Metastasis of a histologically benign--appearing meningioma to the iliac bone.

PMGCT stroma and vessels within the yolk sac tumor component of these tumors. It can be further speculated that expression of hematopoietic growth and differentiation factors in some PMGCT could drive the differentiation of primordial germ cells into hematopoietic progeny. The differentiation factors involved may be responsible for the preferred commitment of the transformed precursors to megakaryocytic and monocytic lineage. Additionally, in a few cases of PMGCT-associated leukemia in which the immunophenotype of the leukemic cells was compared with that of the intratumoral hematopoietic precursors, a comparable result was observed. This suggests a spread of hematopoietic tumor cells from the PMGCT to blood, bone marrow, and/or extramedullary sites. The median time for the development of hematologic neoplasia associated with PMGCT is 6 months (range, 0 to 47 months). The clinical course of the hematologic neoplasia is very aggressive with a median survival of 5 months (range, 0 to 16 months) after diagnosis. Hematologic malignancies occurring in patients with PMGCT are thought to be primary, and not therapy related. In some cases, immunohistochemical and cytogenetic evidence (especially presence of i12p chromosome) had previously suggested the clonal relationship between the PMGCT and the hematologic malignancy. As in other previously reported cases, the short interval between the PMGCT and the occurrence of the hematopoietic malignancy argues against a therapy-related origin of the acute megakaryocytic leukemia. There have been two reported cases of PMGCT complicated by acute megakaryotic leukemia, one presenting with an extradural mass and the other with organomegaly. However, our patient is the first, to our knowledge, to be ever reported in English literature of a PMGCT evolving into an extramedullary acute megakaryocytic leukemia manifesting as a mass causing cord compression. Furthermore, the aggressive course of the acute megakaryoblastic leukemia involving the CNS with sparing of the bone marrow is striking.