A serial section study of nuclear pockets and loops.

A serial section study of nuclear pockets in a lymphoma of the stomach showed that: 1) no tumour cell nucleus was free of pockets; 2) approximately 10 to 50 pockets occur on a nucleus; and 3) the pockets show a focal rather than a diffuse distribution on the nucleus. In most pockets cytoplasmic material is completely sequestrated and no channel of communication remains between the cytoplasm and the contents of the pocket. While most pockets contain cytoplasmic material, a few contain nuclear material. It would appear that these are two distinct and different lesions and that one does not evolve from the other. A serial section study of the so-called 'chromatin loops' shows that they are no more than fortuitous sections through pockets. The idea that 'chromatin loops' are cast off from the nucleus receives no support from our studies.