[Light- and electron microscopical investigation on the pathogenesis of Kaposi's sarcoma (author's transl)]

Occurrence of tubuloreticular structures and intracisternal paracrystalline inclusions in endothelial cells of tissue from different epidemiological types of Kaposi's sarcoma

Biopsied tissue specimens from 40 cases of classic, atypical classic, endemic, and AIDS-associated Kaposi's sarcoma (KS) were investigated by electron microscopy. To search for ultrastructural differences between non-AIDS-associated KS and AIDS-associated KS, the occurrence of the following 2 ultrastructural abnormalities of the rough-surfaced endoplasmic reticulum in KS cells was evaluated semi-quantitatively: tubuloreticular structures (TRS) and intracisternal paracrystalline inclusions (IPI). These peculiar structures were found in 23 of the 40 KS cases. Two types of TRS could be distinguished: loose TRS (LTRS) and compact ones (CTRS). LTRS were observed in endothelial cells of tissue from all the different epidemiological types of KS. CTRS were confined to AIDS-associated KS. IPI were present in endothelial tumor cells of only 3 non-AIDS-associated KS cases. The study shows that in cells of KS tissue only CTRS, but not LTRS, are an ultrastructural marker for AIDS-associated KS.

Fine structure of a malignant hemangioendothelioma of the esophagus

The histology and electron-microscopy of a malignant hemangioendothelioma of the esophagus wall appearing in a 42 year old male is presented. By light microscopy the tumor is composed of vessels and capillary-like structures of an anastomosing nature covered by atypical endothelial cells. These cells infiltrate the interstitial spaces growing into the posterior mediastinal area. Electron microscopy confirms the endothelial nature of the neoplastic cells, showing characteristics of the cell type, as is the presence of Weibel-Palade bodies, filaments and active pinocytosis. Hemangioendothelioma should be differentiated from other vascular tumors (angiosarcoma) as are hemangiopericytoma or hemangioblastoma, being composed exclusively of malignantly transformed endothelial cells.

Ultrastructure of one Ewing's sarcoma of bone with endothelial character and a comparative review of the vessels in 27 cases of typical Ewing's sarcoma

An atypical variant of Ewing's sarcoma, located in the left hip of a nine-year-old girl, is discussed at optical, histochemical and electron microscopical level. The endothelial appearing cells seem to play a main role in its histogenesis. Tumoral cells of an undifferentiated blastemic nature show round nuclei and bright lucent cytoplasm, being organized in solid sheets or vascular-like profiles. Alkaline and acid phosphatases are very prominent in all tumoral cells, and some of them also show PAS positive material. Its ultrastructure demonstrates an active pinocytic capacity, cytoplasmic filaments and Weibel-Palade bodies. Simultaneously a review is performed on 27 cases of typical Ewing's sarcoma of bone in order to compare its vessels of a reactive nature with this tumor. A differential diagnosis with hemangioendothelioma primary to bone is established.