Chloroma - acute myeloid leukaemia

Case contributed by Frank Gaillard
Diagnosis certain

3 weeks & 7 wk post Rx

ct

Three different CT studies with the axial images at the same level, obtained from the diagnosis (first) to 7 weeks after chemotherapy (third imaged).

There are two solid vividly enhancing left frontal lobe masses leading to prominent mass effect with vasogenic oedema. The lesions have significantly improved over time. 

MRI Brain

mri

The two left frontal and the right cerebellar mass lesions have all similar imaging characteristics, they are vividly enhancing masses with diffusion restriction and local masse effect. 

Case Discussion

Diagnosis: Peripheral blood, bone marrow aspirate and biopsy: WHO classification - Acute myeloid leukaemia with inversion of chromosome 16.

Left frontal mass, biopsies: Acute myeloid leukaemic infiltrates in cerebral white matter consistent with granulocytic sarcoma (Chloroma).

 

Microscopy: Sections A1-A4 show small fragments of gray and white matter. In sections A1, A3, and A4, the white matter is partly invaded by a dense malignant cell infiltrate composed of immature granulocytic cells displaying round cells with hyperchromatic nuclei and high nuclear:cytoplasmic ratio. Some tumour cells have more abundant cytoplasm filled with eosinophilic granules. The leukaemic cells are distributed around blood vessels and are also diffusely infiltrating the white matter. In addition, tumour cells are seen within the lumen of cerebral microvessels. In section A1, small foci of early tumour necrosis are seen. Apoptotic nuclei are frequent. By immunohistochemistry, the leukaemic cells show strong membrane staining for leucocyte common antigen (CD45) and strong cytoplasmic staining for myeloperoxidase and CD43, consistent with the diagnosis of granulocytic sarcoma (chloroma). Rare reactive CD3-positive T-lymphocytes are present. The neoplastic cells are negative for CD20. Reactive astrocytes are seen in sections A1, A3, and A4 in association with the malignant cell infltrates, as well as in the adjacent white matter.

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