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Acute Panmyelosis with Myelofibrosis

Posted on January 21 2014

Acute Panmyelosis with Myelofibrosis
Case study

Acute panmyelosis with myelofibrosis is rare and typically presents to pathologists with morphologic features resembling a fibrotic stage of primary myelofibrosis or end-stage of myelproliferative neoplasia-NOS, sometimes resembling acute megakaryoblastic leukemia.

However, as in this case, an acute clinical presentation, peripheral smear morphology, and absence of splenomegaly argue against a chronic myelproliferative neoplasm. In this case, diagnosis is further supported by negative testing for JAK2 mutation V617F and BCR-ABL/ t(9;22). The relatively low blast count argues against acute megakaryoblastic leukemia.

The WHO classifies acute panmyelosis with myelofibrosis with acute leukemias, partially due to its rapid course and poor prognosis. However , the disease sometimes presents with only a mildly increased CD34+ blasts. In cases with low blast count, it seems reasonable to view acute panmyelosis with myelofibrosis as a high grade myelodysplastic syndrome with significant risk for acute leukemic transformation. In this case, deletions 5q, 7q, and 20q with coincident complex chromosomal changes support that notion.

History

An 83 year-old male, who had normal CBC findings three months earlier, developed rapidly evolving pancytopenia with no evidence of splenomegaly or adenopathy.

Microscopy

Peripheral smear
M
orphology revealed only minimal red cell abnormalities with rare tear drop cells. Notably, leukoerythroblastocytosis was not seen.

Bone marrow
was hypercellular with striking megakaryocytic hyperplasia and fibrosis,
averaging approximately 85-90% cellularity. Reticulin staining confirmed extensive, severely increased fibrosis. Paraffin immunostaining revealed no increase in CD34+ blasts.

Special Studies

Flow Cytometry
Revealed a mild increase in phenotypically normal myeloblasts (2.2%) without aberrant blast or myelomonocytic antigen staining in a markedly hemodilute sample.

Cytogenetics
Revealed a stemline with deletion of the long arm of chromosome 20 and a sideline with deletion 20q PLUS deletion of 5q; deletion of 7q; derivative 12 resulting from translocation between 12p and 3q; monosomies 9, 11, 13, 18, and 20; and one to four unidentified marker chromosome.

Molecular Diagnostics

Testing for BCR-ABL/ t(9;22) by FISH was NEGATIVE

Real time PCR for JAK2 mutation V617F was NEGATIVE

Differential Diagnosis

Acute panmyelosis with myelofibrosis vs. chronic myeloproliferative neoplasm vs. acute megakaryoblastic leukemia

References

Orazi A et al. (2005) Acute panmyelosis with myelofibrosis: an entity distinct from acute megakaryoblastic leukemia. Mod Pathol. May;18(5):603-14.

Fig 1. Mild red cell changes with few tear drop cells and no leukoerythroblastocytosis Fig 2. Hypercellular marrow with striking megakaryocytic hyperplasia
Fig 3. Severely increased reticulin fibrosis Fig 4. Paraffin CD34 staining shows no increased blasts

 


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