Metastatic malignant mixed tumor of the skin. Ultrastructural and immunocytochemical characterization, histogenetic considerations and comparison with benign mixed tumors of skin and salivary glands.

Malignant mixed tumors of the skin (chondroid syringoma) are exceedingly rare. Few reports can be found in the literature and there are only two published cases in which electron microscopy has been performed. The precise histogenesis of this neoplasm is still disputed and the nature and mechanism of secretion of the intercellular substance is unknown as yet. Some authors believe that in mixed tumors of salivary glands this material could be produced by myoepithelial cells. A case is reported in which ultrastructural and immunocytochemical studies were performed in an effort to elucidate the histogenesis of malignant mixed tumors of skin and their relationship to other benign mixed tumors of the skin and salivary glands. The new information that has been obtained is interpreted in light of the findings provided by all published reports of malignant mixed tumors of the skin.

Innervation of brain intraparenchymal vessels in subhuman primates: ultrastructural observations.

Sympathetic innervation of intraparenchymal blood vessels in the basal ganglia was demonstrated by transmission electron microscopy in arteries, arterioles, and capillaries of the subhuman primate brain. Small arteries (40-120 micron) and some arterioles (12-40 micron) are innervated only at branching sites. However, arterioles occasionally may be innervated at points distal to their origin. Capillary innervation was very infrequently observed.

Malignant small bowel neoplasm of enteric plexus derivation (plexosarcoma). Light and electron microscopic study confirming the origin of the neoplasm.

An unusual small intestinal tumor was found in a 61-year-old male who complained of intermittent right lower quadrant burning pain, tenesmus, and bloody diarrhea. On gross examination, the tumor was located intramurally in the distal jejunum with no involvement of the overlying mucosa. Histologic examination revealed two elements: a spindle cell component with characteristics reminiscent of a Schwann cell neoplasm, and nests of larger epithelioid-like cells almost undistinguishable from the Zellballen of nonchromaffin paragangliomas. The neoplasm originated within the intestinal wall without apparent mucosal origin. Ultrastructural studies revealed features recapitulating the normal enteric plexus structure and quite unlike those described in normal or neoplastic smooth muscle, Schwann or paraganglion cells. On this basis, this neoplasm is considered as a malignant enteric plexus tumor or a plexosarcoma.