The operative specimen consisted of a sausage-shaped (3.5x2.0x1.2 cm), thinly-encapsulated mass of reddish-brown tissue (Fig 4). The cut surface has a mottled, vaguely nodular, homogeneous yellowish-brown appearance (Fig 5).
Microscopic examination of intra-operative smear (Fig 6), and paraffin sections (Fig 7 and Fig 8), shows the mass to be composed of sheets of hematopoeitic elements (Fig 9), including myeloid, red cell and megakaryocytic lines, the latter showing Factor 8-related Ag positivity (Fig 10). Special stains reveal an intense background angio-architecture of small, branching capillary-sized vessels (Fig 11).
MR scan signal attributes correlate with homogeneous cellularity (T1 isointensity) and abundant interstitial water separating the cells (T2 hyperintensity). Strong diffuse enhancement may be inferred from the numerous capillaries.