Practical importance of routine paraffin-embedded bone marrow biopsy in multiple myeloma

Paraffin-embedded bone marrow biopsy specimens obtained prior to (37) or after (25) therapy from 62 patients with multiple myeloma (MM) were analyzed with particular reference to infiltration pattern, extent of infiltration, and myeloid to myeloma tissue percentage ratio (MMR) to verify their mutual relationships and clinicopathologic relevance. Fifty-nine biopsies were evaluable for infiltration pattern (diffuse in 27, interstitial in 25, and nodular in 7). Diffuse and interstitial patterns were more common (P less than 0.025) in stage III and stage I patients, respectively. A higher (P less than 0.001) mean serum paraprotein level was found in patients with the diffuse pattern than in those with the interstitial pattern. The average extent of infiltration by myeloma cells in the residual myeloid tissue was higher (P less than 0.001) and a high extent (75% or more) was more frequently (P less than 0.005) seen in diffuse than in interstitial pattern cases. The average MMR value was lower (P less than 0.001) and a MMR value less than 1 was more frequently (P less than 0.005) seen in the diffuse pattern group than in the interstitial pattern group. All these differences were present also when a separate analysis was performed for treated and untreated patients. It seems that a diffuse histologic pattern, as opposed to interstitial, would significantly predict a bone marrow extent of infiltration of 75% or more, a MMR lower than 1, a higher serum paraprotein level, and a clinical stage III. Bone marrow biopsy appears thus to play a role in providing parameters of prognostic relevance in MM also in the course of the disease. Prospective studies are needed to establish whether histologic pattern has an independent prognostic value.