Recent studies have shown that papillary
renal cell carcinoma (RCC) is clinically and
genotypically a distinct entity. Papillary RCCs account
for about 10-15% of renal parenchymal neoplasms.
Macroscopically, the cut surface is yellow or brown in
color and large tumors frequently show cystic change.
Hemorrhage and necrosis are common. Histologically,
Delahunt and Eble have classified papillary RCCs into
type 1 (small cells, single layer) and type 2 (large cells,
pseudostratification) according to the cytoplasmic
volume and thickness of the lining cells. In
chromosomal analysis, gain of chromosomes 7 and 17,
loss of Y chromosome and additional gains
(chromosome 3q, 8p, 12q, 16q and 20q) are frequently
found in type 1 papillary RCCs, but the chromosomal
aberration of type 2 papillary RCCs seems to be more
heterogenous than that of type 1 papillary RCCs.
Mutations of MET proto-oncogenes in some cases of
both hereditary and sporadic papillary RCCs have
recently been detected. Furthermore, all hereditary and
sporadic papillary RCCs with MET proto-oncogene
show type 1 histological features. Type 1 papillary RCCs
generally seem to have a favorable prognosis, but type 2
tumors have a worse prognosis than do type 1 tumors.
Papillary RCCs with involvement of the X chromosome
and cancer syndrome with predisposition to
cutaneous/uterine leiomyomas and papillary RCCs, the
histological features of which are basically different
from those of usual papillary RCCs, have also been
recently reported. Since papillary RCCs seem to
constitute clinically, histologically, and even genetically
more heterogenous groups than previously thought,
further investigations are needed to characterize the
subtype of papillary RCC