Multiple myeloma (MM) diagnosis requires ≥10% plasma cell (PC) infiltration in the bone marrow (BM), detected by bone marrow aspiration (BMA) or biopsy (BMB). We evaluated the concordance of these 2 techniques in 189 patients. In 43 cases (23%), the techniques were discordant, 10 due to poor sample quality. In the remaining 33 patients, BMB diagnosed MM, while BMA detected <
10% PC, being symptomatic in 16 patients and smouldering (SMM) in 17. Without an initial BMB, 11% would have been misdiagnosed
and 12% of symptomatic patients would require a second BMA or BMB for strict diagnosis according to current criteria.