Background. Malignant rhabdoid tumor (MRT), originally described as a
rare renal sarcoma in childhood, has been known to express phenotypic
diversity. In this study, unique characteristics of the MRT cells were
investigated by using established cell lines. Methods. Immunocytochem
ical, ultrastructural, cytogenetic, and molecular (by polymerase chain
reaction, PCR) analyses were done for two MRT cell lines, one of rena
l and one of extrarenal origin, before and after differentiation-induc
tion with either 12-O-tetradecanoyl phorbol-13-acetate (TPA) or transr
etinoic acid (RA). Results. The proliferating cells in the original tu
mor tissues as well as in the established cell lines demonstrated neur
al, epithelial, and mesenchymal markers morphologically. Both cell lin
es had karyotypic abnormalities including chromosome 22q11.2. The cell
line from the extrarenal MRT, Tm87-16, demonstrated distinct morpholo
gic changes with neuroblastic differentiation and produced numerous ne
uritic processes after treatment with either TPA or RA. The cell line
from the renal MRT, STM91-01, suggested schwannian differentiation but
did not change morphologically after chemical induction. Both cell li
nes expressed c-myc, but did not express N-myc, MyoD1, tyrosine hydrox
ylase, or neural cell adhesion molecule (N-CAM). With PCR and immunocy
tochemical study, a high level of chromogranin expression was detected
by the cells of Tm87-16 only after TPA induced differentiation. Concl
usions. MRT cells demonstrated diverse phenotype of neuro-ecto-mesench
ymal differentiation. The results of this study suggest that MRT may b
e derived from a primitive pluripotential cell, such as neural crest o
r equivalent. MRT, therefore, might be categorized as one of the subse
ts of primitive neuroectodermal tumor.