Eble JN, Sauter G., Epstein JI, Sesterhenn IA - iarc

Mixed epithelial and stromal tumour
J.N. Eble
Definition
Mixed epithelial and stromal tumour is a
complex renal neoplasm composed of a
mixture of stromal and epithelial elements.
Synonyms
Some authors have applied other names
(cystic hamartoma of renal pelvis or
adult mesoblastic nephroma) but the
name "mixed epithelial and stromal
tumour" best captures its nature {2035}.
Clinical features
There is a 6:1 predominance of women
over men {35}. All have been adults and
the mean age is perimenopausal (46
years). Presenting symptoms include
flank pain, haematuria or symptoms of
urinary tract infection; 25% are incidental
findings. Histories of estrogen therapy
are common. Surgery has been curative
in all cases.
to complex branching channels which
may be dilated. These varied elements
often are present intermingled in the
same area of the tumour. The stroma
consists of a variably cellular population
of spindle cells with plump nuclei and
abundant cytoplasm. Areas of myxoid
stroma and fascicles of smooth muscle
cells may be prominent. Densely collagenous
stroma is common and fat is
occasionally present. Mitotic figures and
atypical nuclei have not been reported.
Fig. 1.115 Mixed epithelial and stromal tumour.
Large tumour attached to the renal pelvis.
Macroscopy
The tumours often arise centrally in the
kidney and grow as expansile masses,
frequently herniating into the renal
pelvic cavity. The tumours are typically
composed of multiple cysts and solid
areas.
Histopathology
These are complex tumours composed
of large cysts, microcysts, and tubules.
The largest cysts are lined by columnar
and cuboidal epithelium, which sometimes
forms small papillary tufts.
Urothelium, which may be hyperplastic,
may also line some portion of the cysts.
The microcysts and tubules are lined by
flattened, cuboidal, or columnar cells.
Their cytoplasm ranges from clear to
pale, eosinophilic, or vacuolated.
Epithelium with müllerian characteristics
has also been described {205}. The
architecture of the microcysts is varied
and ranges from simple microcysts with
abundant stroma between them, to
densely packed clusters of microcysts,
A
Fig. 1.116 Mixed epithelial and stromal tumour. A Predominantly solid mass with scattered cysts. B Note
glancing inner surface of the cystic tumour.
Fig. 1.117 Mixed epithelial and stromal tumour forming spatulate papillae. Note fat cells in stroma.
B
Cystic nephroma / Mixedepithelial and stromal tumour
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