When Chordoma Isn’t Chordoma: Lessons from a Misleading Diagnosis

Abstract

Primary bone malignancies are exceptionally rare, and sacral tumors often pose significant diagnostic challenges because of their insidious presentation and overlapping radiological features. Chordoma is the most common malignant tumor of the sacrum, while solitary plasmacytoma of bone (SPB) is much rarer and even less frequently considered in Asian populations. We report the case of a 50-year-old man who presented with a one-year history of progressive low back pain, without neurological deficit or systemic features. Initial imaging demonstrated a destructive lytic lesion of the sacrum with an associated soft tissue mass, radiologically suggestive of chordoma. Fine-needle aspiration cytology was inconclusive and yielded conflicting impressions, including Ewing’s sarcoma and chordoma. Definitive biopsy, however, revealed sheets of plasmacytoid cells with Russell bodies and amyloid deposits, establishing the diagnosis of plasmacytoma. This case highlights the diagnostic dilemma posed by solitary sacral lesions and emphasizes the importance of histopathological confirmation, as management of plasmacytoma differs substantially from that of chordoma. Recognition of this rare entity is crucial to avoid unnecessary surgical morbidity, since radiotherapy remains the cornerstone of treatment for sacral plasmacytoma.

J Dhaka National Med. Coll. Hos. 2026; 32 (01): 34-38