Institution: Memorial Medical Center, Springfield, Illinois
Session: Erythroleukemia and megakaryoblastic AML and mimics
HISTORY
36 year old gravida 6 para 3 at 38 weeks gestation presented with two day history of absent fetal movement. Uterine ultrasound revealed absent cardiac activity consistent with intrauterine fetal demise. After induction and delivery of the deceased fetus, an autopsy was declined. External examination of the fetus by the obstetrician revealed flattened nasal ridge, low set ears, nuchal skin thickening, and Simian creases. The placenta was sent for pathologic evaluation and chromosome analysis.
DETAILS
The 730 gram placenta was large for gestational age (>90th percentile for gestational age) and revealed no gross abnormalities. The tissue was fixed in 10% buffered formalin. Histologic sections revealed a monotonous population of large mononuclear cells within numerous chorionic vessels.
IMMUNOHISTOCHEMISTRY AND FLOW CYTOMETRY
Immunohistochemical stains showed that the large mononuclear cells were positive for CD45, CD43, CD117, CD34, CD33, CD15 (focal), and CD71 and were negative for CD3, CD20, myeloperoxidase, CD42b, and TdT. Flow cytometry and touch preparations could not be performed as the sample was already placed in formalin.
CYTOGENETIC FINDINGS
Karyotypic analysis was performed by ARUP Laboratories in Salt Lake City, Utah and revealed 47, XY+21 in all fourteen metaphase cells examined.
MOLECULAR FINDINGS
Molecular analysis was not performed.
INTERESTING FEATURES
Myeloid proliferations related to Down Syndrome (transient abnormal myelopoiesis versus acute myeloid leukemia) are most commonly diagnosed by morphologic and immunophenotypic evaluation of peripheral blood and bone marrow. This case illustrates that in the absence of these typical diagnostic modalities, this process can be identified by histologic and immunohistochemical evaluation of placental tissue.
PROPOSED DIAGNOSIS
Transient abnormal myelopoiesis of Down Syndrome versus acute myeloid leukemia associated with Down Syndrome
CONSENSUS DIAGNOSIS
Abnormal myelopoiesis associated with Down syndrome, with intrauterine fetal demise
| Low power evaluation (100X, H&E) reveals a population of mononuclear cells within chorionic vessels |  |
| Very high power evaluation (1000X, H&E) reveals a population of large mononuclear cells with fine chromatin and visible nucleoli within the chorionic vessels |  |
| Intermediate power evaluation reveals that the blasts express CD34 (200X) |  |
| High power evaluation shows that the blasts are positive for CD117 (600X) |  |
| Intermediate power evaluation reveals that the blasts express CD33 (200X) |  |
| Intermediate power evaluation reveals that the blasts are positive for CD71 (200X) |  |
| Intermediate power evaluation shows that the blasts are negative for myeloperoxidase |  |
| Intermediate power evaluation shows that the blasts are largely negative for CD42b |  |