T. Ohno et al., SMOOTH TUBULAR AGGREGATES ASSOCIATED WITH PLASMALEMMAL INVAGINATION IN ALVEOLAR SOFT PART SARCOMA, Ultrastructural pathology, 18(3), 1994, pp. 383-388
The ultrastructure of four alveolar soft part sarcomas was examined to
search for ultrastructural signs of myogenic or neural origin. A new
ultrastructural structure, an unusual tubular structure, was found in
two of four cases. The structure appeared as a large, smooth, tubular
aggregate in the cytoplasm of some tumor cells but did not show a hone
ycomb arrangement of tubules. The aggregate was composed of long, serp
entine, branching, smooth, irregularly arranged tubules without riboso
mes that ran in various directions. The aggregates intermingled with s
mall amounts of cytoplasmic organelles. Because the aggregated tubules
were at times continuous with cell membranes, it was shown that they
were the complex extensions or invaginations of cell membranes. Neithe
r myelin-axon complexes nor myofilaments, including Z band material, w
ere seen in any case. There was a possibility that the smooth tubular
aggregate was a T-tubule-like structure, suggesting that the tumors we
re derived from skeletal muscle cells.