PMC5993356_01
(A) MRI of lumbar spine showing multiple foci of decreased signal most pronounced at L4 (arrow) (B) Hematoxylin and Eosin stained section of L4 biopsy, 20x (C) MPO immunohistochemical stain on L4 biopsy, 20x (D) Fluorescence in situ hybridization showing PML-RARalpha fusion in L4 biopsy orange = PML Green = RARalpha.
gr1.jpg
PMC5993356_01_gr1.jpg
f0005
The radiographic findings were highly suspicious for metastatic osseous disease (Fig. 1A). A CT guided biopsy of the L4 lesion revealed atypical cells with monolobated or bilobed nuclei and abundant eosinophilic cytoplasm (Fig. 1B). Immunohistochemical stains were performed; the cells expressed MPO (Fig. 1C), lysozyme and CD68 while CD117 was negative. In light of this finding, FISH was retrospectively performed on the L4 biopsy and showed PML-RARalpha fusion in 79% of cells (Fig. 1D) and a diagnosis of APL was made.