Revisiting Howell-Jolly Body-Like Cytoplasmic Inclusions in Neutrophils: A Report of Two Cases and Confirmation of Nuclear Origin.

Howell-Jolly body-like inclusions in neutrophils have been reported in a handful of reports; however, their nuclear origin has never been confirmed to date. We report the presence of these cytoplasmic inclusions in two cases and confirm their DNA-based origin by fluorescent nuclear staining. Peripheral blood smears were manually reviewed by light microscopy and after 4',6-diamidino-2-phenylindole (DAPI) fluorescent staining via confocal microscopy. Methanol fixed peripheral blood smears were incubated with DAPI (Sigma Aldrich, St. Loius, MO, USA) and coverslipped with mounting media. DAPI-stained cells were imaged with a Leica SPE confocal microscope using a 405 nm excitation laser and a 63×/1.3 NA oil immersion objective. Optical sections spanning the entire cell thickness were acquired and maximum intensity projections were produced in ImageJ. Both cases described herein had Howell-Jolly body-like inclusions similar to those reported in the literature. Testing for relevant infectious etiologies was negative. Positive staining on fluorescence microscopy confirmed DNA-based origin of this cytoplasmic inclusion material. These DNA-based inclusions occur in the immunosuppressed patient and mimic infectious inclusions. While morphologically worrisome, recognition of these inclusions may prevent unnecessary treatment and testing in clinically appropriate patients.

Chronic myelomonocytic leukemia monocytes uniformly display a population of monocytes with CD11c underexpression.

OBJECTIVES: To examine the utility of CD11c expression on monocytes in normal controls and patients with chronic myelomonocytic leukemia (CMML) (n = 23) with flow cytometric immunophenotyping. METHODS: Twenty-three CMML samples and 10 control bone marrows submitted for lymphoma staging without evidence of disease were examined. RESULTS: Monocytes in CMML samples ranged from 4% to 35%. Expression of at least one aberrant monocytic marker was found on the monocytes in 18 (82%) of 22 evaluable cases. The most common aberrancy was underexpression of CD11c (n = 15), while none of the bone marrow controls showed underexpression of CD11c. CONCLUSIONS: A distinct heterogeneous population of monocytic cells with underexpression of CD11c was identified in all these cases. CD11c underexpression was independent of other aberrancies, including HLA-DR underexpression (n = 14), aberrant CD56 expression (n = 11), and underexpression of CD33, CD38, and CD14 (n = 6, 5, and 5, respectively), supporting the utility of CD11c expression status on monocytes in establishing a CMML diagnosis.