PMC8276173_01
(A) low magnification shows a blastic population with diffuse pattern of growth admixed with a lot of tingible body macrophages and apoptotic debris. (B) High magnification reveals blastic immature promyelocytes with hypergranular eosinophilic cytoplasm, kidney-shaped or lobed nuclei and prominent central nucleoli. Immunohistochemistry shows a diffuse and strong expression of both MPO (C) and CD33 (D) along with very high proliferation index Ki67 (E).
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MPO and CD33, whereas expression of CD117, CD34, CD68RPGM1, CD14, CD13, CD163, CD56, PAX5, CD3, and large-spectrum cytokeratin AE1/AE3 was absent. Molecular analysis of embedded paraffin tissue showed the presence of the t(15;17) PML-RARa fusion gene, confirming the final diagnosis of APL, also defined as a granulocytic sarcoma promyelocytic type, because of its own extramedullary nodal localization ( Figure 1 ).
Genomic PML/RARA breakpoint analysis by long-range nested PCR. (A) Agarose gel electrophoresis of long-range PCR products from bone marrow and lymph node section DNA analysis. (B) Sanger sequencing result of long-range PCR product of PML/RARA genomic amplification derived from BM analysis. Sequence was aligned to the intronic sequences of PML and RARa genes. M, GenLadder 1kb DNA Ladder; BM, bone marrow; LN, lymph node. Arrows indicated the long-range PCR products purified from gel.
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Using different primers combinations, we confirmed the presence of the PML/RARa hybrid that was detected in DNA purified from the lymph node sections ( Figure 2 ). Sanger sequencing of both PCR products showed the same breakpoints locations in the PML and RARa genes, at nucleotide position 996 of the PML intron 3 and position 14392 of the RARa intron 2 ( Figure 2 ).