Parotid gland cancer.

<p>(<b>A</b>) CCEM shows proteasome immunofluorescence (green) distributed inside cytoplasmic PaCSs while sparing the nucleus (<b>A</b>, 3,000x). The boxed area is enlarged in <b>B</b> (50,000x) to magnify parallel 20S immunogold reactivity despite loss of density of barrel-like particles. Note in <b>A</b> mitochondria and clear unreactive areas merging with PaCS areas. In <b>C</b> (3,000x) a ballooning tumour cell with remnant of a central picnotic nucleus (arrow) is almost entirely formed by a degenerating PaCS only partly reactive to proteasome fluorescence. The boxed area, taken in <b>C</b> at the transition border between its highly and poorly fluorescent parts, shows in <b>D</b> (50,000x) the disappearance of particles and 20S proteasome immunogold below the border, in parallel with immunofluorescence. Another boxed area taken from the top of the heavily fluorescent part in <i>C</i>, shows well-preserved particles and proteasome immunogold in <b>E</b> (50,000x). (<b>F</b> and <b>G</b>) TEM (5,000x) showing two neoplastic cells, one with well-preserved normal nucleus (left), the other (right) with intranuclear accumulation of PaCS-like particles and proteasome immunogold, part of which is boxed in <b>F</b> and enlarged in <b>G</b> (50,000x). Note in <b>F</b> abundant mitochondria. n, nucleolus. (<b>H</b>) Bulging neoplastic cell with a small nucleus surrounded by a rim of dense cytoplasm and immersed in a lake of PaCS-type partly proteasome-reactive, particulate material (4,000x); the boxed area is enlarged in <b>I</b> (20,000x) with islets of residual cytoplasm, one of which is further enlarged in <b>L</b> (75,000x) to show a qualitative autophagic vesicle with double membrane enclosing a collection of well-preserved immunoproteasome-reactive PaCS-type particles. Note in <b>H</b> and <b>I</b> (arrowheads) three other double membrane delimited bodies enclosing PaCS-type particles.