Sections show a multi-loculated cystic lesion composed of dilated, interconnecting, thin-walled vascular channels proliferating within a mature fibrofatty stroma. These spaces are lined by a single layer of attenuated endothelial cells and contain pale eosinophilic proteinaceous fluid mixed with erythrocytes. The intervening fibrous walls host prominent lymphoid aggregates. Stromal areas reveal a bland proliferation of uniform spindle cells in loose collagenous sheets; significant nuclear atypia, necrosis, or mitotic activity are entirely absent.
Huge cyst covering the entire abdominal cavity with a very delicate surface, attached to the spleen, mesocolon, and up to the posterior surface of the stomach.
Received opened cyst wall measured 6x4 cm, totally embedded.
Abdominal cyst, excision: