Blood, Vol. 92 No. 12 (December 15), 1998:
pp. 4863-4863
PHOTOGRAPH
View larger version (116K):
[in this window]
[in a new window]
|
Megahemopseudophagocytosis. A 78-year-old man with myelodysplasia
(MDS) of the refractory anemia (RA) subtype evolved to chronic
myelomonocytic leukemia (CMML) over several years. Unexpectedly, his
bone marrow demonstrated 17% plasma cells and further evaluation was
consistent with an underlying plasma cell dyscrasia (PCD). It is
noteworthy that his bone marrow also showed a marked increase in
megakaryocytes (A through D) and megakaryocytic fragments (E and F),
many of which (48%) displayed engulfment of erythroblasts (A through
C), PMNs (A, B, and F), and/or lymphocytes (A and C through E),
up to 10 per cell. "Phagocytosis" of blood elements (red blood
cells, crythroblasts, lymphocytes, and myeloid cells) by megakaryocytes
has only been discussed sporadically in the literature and was termed
emperipolesis (wandering of one cell into another) in 1956 (Humbel et
al, Br J Haematol 2:283, 1956). Because neither cell is
damaged, this phenomenon does not represent true phagocytosis. It has
been described in leukemias, MDS, myeloproliferative disorders,
reactive thrombocytosis, malignancies, HIV, and ITP (Rozman et al,
Br J Haematol 48:510, 1981). The mechanism and significance is
unclear, and various theories concerning cytokines, adhesion molecules,
increased cell traffic across the marrow-blood barrier, megakaryocytic
cytoplasmic protection against a hostile bone marrow environment, and
response to injured or altered megakaryocytes has been postulated (de
Pasquale et al, Br J Haematol 60:384, 1985). Our case
exemplifies this unusual phenomenon and is possibly attributed to his
MDS/and or PCD. Our patient's megakaryocytes appear to be more
extensively involved than what has been previously described in the
literature (48% v 30%) and include the internalization of all
cell types, which also seems to be somewhat atypical. A more
descriptive and memorable term for this entity might be
megahemopseudophagocytosis. (Courtesy of Nancy J. Freeman, MD, and
Angelina C. Carvalho, MD, Brown University School of Medicine, Oncology
Section, Department of Veterans Affairs Medical Center, 830 Chalkstone
Ave, Providence, RI 02908-4799.)
|
|
