| Session: Extramedullary manifestation of neoplastic myeloid disorder |
| Case number: 042 |
Submitter(s): Lawrence Zukerberg.
Clinical history
Patient is an eleven month old girl who at the age of five months developed multiple 2-5 mm red-brown papules on the face, trunk and extremities. These lesions were asyptomatic and some appeared to regress spontaneously.
Details of gross/microscopic pathology:
Skin biopsy from the left trunk showed a mononuclear infiltrate involving the superficial and deep dermis. The infiltrate was periadnexal with epidermal sparing and composed of medium sized primitive appearing cells with pale cytoplasm and folded nuclei.
Bone marrow biopsy and aspirates (performed twice 2 days apart) at that time showed trilineage hematopoiesis with an abnormal population of large cells with moderate amount of blue cytoplasm and large folded irregular nuclei and blast like chromatin. Blasts and promonocytes ranged from 6-13 percent of the cells. Histochemical staining for non-specific esterase was positive in the blasts.
Immunophenotype (flow cytometry/immunohistochemistry):
Immunohistochemistry performed on the skin biopsy showed the atypical cells were positive for CD117, CD34, CD68 and lysozyme. They were negative for CD1a, tryptase and myeloperoxidase. The Ki67 proliferation fraction was high (~90%).
Flow cytometry performed on the bone marrow aspirate revealed an abnormal poulation of blasts expressing CD33 and CD34, partial expression of CD 117 and without expression of CD14 or myeloperoxidase. These accounted for 4 to 6 percent of the total cells.
Cytogenetics:
FISH evaluatioon of the skin biopsy for MLL rearrangement was performed with the MLL Dual Color, Break Apart Rearrangement Probe at 11q13 and rearrangement was found in 28 of 50 nuclei (normal up to 1 percent). No abnormality was noted in chromosome 8.
Both marrow aspirates (perfomed 2 days apart) showed no clonal cytogenetic abnormalities. FISH evaluation for MLL rearrangement was negative with no rearrangement observed in 100 nuclei on either marrow aspirate.
Molecular analysis:
Interesting feature(s) of submitted case:
It is puzzling that the MLL rearrangement was seen in the skin biopsies (initially and at recurrence) but never in the bone marrow biopsies (2 pre-treatment and 3 after treatment). Multiple hematopathologists reviewed the original bone marrow biopsies and all felt there was marrow involvement. However the lack of detectable translocation raises the possibility that the marrow blasts could be reactive and not leukemic blasts.
Proposed diagnosis:
Myeloid sarcoma with monocytic features and MLL rearrangment by FISH involving skin.
Atypical population of blasts with monocytic and monoblastic features involving the bone marrow, negative for MLL rearrangment, suspicious for early marrow involvement by acute myeloid leukemia.
Panel diagnosis:
agree with proposed diagnosis
Comments:
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