PMC8142272_01
Evolution of bone marrow histology from 1994 to 2019. In 1994, MPN in chronic phase with ET morphology: normocellular bone marrow with enlarged megakaryocytes with hyperlobulated nuclei (A), reactive for CALR immunostaining (B). In 2016, progression to fibrotic phase as post-ET Myelofibrosis: hypercellular bone marrow with dense clusters of atypical megakaryocytes (C), reactive for CARL immunostaining (D). In 2019, APL-blast crisis with hypergranulated promyelocytes (E), staining positive for CALR together with a megakaryocyte (F).
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A 55 years-old male suffering from long lasting chronic non erosive seronegative arthritis without health impairments was diagnosed with ET in 1994 (Fig. 1a) and began treatment with aspirin and hydroxyurea (HU). Revision of bone marrow biopsy at diagnosis confirmed the diagnosis of ET and the second biopsy was referred to a post-ET myelofibrosis, categorized as intermediate-2 risk (MYSEC-PM). (Fig. 1a-d) The patient was managed with warfarin and ruxolitinib (15 mg BID), experiencing a progressive improvement of spleen size, liver impairment, and constitutional symptoms. Conventional cytogenetic and fluorescence in situ (FISH) revealed the presence of t(15;17) (q24;q21) [14]/46, idem, del(9)(q21q32)[3] in 20% of metaphases of analyzed cells (Figs. 1e and 2). Immunohistochemistry was performed on serial bone marrow sections from 1994 to 2019 with a commercial antibody for immunodetection of all CALR mutations in ET and PMF (Anti-CALRmut, CAL2, Dianova Int.): megakaryocytes were positive in all specimens with promyelocytes and immature myeloid precursors staining positive in APL specimen (Fig. 1b-d-f).
Conventional cytogenetic (A) and fluorescence in situ (B) at time of leukemic evolution. (A) G-banded karyotype revealed a reciprocal translocation between the long arms of chromosomes 15 and 17 at 15q22 and 17q21 [t(15;17)] in 20% of metaphases analyzed. An additional cytogenetic abnormality in chromosome 9 was found [del(9)(q21q32)]. (B) Interphase FISH demonstrated a fusion signal pattern of chromosome 15 and 17 in the patient. The PML gene in the chromosome 15 is labelled red, the RARalpha gene in the chromosome 17 is labelled green and the PML-RARalpha is labelled yellow.
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Conventional cytogenetic and fluorescence in situ (FISH) revealed the presence of t(15;17) (q24;q21) [14]/46, idem, del(9)(q21q32)[3] in 20% of metaphases of analyzed cells (Figs. 1e and 2).