The apical portions of the Type II pnuemocyte have stubby microvilli that are also focally present on the lateral and basal aspect of the cell. Uranyl acetate lead citrate. A thin external lamina separates the neoplastic Type II pneumocytes from mesnchymal cells and collagen within the septa. These mesenchymal cells have convoluted nuclei, abundant rough endoplasmic reticulum, scattered intermediate filaments and focal plasmalemmal densities. Pools of glycogen displace the intracellular organelles.
Intermediate junctions are present between the processes of the mesenchymal cells.
Uranyl acetate lead citrate. Some nuclei of the neoplastic Type II pneumocytes contain intranuclear microtubules. Two types of surfactant granules are identified, one being the lamellar myelin figure and the other and electron dense granule.