Christine G. Roth

Clinicopathologic analysis of acute myeloid leukemia arising from chronic myelomonocytic leukemia

Acute myeloid leukemia arising from chronic myelomonocytic leukemia is currently classified as acute myeloid leukemia with myelodysplasia-related changes, a high-risk subtype. However, the specific features of these cases have not been well described. We studied 38 patients with chronic myelomonocytic leukemia who progressed to acute myeloid leukemia. We compared the clinicopathologic and genetic features of these cases with 180 patients with de novo acute myeloid leukemia and 34 patients with acute myeloid leukemia following myelodysplastic syndromes. We also examined features associated with progression from chronic myelomonocytic leukemia to acute myeloid leukemia by comparing the progressed chronic myelomonocytic leukemia cases with a cohort of chronic myelomonocytic leukemia cases that did not transform to acute myeloid leukemia. Higher white blood cell count, marrow cellularity, karyotype risk score, and Revised International Prognostic Scoring System score were associated with more rapid progression from chronic myelomonocytic leukemia to acute myeloid leukemia. Patients with acute myeloid leukemia ex chronic myelomonocytic leukemia were older (P<0.01) and less likely to receive aggressive treatment (P=0.02) than de novo acute myeloid leukemia patients. Most cases showed monocytic differentiation and fell into the intermediate acute myeloid leukemia karyotype risk group; 55% had normal karyotype and 17% had NPM1 mutation. Median overall survival was 6 months, which was inferior to de novo acute myeloid leukemia (17 months, P=0.002) but similar to post myelodysplastic syndrome acute myeloid leukemia. On multivariate analysis of all acute myeloid leukemia patients, only age and karyotype were independent prognostic variables for overall survival. Our findings indicate that acute myeloid leukemia following chronic myelomonocytic leukemia displays aggressive behavior and support placement of these cases within the category of acute myeloid leukemia with myelodysplasia-related changes. The poor prognosis of these patients may be related to an older population and lack of favorable-prognosis karyotypes that characterize many de novo acute myeloid leukemia cases.

CD123 immunohistochemical expression in acute myeloid leukemia is associated with underlying FLT3-ITD and NPM1 mutations.

FLT3-ITD and NPM1 mutation testing in acute myeloid leukemia (AML) plays an important role in prognostic risk stratification, especially within the intermediate cytogenetic risk group. Molecular studies require adequate fresh material and are typically performed on a dedicated aspirate specimen, which may not be available in all cases. Prior flow cytometric studies have suggested an association between CD123 overexpression in AML and FLT3-ITD and/or NPM1 mutations; however, the immunohistochemical (IHC) correlate is unknown. We assessed CD123 IHC expression in 157 AML bone marrow biopsies and/or marrow particle preparations, and correlated with the morphologic, immunophenotypic, and cytogenetic features and with the presence of FLT3-ITD and NPM1 mutations. We found that CD123 IHC expression, seen in 40% of AML, occurred across a wide spectrum of 2008 World Health Organization subtypes and was most frequent within the intermediate risk group. As compared with CD123 IHC−AML, CD123 IHC+AML demonstrated higher marrow blast percentages (median 69%), monocytic differentiation (33/63 cases), and CD34 negativity (29/63 cases). Eighty-three percent (25/30) FLT3-ITD-mutated AML were CD123+ (P<0.0001) and 62% (18/29) NPM1-mutated cases were CD123 IHC+ (P=0.0052) with negative predictive values of 95% for FLT3-ITD and 88% for NPM1. CD123 IHC+AML presents with characteristic pathologic features, some of which may be related to underlying FLT3-ITD and/or NPM1 mutations.

Increased numbers of IgG4-positive plasma cells may rarely be seen in lymph nodes of patients without IgG4-related sclerosing disease.

IgG4-related sclerosing disease (IRSD) is a steroid-responsive fibroinflammatory disorder characterized by increased IgG4+ cells. Nodal involvement usually lacks the dense sclerosis seen in extranodal sites, with histologic patterns overlapping with other reactive processes. Twenty-six lymph nodes showing IRSD-related histologic patterns were evaluated for IgG and IgG4 positive cells by immunohistochemistry and correlated with the clinical features. Cases included 7 Castleman disease–like cases (type I pattern), 10 follicular hyperplasia (type II), and 9 plasmacytosis (type III). The mean numbers of IgG4+ cells per high-power field (HPF) were 4.8 (I), 8.4 (II), and 26.6(III), and the mean IgG4/IgG ratios were 0.05 (I), 0.04 (II), and 0.08 (III). Using >50 IgG4+cells/HPF and IgG4/IgG ratio of >0.4 for absolute and relative increases, only 1 case fulfilled both criteria for increased IgG4+ cells, a patient with Hashimoto’s thyroiditis without clinical evidence of IRSD. The results suggest that increased IgG4+ cells may rarely be seen in non-IRSD lymph nodes.

The value of immunohistochemistry for CD14, CD123, CD33, myeloperoxidase and CD68R in the diagnosis of acute and chronic myelomonocytic leukaemias

Rollins‐Raval M A & Roth C G 
(2012) Histopathology 60, 933–942

TIM3 expression by leukemic and non-leukemic myeloblasts†

T‐cell immunoglobulin mucin‐3 (TIM3) has recently been described as an acute myeloid leukemia (AML) stem cell antigen expressed on leukemic myeloblasts, but not on normal hematopoietic stem cells. TIM3 is also expressed by monocytes, natural killer cells, and several T cell subsets; however, normal myeloblasts have not been well‐characterized or compared to AML. A specific flow cytometric marker capable of separating leukemic myeloblasts from non‐neoplastic myeloblasts would be diagnostically useful, especially in the post‐chemotherapy setting.

De novo acute myeloid leukemia with Philadelphia chromosome (BCR-ABL) and inversion 16 (CBFB-MYH11): report of two cases and review of the literature.

Cytogenetic and molecular studies play a major role in myeloid disease subclassification and risk stratification. The 2008 World Health Organization (WHO) classification [1] recognizes several diseasedefining recurrent genetic abnormalities in acute myeloid leukemia (AML), one of which is inversion 16(p13q22) or t(16;16), which fuses the CBFB gene to the MYH11 gene, and is characteristically associated with myelomonocytic differentiation, abnormal eosinophils, and a good prognosis [2]. The hallmark of chronic myelogenous leukemia (CML) is the Philadelphia chromosome (Ph), formed as a result of the BCR–ABL translocation; however, the BCR–ABL abnormality is not specific to CML and may also be seen in precursor lymphoid neoplasms and rare cases of de novo AML [3,4]. Coexistence of Ph(BCR–ABL1) and inv(16)(CBFB–MYH11) is extremely uncommon, with only 30 cases reported in the literature. The majority of these cases represent the blast phase of CML (CML-BP), and have shown an aggressive clinical course with rapidly progressive disease and resistance to chemotherapy [5,6]. In contrast, the few reports regarding de novo Phþ inv(16)þ AML have suggested a more favorable prognosis [6–14]. We report the clinicopathologic features of two new cases of de novo AML with the Philadelphia chromosome and inversion 16 and review the literature. Case one is a 30-year-old female who presented with leukocytosis (white blood cell count [WBC] 47.96 10/L) with circulating blasts (7%), monocytosis (54%), and thrombocytopenia (1146 10/L). The bone marrow was nearly 100% cellular and normal marrow elements were replaced by a prominent myelomonocytic infiltrate, with manual differential counts showing increased blasts (9%), monocytic cells (28%), and eosinophils (18%) with abnormal, basophilic granulation. Flow cytometric analysis confirmed increased CD14þ monocytic cells and an aberrant myeloblast population, which was CD347CD117þCD33þ. Classical cytogenetic studies showed the following complex karyotype: 46,XX, t(9;22;17;19)(q34; q11.2; q25; p13.1), inv(16) (p13q22)[19]. Quantitative real-time (RT)-polymerase chain reaction (PCR) studies performed on the peripheral blood and bone marrow confirmed the presence of a BCR–ABL fusion transcript at the minor breakpoint cluster region (p190). Therapy included hydroxyurea, allopurinol, imatinib (600 mg/day), and high dose chemotherapy with busulfan and cyclophosphamide, followed by an allogeneic stem cell transplant. Although a complete clinical, cytogenetic, and molecular remission was initially attained, the patient relapsed 29, 53, 70, and 80 months after the initial diagnosis. The first three relapses were responsive to cytarabine-based

The number and growth pattern of plasmacytoid dendritic cells vary in different types of reactive lymph nodes: an immunohistochemical study

Plasmacytoid dendritic cells, which play a fundamental role in the innate immune response, are best known for their presence in hyaline-vascular Castleman disease and histiocytic necrotizing lymphadenitis. The relative number and distribution in many reactive entities as detected using more sensitive methods are uncertain, and their diagnostic implications are unknown. Immunohistochemical studies for plasmacytoid dendritic cell-associated markers CD123 and CD2AP were performed on 42 lymph nodes with hyaline-vascular Castleman disease, histiocytic necrotizing lymphadenitis, sarcoidosis, necrotizing granulomatous inflammation, viral infection, dermatopathic lymphadenopathy, autoimmune disease, and a histologic pattern compatible with toxoplasmosis. The overall plasmacytoid dendritic cell numbers and growth patterns (tight aggregates, loose aggregates/clusters, scattered single cells) were assessed. Plasmacytoid dendritic cells were present in all cases and were predominantly distributed in loose aggregates/clusters or singly. They were most numerous in granulomatous inflammation and histiocytic necrotizing lymphadenitis, whereas viral infections showed the fewest overall numbers and a predominant pattern of scattered single cells. Tight aggregates of plasmacytoid dendritic cells were most numerous in hyaline-vascular Castleman disease (100% sensitive, 68% specific). Plasmacytoid dendritic cells are not limited to a small number of reactive lymphadenopathies but are found in many reactive processes, often with a predominant pattern of loose aggregates/clusters and scattered single cells. However, tight aggregates were a characteristic feature of hyaline-vascular Castleman disease, and viral infections typically showed only few scattered cells distributed singly.

The Virtual Pathology Instructor: a medical student teaching tool developed using patient simulator software ☆ ☆☆

Virtual microscopy has been adopted by many medical schools but often without addressing the need for students to understand how to integrate slide observations with other diagnostic information. The goal of this study was to develop an innovative tool for teaching pathology to medical students that presents a variety of virtual materials necessary for a complete pathology evaluation. The Virtual Pathology Instructor (V-PIN) is patient simulation software (vpSim) created and supported by the University of Pittsburgh School of Medicine, Laboratory for Educational Technology, and allows students to assume the role of a diagnostic pathologist. V-PIN utility was demonstrated by educationally significant improvement between pretest and posttest scores for 2 cases (mean, 3.8 versus 4.2; P = .0007; 1.9 versus 3.0; P = .0001). A third case did not perform as well (mean, 2.5 versus 2.3; P = .12) but detailed evaluation of the performance of the case identified possible improvements. Maximum posttest performance was seen following both the traditional workshop and the V-PIN case as compared to the case alone (posttest 4.2 versus 3.0; P < .0001). No significant difference was identified in student progress through V-PIN cases taken before or after the related traditional workshop, as demonstrated by total time on task, number of steps to complete, total score, number of incorrect answers, and number of requests for V-PIN help. Patient simulation software is an effective tool for teaching pathology to medical students and can provide individual instruction and immediate feedback as well as identify opportunities to refine and enhance the educational experience.

ALDH, CA I, and CD2AP: novel, diagnostically useful immunohistochemical markers to identify erythroid precursors in bone marrow biopsy specimens.

Neoplastic erythroid proliferations may represent a diagnostic challenge owing to the difficulty in characterizing immature erythroblasts. Immunohistochemical expression of aldehyde dehydrogenase (ALDH), carbonic anhydrase isoenzyme I (CA I), and CD2-associated protein (CD2AP) was assessed in 66 bone marrow biopsy specimens and compared with glycophorin A and E-cadherin. ALDH, CA I, and CD2AP labeled neoplastic erythroblasts in most acute erythroid leukemias (AELs) and myelodysplasias and highlighted benign erythroid precursors within normal marrows, erythroid hyperplasias, acute lymphoblastic leukemias (ALLs), blastic plasmacytoid dendritic cell neoplasm, and most acute myeloid leukemias (AMLs). In 2 AELs, CD2AP was negative, and 1 AML lacked identifiable ALDH+ erythroid precursors. Immature erythroblasts were strongly ALDH+, weakly CA I+, weakly CD2AP±, E-cadherin±, and weakly glycophorin A±. AML was uncommonly weakly positive for ALDH, CA I, and CD2AP, and lymphoblasts from 1 ALL were weakly ALDH+. ALDH, CA I, and CD2AP are sensitive and relatively specific immunohistochemical markers for the erythroid lineage. ALDH is superior to glycophorin A and E-cadherin in highlighting immature erythroblasts.

Biclonal IgD and IgM Plasma Cell Myeloma: A Report of Two Cases and a Literature Review

Biclonal plasma cell myelomas producing two different isotypes of immunoglobulins are extremely rare entities; to date, the combination of IgD and IgM secretion by a biclonal plasma cell myeloma has not been reported. Bone marrow biopsy immunohistochemical studies in two cases revealed neoplastic plasma cells coexpressing IgD and IgM, but serum protein electrophoresis identified only the IgM monoclonal paraprotein in both cases. Biclonal plasma cell myelomas, while currently not well characterized in terms of their clinical behavior, should be distinguished from B-cell lymphoma with plasmacytic differentiation, given the different therapeutic implications. Both cases reported herein demonstrated chemotherapy-resistant clinical courses.