[1324] Extramedullary Amyloid Deposits Are Frequently Present in AL-Amyloidosis Bone Marrows: Need for Better Definition of Marrow Involvement

Sameer Al Diffalha, Lu Wang, Swati Mehrotra, Maria Picken, Girish Venkataraman. Loyola University Medical Center, Maywood, IL; University of Chicago Hospitals, Chicago, IL

Background: Current literature indicates an increasing need for defining organ specific involvement in patients with amyloidosis. More importantly, not only the presence but also the precise spatial location and the extend of amyloid deposits in the bone marrow has critical implications for diagnostic and therapeutic purposes, especially in patients with AL-amyloidosis. Hence, we sought to characterize the spatial distribution of amyloid in the marrow of AL-patients.
Design: We reviewed 11 patients with AL-amyloidosis (PCD, n=9, chronic lymphocytic leukemia [CLL], n=1 and lymphoplasmacytic lymphoma, n=1) in whom bone marrow core biopsy (BMBX) Congo red (CR) stain was performed. Nine of 11 were diagnostic biopsies, one represented relapsed myeloma and one was a post-treatment marrow. Specific features (marrow plasma cells [PC] percentage, light chain clonality via immunohistochemistry) serum immunofixation and serum free light chain were also correlated. Congo red stain was examined by polarized microscopy and spatial location of amyloid deposits was noted as medullary (stromal vs. vascular) or extramedullary periosseous (EM/PO).
Results: Among these 11 BMBXs (10 lambda;1 kappa, 5 IgG, 2 IgM, one IgA and 3 light chain only cases), amyloid deposits were located within the medullary compartment in 5 BMBXs (see figure 1) while in the other 6 BMBXs (55%) they were present in the EM/PO tissues. In the first group, 3 cases showed isolated marrow stromal deposits, one exhibited vascular deposition, and one showed concurrent stromal and vascular deposits. Concurrent EM/PO and medullary deposits were not observed in any case. There was no significant difference in the median PC counts between the EM/PO and M groups (8% vs 9%, p=n.s., Mann-Whitney test).
Conclusions: Our study shows that there is significant spatial heterogeneity of amyloid distribution in patients with AL-amyloidosis with notable preponderance of extramedullary/periosseous amyloid deposits. These findings raise the need for development of a consensus definition of what constitutes marrow involvement in amyloidosis in general and in AL in particular and how it should be graded.


Category: Hematopathology

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 229, Wednesday Afternoon

 

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