Fig. 4

Representative histological features of the ia2 MPNSTs.

(A) In normal controls (i.e. non-neoplastic cases), transverse sections of the abdominal cavity show the gastrointestinal tract (center), surrounded by pancreatic and adipose tissue. The liver (top center and lower left) occupies more peripheral regions. (B-E) Abdominal MPNST. (B) The tumor occupies the abdominal cavity under the swim bladder and infiltrates the intestinal wall (arrowheads). (C, D) Cytologically, the lesion is composed of spindle to epithelioid cells with high nuclear-to-cytoplasm ratio, clumped chromatin and evident mitoses (arrowhead in D). (E) The intra-abdominal MPNSTs stains negative for AE1/AE3 (positive internal control: intestinal epithelial cells, stained in brown). (F) In non-neoplastic cases, transverse sections of the cranial region display the oral cavity/pharynx (bottom center), lying beneath the basicranial structures (middle center) and the brain stem (top center). (G-L) Intrathecal MPNST. (G) The intrathecal neoplastic mass (star) compresses and displaces the adjacent medulla oblongata (arrowheads), without clear-cut infiltration of the neural parenchyma. (H, I) Cytologically, the lesion closely resembles its intra-abdominal counterpart. (L) Pan-cytokeratin immunostain is also negative in intrathecal MPNST (star). Arrowheads: tumor/brain stem interface.