Subcellular distribution of cytokeratin and vimentin in malignant rhabdoidtumor: Three-dimensional imaging with confocal laser scanning microscopy and double immunofluorescence

Malignant rhabdoid tumor (MRT) is a highly aggressive neoplasm that mostly occurs in childhood, characterized histologically by rhabdoid. cells as sho wn by eosinophilic intracytoplasmic inclusions. Although it is known that r habdoid cells co-express cytokeratin (CK) and vimentin, the distribution pa tterns of these two kinds of intermediate filaments and structural relation ship between them are still not known. We investigated the subcellular dist ribution of CKs 8 and 18 and vimentin in MRT cell lines (Tm87-16, STM91-01, TTC549, and TC289) using confocal laser scanning microscopy and double imm unofluorescence, in addition to ultrastructural examination. Vimentin was d iffusely expressed in the cytoplasm of MRT cells, focally forming a filamen tous network. In contrast, CKs 8 and 18 were partially expressed hi the cyt oplasm of MRT cells, forming globules or a few vague agglomerates. Three-di mensional images in TC289 cells revealed distinct distribution patterns of cytokeratin and vimentin, showing agglomerates of cytokeratins within the v imentin filament network. We conclude that these globules and agglomerates of CKs 8 and 18 correspond with the characteristic ultrastructural finding, showing cytoplasmic bundles of intermediate filaments concentrated in whor led arrays.