Agnogenic myeloid metaplasia presenting with omental implants
Radiological work-up consisted of flat and upright abdominal
radiographs, an abdominal ultrasound, as well as a computed
tomogram (CT) of the abdomen and pelvis.
Ultrasound revealed massive hepatosplenomegaly without focal
solid lesions, an incidental 4-cm hepatic cyst, and moderate volume
ascites (figure 1). Abdominal and pelvic CT scan showed, in
addition to significant hepatosplenomegaly, moderate volume ascites
and mesenteric engorgement, as well as peritoneal thickening and
multiple discrete omental implants (figures 2 and 3).
Considering the patient's postmenopausal status and older age,
and her ascites and peritoneal implants, the possibility of
metastatic ovarian carcinoma was high in the differential
diagnosis. The patient was referred for CT-directed biopsy of the
The pathology findings were as follows: fine-needle aspiration
biopsy (FNAB) of the omental infiltrate (Wright stain 400x/600x)
showed a significantly increased number of myeloid precursors
The terms "myeloid metaplasia" and "extramedullary
hematopoiesis" are used to describe a pathologic process of ectopic
hematopoietic activity that may occur in any organ system but that
primarily affects the liver and spleen.1 Myeloid
metaplasia is not always associated with myelofibrosis, and either
of these processes may occur in the absence of a clonal
The incidence of agnogenic myeloid metaplasia is between 0.5 and
1.5/100,000 population,4,5 with an increased prevalence
in Ashkenazi Jews. Median age at diagnosis is approximately 65
years with no sex predilection.6 An initial clue to the
diagnosis of myelofibrosis is myelophthisis of the blood,
characterized by the presence of leukoerythroblasts (immature
granulocytes and nucleated red blood cells).
Clinically, patients usually present with profound fatigue,
weight loss, night sweats, low-grade fever, and marked
splenomegaly, the latter related to extramedullary hematopoiesis.
Anemia is present and is usually multifactorially related to
ineffective erythropoiesis, erythroid hypoplasia, and
Agnogenic myeloid metaplasia can present with several
complications, including portal hypertension, associated with
ascites or variceal bleeding. This is seen in approximately 7% of
patients8 and may be related both to increased portal
flow due to marked splenomegaly and to intrahepatic obstruction due
to thrombotic obliteration of small portal veins.9
Splenic infarction may also occur, but episodes are usually
self-limited. Refractory cases may require splenectomy or splenic
Extramedullary hematopoiesis may occur at sites other than the
spleen, including lymph nodes and serosal surfaces, leading to
effusions and ascites in the lungs causing a pneumonia-like
process, etc. This phenomenon has also been reported in the
paraspinal and epidural spaces, leading to spinal cord and nerve
root compression. Extramedullary hematopoiesis not involving the
liver or spleen is usually managed with low-dose external beam
irradiation.10 A case of agnogenic myeloid metaplasia
with pericardial extramedullary hematopoiesis presenting as acute
cardiac tamponade has been reported. To our knowledge, a case of
agnogenic myeloid metaplasia presenting with omental implants has
not been reported in the radiology literature.
1. Ward HP, Block MH. The natural history of agnogenic myeloid
metaplasia and a critical evaluation of its relationship with the
myeloproliferative syndrome. Medicine.
2. Moran CA, Suster S, Fishback N, Koss MN. Extramedullary
hematopoiesis presenting as a posterior mediastinal mass: A study
of four cases. Mod Pathol. 1995;8:249-251.
3. McCarthy DM. Fibrosis of the bone marrow: Content and causes.
Br J Hematol. 1985;59;1-7.
4. McNally RJ, Rowland D, Roman E, Cartwright RA. Age and sex
distributions of hematologic malignancies in the UK. Hematol
5. Mesa RA, Silverstein MN. Population based incidence and
survival figures in essential thrombocytopenia and agnogenic
myeloid metaplasia. Am J Hematol. 1999; 61:1-5.
6. Kvasnicka HM, Thiele J, Werdec C. Prognostic factors in
idiopathic osteomyelofibrosis. Br J Hematol.
7. Thiele J, Windeckee R, Kvasnicka HM, et al. Erythropoiesis in
primary (idiopathic) osteomyelofibrosis: Quantification,
PCNA-reactivity, and prognostic impact. Am J Hematol.
8. Silverstein MN, Wollager EE, Baggenstoss AH. Gastrointestinal
and abdominal manifestations of agnogenic myeloid metaplasia.
Arch Internal Med. 1973;131:532-537.
9. Wanless IR, Peterson P, Das A, et al. Hepatic vascular
disease and portal hypertension in polycythemia vera and agnogenic
myeloid metaplasia: A clinicopathologic study of 145 patients
examined at autopsy. Hepatology. 1990;12:1166-174.
10. Bartlett RP, Greipp PR, Tefferi A, et al. Extramedullary
hematopoiesis manifesting as a symptomatic pleural effusion.
Mayo Clin Proc. 1995;70:1161-1164.
Prepared by Chandana Lall, MD, Department of
Radiology; Fleurette Abreo, MD, Department of Pathology; Cherie Ann
Nathan, MD, Department of Otolaryngology; and Girish Agrawal, MD,
Department of Radiology, Louisiana State University Health Sciences
Center and the Feist Weiller Cancer Center, Shreveport,