U. Schmidt et al., ULTRASTRUCTURAL EVIDENCE FOR DIVERGENT AND ALTERNATING DIFFERENTIATIONS IN SPINDLE-CELL SARCOMA XENOGRAFTS, Journal of submicroscopic cytology and pathology, 29(2), 1997, pp. 187-195
Seven spindle cell sarcomas, 5 poorly differentiated ones and 2 modera
tely well differentiated ones, were established on nude mice and long
term passaging was done. Sarcoma strains were analysed electron micros
copically in an attempt to get further insight in spindle cell sarcoma
differentiation pathways. Ultrastructurally, the tumours were classif
ied as malignant peripheral nerve sheath tumour (3/7), leiomyosarcoma
(2/7), rhabdomyosarcoma (1/7), and spindle cell sarcoma not otherwise
classifiable (1/7). Undifferentiated tumour cells including fibroblast
oid ones predominated in most xenografts, whereas cells harbouring cyt
oplasmic specificities tended to be few in number. Nevertheless, diver
gent differentiations exhibiting unusual double or triple patterns cou
ld be documented ultrastructurally in 12/30 xenografts with juxtaposed
myomatous as well as nerve sheath-like cells and, in addition, histio
cytoid (MFH-like) elements in 3 of the xenografts. Moreover, sarcoma s
trains alternated fine structural constellations in the course of pass
aging, whereby different phenotypes, myomatous, nerve sheath-like, uns
pecific, or mixed ones, succeeded one another. These findings pursue r
ecent immunohistochemical data on multidirectional sarcoma differentia
tion by means of electron microscopy. They, furthermore, fit well into
the concept of multipotential stem cells as progenitors in mesenchyma
l differentiation and suggest microenvironment to play a modifying rol
e in the expression of cell differentiation.