Soft tissue tumors are a very heterogeneous group of tumors in terms of
histogenesis, morphology, cytogenetics, molecular biology, clinical
manifestation, and prognosis. Their spectrum is fascinating for
morphologists and basic scientists alike. Yet precisely this variability
in the morphologic manifestation of soft tissue tumors, specifically
their histologic and cytologic patterns, presents great difficulties to
any effort to categorize them. Although many soft tissue tumors are
today defined not only by histology but also by immunohistochemical,
cytogenetic, and molecular biological findings, the histogenesis of many
soft tissue tumors, in particular malignant ones, continues to be
unknown. This is associated with the fact that the actual precursor
cells that lead to these tumors have frequently not yet been identified.
For this reason, the customary classification of malignant soft tissue
tumors is primarily not histogenetic, but actually according to the
dominant phenotype, however characteristic it is. Of course, an exact
morphologic examination of soft tissue tumors con- tinues to be an
essential prerequisite for making a diagnosis and determining a therapy.
The use of a wide range of additional modern examination techniques,
however, can make a substantial contribution toward more precisely
defining the biological behavior of a tumor, which without doubt can
have therapeutic implications.