April 1997

Case-of-the-Month

 

Electron Microscopy

The ultrastructural findings were most interesting. Some of the noncohesive neoplastic cells showed variably sized, structures that often occupied a considerable portion of the cytoplasm and that were responsible for the signet-ring appearance on light microscopy (Fig. 5). In some cases, these intracytoplasmic spaces appeared to represent a complex spatial organization of the cell surface and cytoplasmic cell processes (Figs. 5 and 6), while in other cells the enlarged spaces seemed to be devoid of surface specializations and contents (Fig. 5). Typical microvilli, of the type usually associated with adenocarcinomas, were not identified either on the cell surface or within the intracytoplasmic lumens (Figs. 5 and 6). Instead, a few thin, elongated and often slightly curved filopodial processes projected from the surface of intracytoplasmic lumens, as well as focally from the surface of the tumor cells (Figs. 5 through 8). Neither glycocalyx nor glycocalyceal bodies were present (Figs. 7 and 8). Mucin granules were not present within the cytoplasm and the lumens did not contain any typical secretory products (Fig.  8). A prominent cytoskeleton of intermediate filaments and thin wisps of tonofibrils were present in all cells. There was loss of cell cohesiveness with marked reduction in the number of cell junctions. The cell nuclei showed segregated nucleoli and evenly distributed chromatin granules. Centrioles were easily identified.

   
Figure 5. Tumor cells, many of which are not closely associated or joined by junctions, with single and
multiple intracytoplasmic lumens. 		Figure 6. Higher magnification of multiple intracytoplasmic lumens. Some of the lumens have sparse cellular projections from the membranous surface.
   
Figure 7. With the nucleus at one edge of the tumor cell, the associated intracytoplasmic lumen has a few filopodia-like projections of variable length and contour. Figure 8. Note the absence of glycocalyx, glycocalyceal bodies, secretory product and microfilamentous core rootlets.

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