Submitting Author: Xie, Ming, MD
Institution: William Beaumont Hospital, OUWB School of Medicine, Troy, MI 48085
Session: Extramedullary manifestations of myeloid neoplasms

A 37 year old female presents with small bowel obstruction in 2008. An

intraoperative pathology consultation was requested with touch-prep smear examination. A hematopoietic neoplasm was suspected and fresh tissue submitted for flow cytometry and routine histological studies. The lesion was completely excised. A diagnosis of extramedullary myeloid sarcoma (acute myeloid leukemia) was made. Patient was treated accordingly with no recurrent or residual disease. Two subsequent repeat bone marrow biopsies show no evidence of acute myeloid leukemia. Patient is free of disease with 5 year follow up.

The small bowel excision specimen is submitted fresh. A 10.5 x 8.0 x 5.0 cm tan-yellow smooth, firm, ill-defined mass is identified with small bowel obstruction. The tumor appears infiltrating the full thickness of the small bowel wall in a permeation pattern, not disrupting the existing structure. The tumor tissue is formalin fixed and embedded in paraffin.

Microscopic examination shows diffuse infiltration of discohesive large cells with vesicular chromatin and small nucleoli. Some cells have orange granular cytoplasm. Occasional eosinophils are present. The tumor cells infiltrate the full thickness of small bowel wall with distension of the submucosal, subserosal and intramuscular spaces, without disruption of the usual anatomic structures.

Flow cytometry evaluation reports a large population of myeloid blasts.

The blasts are positive for CD13, CD15, CD33, CD34, CD38, CD45, CD58, CD71, CD117 and HLA-DR.

The blasts are negative for other myeloid markers (CD11b, CD14, CD16,

CD41, CD64, and glycophorin), as well as T-cell, B-cell and NK cell markers (CD2, CD3, CD5, CD7, CD8, CD10, CD19, CD20, kappa, lambda and CD56).

CD4 expression is equivocal.

Bone marrow biopsies with normal cytogenetic results.

Not done

1. Clinical presentation with small bowel obstruction, unusual location for acute myeloid leukemia.

2. Younger patient age comparing with the usual bone marrow based acute myeloid leukemia

3. Unique gross and histology features: diffuse permeation infiltrating pattern involving the full thickness of small bowel, without significant disruption of the usual anatomic structures.

4. Isolated lesion without bone marrow involvement with 5 year follow up.

5. Surgical excision is the treatment of choice.

Small bowel obstruction with extramedullary myeloid sarcoma (acute myeloid leukemia), completely excised

Additional immunohistochemical stains performed by the consensus group:

MPO: Strongly positive

Myeloid sarcoma involving small intestine

Case 103