Plasmablastic multiple myeloma presenting as a pleural mass: a diagnostic challenge.

Plasmablastic multiple myeloma (MM) is a rare and highly aggressive variant of MM that presents significant diagnostic and therapeutic challenges. This variant is characterised by a bone marrow infiltration of ≥2% plasmablasts and is distinguished by its atypical pleomorphic morphology, unique immunohistological profile and extensive extramedullary involvement. The anaplastic features of plasmablastic MM can closely mimic those of high-grade lymphomas, leukaemia, non-haematopoietic malignancies and high-grade carcinomas, often leading to initial diagnostic errors. Accurate diagnosis requires a thorough evaluation that integrates clinical history, radiological findings, morphological analysis, immunophenotyping and genetic markers. Here, we present the case of a woman in her early 70s who was diagnosed with high-risk plasmablastic MM. The patient, with no significant neoplastic history, presented with chronic pain and an acute fracture, initially raising suspicion for high-grade metastatic lung carcinoma.