Overexpression of Arginase 1 is linked to DNMT3A and TET2 mutations in lower-grade myelodysplastic syndromes and chronic myelomonocytic leukemia

Immune dysregulation is a common feature of myelodysplastic syndromes (MDS) and chronic myelomonocytic leukemia (CMML), particularly in early stages. However, the genetic basis remains poorly understood. We recently reported that macrophages from mice deficient in tet methylcytosine dioxygenase 2 (Tet2), a model of MDS/CMML, are hyperinflammatory and have increased expression of arginase 1 (Arg1). In macrophages and myeloid derived suppressor cells (MDSCs) expression of Arg1 contributes to T-cell suppression and immune evasion by L-arginine depletion, in the setting of chronic inflammation and cancer. Since human MDS and CMML are driven by TET2 mutations and associated with chronic inflammation, we hypothesized that arginase enzymatic activity and ARG1 expression would be increased in human MDS/CMML bone marrow. Elevated arginase activity was observed in bone marrow mononuclear cells of MDS and CMML patients with lower-grade features. Immunohistochemical studies confirmed that myelomonocytic cells overexpress ARG1. Additionally, mutations in the epigenetic regulators TET2 and DNMT3A corresponded to high ARG1 expression and activity. These findings suggest ARG1 is a biomarker of immune dysregulation in early MDS and CMML. Recent murine findings have implicated Tet2 and Dnmt3a in regulation of innate immunity. Our study suggests similar changes may be driven by human TET2 and DNMT3A mutations.

Silver in situ hybridization compared with immunohistochemistry in assessing HER2/neu status in fine-needle aspiration cytology

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Background: Fine needle aspiration (FNA) cytology is a common diagnostic tool in breast cancer used to establish diagnoses of primary, metastatic or recurrent lesions. In these settings, knowledge of the HER2/neu status is vital for optimal therapeutic decision. We examined the accuracy of HER2/neu testing in alcohol-fixed malignant aspirates.

Methods: FNAs with known HER2/neu status on concurrent/subsequent surgical specimen were retrospectively identified to select a study group of malignant aspirates in cell blocks (CB) from 38 breast and 18 axillary lymph nodes. This group was enriched for HER2/neu positive cases. Sequential sections were studied by IHC using rabbit monoclonal antibody 4B5 and SISH INFORM HER2 DNA and Chromosome 17 (both by Ventana Medical Systems, Tucson AZ, USA). IHC and SISH were evaluated by two pathologists according to 2007 ASCO/CAP criteria and results were compared with HER2/neu status of paired concurrent/subsequent surgical specimen.

Results: HER2/neu IHC on CB yielded 17/56 (30.6%) positive, 30/56 (53.6%) negative and 9/56 (16.1%) equivocal cases. HER2/neu SISH on CB revealed 25/56 (44.6%) amplified, 30/56 (53.6%) not amplified cases. In one case the test was uninterpretable. HER2/neu status on available on 54 surgical specimens (combined IHC and ISH results) was positive in 26 cases and negative in 28. The concordance between negative or positive IHC and SISH on cell blocks was 93.6%. SISH on cell blocks could predict the HER2/neu status in 98.2% of surgical specimens whereas after exclusion of equivocal results, IHC on cell clocks could predict it in only 91.1%. Of the 26 cases with positive HER2/neu status, IHC-CB revealed 3 cases that scored 1+ and one case that scored 0 on cell block. These cases would have been misclassified if HER2/neu was tested on CB by IHC alone.

Conclusions: SISH is a reliable methodology for testing HER2/neu in alcohol fixed cytology specimens and is superior to IHC in its ability to accurately predict the final HER2/neu status. Alternatively, cases can be first tested with IHC and further tested with in situ hybridization when the score is under 3+ to avoid false negative results.

Endocervical reactive atypia: a histologic-cytologic study

Of 1,500 cervical tissue specimens, 27 cases showed histologic changes of reactive glandular atypia which we defined as endocervical cells with large hyperchromatic, often irregular nuclei, which did not fulfill the criteria for endocervical adenocarcinoma. Eighteen of these 27 cases had preceding or concurrent cervico-vaginal smears. Six of these showed cells which were similar to those seen in histologic sections. The cytologic characteristics of these cells are defined. To determine if atypia is related to inflammatory-regenerative changes, 29 cases of endocervical polyps were examined, of which 11 showed histologic changes of endocervical reactive atypia; 4 showed these changes cytologically as well. Twenty-eight cases of routine hysterectomy specimens were examined, of which 2 cases showed endocervical reactive atypia, which indicated that the atypical changes were indeed reactive. Nine out of 27 cases were associated with hormonal usage. Fourteen cases were associated with squamous intraepithelial lesions or evidence of human papilloma virus. Follow-up of our 27 index cases revealed no progression to adenocarcinoma. These findings indicate that atypia, as we define it, of the endocervix can be due to inflammatory-reparative changes or possibly related to hormonal usage, and permit its separation from precursor lesions of endocervical adenocarcinoma.