasmacytoma of bone. Subsequent bone marrow aspiration and trephine biopsy revealed clonal plasma cells with immunoglobulin G (IgG) kappa light chain restriction, establishing IgG kappa multiple myeloma with vertebral plasmacytoma.

The patient was referred for systemic therapy, including chemotherapy, with planned follow-up imaging to monitor disease response and prevent further skeletal complications.

This case emphasizes the importance of maintaining a high index of suspicion for malignancy in elderly patients with vertebral fractures. Radiological findings alone may not distinguish osteoporotic from pathological fractures, making biopsy and systemic evaluation critical for diagnosis and management. Early identification of underlying multiple myeloma allows timely oncological intervention, improving prognosis and reducing complications.