Gastric Myeloid Metaplasia: A Case Report and Review of the Literature

Archives of Pathology & Laboratory Medicine,  May 2004  by Chatelain, Denis,  Devendeville, Agnès,  Rudelli, Alain,  Bruniau, Alexis,  Et al

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We report a case of gastric myeloid metaplasia in an 89-year-old woman with agnogenic myeloid metaplasia. The lesions were fortuitously discovered on upper endoscopy. The antral mucosa was thickened and polypoid, and on histologic examination contained immature granulocytes, megakaryocytes, and a few erythroblasts without desmoplastic stromal reaction. The granulocytes were positive for CD15, CD68, and myeloperoxidase on immunohistochemistry, and the megakaryocytes showed positive reactivity for factor VIII. Gastric myeloid metaplasia is a very rare event, and to our knowledge only 6 cases have been reported in the literature to date. It usually occurs in patients with advanced myeloproliferative syndrome. Gastric myeloid metaplasia often has a pseudotumoral appearance, leading to digestive symptoms. Histologic diagnosis is straightforward when trilinear hematopoietic elements are identified in gastric biopsies. Immunohistochemistry with anti-factor VIII antibody can be useful to confirm the presence of megakaryocytes.

(Arch Pathol Lab Med. 2004;128:568-570)

Myeloid metaplasia of the stomach is a very rare event.1-6 It usually occurs in patients with myeloproliferative disorder, and it is characterized histologically by the presence of trilinear hematopoietic elements in the gastric wall.1-6 We report a case of gastric myeloid metaplasia in an 89-year-old woman with myelofibrosis and myeloid metaplasia and review the literature on this topic.

REPORT OF A CASE

An 89-year-old woman with a past history of hip arthroplasty, chronic renal failure, atrial tachyarrhythmia, and amiodarone-induced hypothyroidism presented with asthenia. She had been diagnosed 2 years previously with agnogenic myeloid metaplasia and had been treated with hydroxyurea for several months. On physical examination, the patient had cutaneous pallor and a firm and markedly enlarged spleen. Laboratory findings included the following: hemoglobin, 8 g/dL; hematocrit, 26%; red blood cell count, 3.25 × 10^sup 6^/µL with dacryocytes and marked anisopoikilocytosis; leukocyte count, 32 × 10^sup 3^/µL with 5% myelocytes, 5% metamyelocytes, and 5% myeloblasts; and platelet count, 31 × 10^sup 3^/µL. The patient did not complain of digestive symptoms, but to rule out occult digestive bleeding, a gastroduodenal endoscopy was performed. It showed an unusual appearance of thickened and polypoid antral mucosa.

PATHOLOGIC FINDINGS

Microscopic examination of the gastric biopsies revealed the presence of cellular infiltrate in the mucosa and submucosa. This infiltrate was composed of numerous granular cells in all stages of differentiation, and a few atypical multinucleated megakaryocytes (Figures 1 and 2). Erythroid elements were rare. Blasts were not identified. No desmoplastic stromal reaction was evident. On immunohistochemistry, the granulocytes were positive for myeloperoxidase (Dako, Glostrup, Denmark; 1:150) (Figure 3) and CD15 antibodies (Immunotech, Marseille, France; 1: 50), and some were positive for CD68 (Dako, 1:100). Megakaryocytes were immunoreactive for factor VIII (Dako, 1:100) (Figure 4). No hematopoietic cell was positive for CD34 (Immunotech, prediluted).

COMMENT

Primary myelofibrosis with myeloid metaplasia, also called agnogenic myeloid metaplasia, is a rare chronic myeloproliferative disorder of adults and elderly people.7 It is caused by the clonal proliferation of a multipotent hematopoietic progenitor cell.7 It leads to an abnormal population of hematopoietic cells, notably clonal megakaryocytes that release fibrogenic cytokines in the bone marrow and colonize extramedullary sites.7 Patients manifest splenomegaly, bone marrow myelofibrosis, and immature myeloid and erythroid cells with marked poikilocytosis and anisocytosis in the peripheral blood.7

Extramedullary hematopoiesis in myelofibrosis with myeloid metaplasia was originally believed to arise from the reactivation of fetal hematopoietic elements, occurring in compensation for a progressively failing fibrotic bone marrow. Current evidence suggests that extramedullary hematopoiesis could result from filtration of circulating myeloid precursors.7 The altered marrow stroma could provide hematopoietic cells access to the circulation, from which they are filtered by the spleen and other organs.7 The most common sites of extramedullary hematopoiesis are the spleen, liver, and lymph nodes.2 Other organs, such as the kidney, adrenal glands, lung, thymus, breast, serosal surfaces (pleura, pericardium, peritoneum), ovary, central nervous system, epidural space, skin, pancreas, epididymis, and retroperitoneal fat, may also be involved.1,2,5 Development of extramedullary hematopoiesis in the gastrointestinal tract is extremely rare.1-9 It can involve the small intestine,8 large intestine,2 and the esophagus.9

Gastric myeloid metaplasia is a rare event, and to our knowledge, only 6 cases have been reported in the literature to date (Table).1-6 It always occurs in patients with a myeloproliferative disorder, such as chronic myeloid leukemia,3 polycythemia vera,5 essential thrombocythemia,4 and primary myelofibrosis with myeloid metaplasia (Table).1,2,6 Patients often complain of abdominal pain, vomiting, or digestive bleeding (Table). On endoscopy or gross examination, gastric extramedullary hematopoiesis resembles a polyp, a mass, or a thickened gastric wall, sometimes with giant gastric folds (Table). The lesions result from the sequestration, accumulation, and proliferation of circulating myeloid progenitors in the gastric wall. Histologic examination reveals the presence of immature myeloid cells in all stages of differentiation, erythroid nests, and atypical megakaryocytes. Endothelial markers, such as anti-factor VIII antibody, can be useful in identifying atypical multinucleated cells as megakaryocytes on immunohistochemistry.10 Myeloid metaplasia can sometimes be accompanied by an intense desmoplastic stromal reaction,5 and these lesions have been referred to as fibrous hematopoietic tumors,11 extramedullary myeloid tumors, or sclerosing extramedullary hematopoietic tumors.12 The diagnosis of gastric extramedullary hematopoiesis can be made using gastric biopsies, as in the present case,6 but also has been made using gastric specimens taken during postmortem examination in 5 of the 6 reported cases.1-5 Gastric extramedullary hematopoiesis is often accompanied by extramedullary hematopoiesis in other organs (Table).1-5