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35 Cards in this Set

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  • Back
Nephroblastoma is a ___ embryonal neoplasm derived from __
- malignant
- nephrogenic blastemal cells
- replicates histology of developing kidney and often shows divergent patterns of differentiation
Prevalence of Wilms tumor

Age at diagnosis
1/8-10,000

90% < 6yo
98% < 10yo
mean age 3-4yo
uncommon in adulthood
Most common renal tumor of chilhood is __
nephroblastoma
Wilms tumor presents with __
- palpable mass (felt by parent)
- abd pain (maybe acute abd due to traumatic rupture)
- hematuria
- HTN
Wilms tumors are treated following two protocols (most cases)
International Society of Pediatric Oncology (SIOP)
- advocate preop therapy followed by resection

Children's Oncology Group (COG)
- advocate primary resection followed by therapy determined by classification into "favorable" and "unfavorable" histology categories

NOTE: both show similar outcomes despite divergent philosophies
nephroblastoma (gross)
- most are solitary
- rounded, well-demarcated with a fibrous pseudocapsule
- may be cystic
- rarely occur in extrarenal locations
Wilms tumor metastases typically spread to __, __, and __; metastatic tumor to other sites like bone or brain should suggest __
resitricted pattern of metastasis
- regional lymph nodes
- lung
- liver

-- suggest alternate dx
Wilms tumor staging in general involves
- identification of renal capsule penetration
- renal sinus vessel involvement
- margin status
- region lymph node status
Bilateral Wilms tumors are classified as stage __, however__
Stage V

- But, the prognosis is based on the stage of the most advanced tumor and the presence or absence of anaplasia (each tumor is separately staged)
Wilms tumor blastemal cells
- small, closely-packed, mitotically active, round to oval cells with scant cytoplasm, small nucleoli
Patterns of blastemal cells in Wilms tumor
Diffuse pattern
- LACK cellular cohesion (contrast to other patterns)
- aggressive pattern of invasiveness (contrast to typical circumscribed, pushing invasion of most tumors)

Nodular or Serpentine pattern
- round or undulating, sharply defined cords and nests of blastemal cells in a loose fibromyxoid stroma
Epithelial component of Wilms tumor can consist of
- primitive rosette-like structures
- tubular or papillary elements (recapitulating normal nephrogenesis)

Heterologous epithelial elements!
- most commonly mucinous and squamous epithelium

NOTE: DDX metanephric adenoma vs. epithelial Wilms tumor
- in Wilms the tumor cells are mitotically active and much larger than those of metanephric adenoma; metanephric adenoma is seen mainly in adult females (avg age 41)
- IMPORTANT NOTE: some epithelial Wilms tumors in adults and children can have areas identical to metanephric adenoma, so extensive sampling is required
- Metanephric adenomas are often positive for WT-1 too!!
Stromal component of Wilms tumor
- smooth muscle
- fibroblastic

Heterologous stromal components
- skeletal muscle (most common)

- adipose
- cartilage
- bone
- ganglion cells
- neuroglial tissue
Post-chemotherapy changes in Wilms tumor
- necrosis
- xanthomatous histocytic foci
- hemosiderin deposits
- fibrosis
- maturation of blastema, epithelial, and stromal components (striated muscle is most frequent)
In Wilms tumor, anaplasia correlates with ___ rather than __
responsiveness to therapy rather than aggressiveness
In Wilms tumor, histologic diagnosis of anaplasia requires
- multipolar, polypoid mitotic figures
-- abn metaphase must be as larger or larger than a nml metaphase

- marked nuclear enlargement and hyperchromasia
-- at least 3 times the size of a non-anaplastic nucleus in another area of the specimen
Focal vs. Diffuse anaplasia
- anaplasia is more consistently associated with poor px when diffuse

Focal anaplasia:
- one or a few sharply localized regions of anaplasia within a primary tumor, confined to the kidney
- majority of tumor has NO nuclear atypia
- Anaplasia must NOT be within vascular spaces
- Anaplasia must be confined to renal parenchyma

Tumors not meeting these critieria are classified as diffuse anaplasia
Wilms tumor IHC
blastemal cells
- vimentin +
- +/- focal CK, desmin, NSE

WT-1
- not + in all Wilms tumors!
- correlates with histology
-- blastemal cells and areas of early epithelial differentiation are strongly WT-1+
-- stromal areas and areas of terminal epithelial differentiation are negative to weakly WT-1+
Pediatric renal maligancies include
- Nephroblastoma (80%)
- Nephroblastoma, anaplastic (5%)
- mesoblastic nephroma (5%)
- clear cell sarcoma
- Rhabdoid tumor
Misc:
- neuroblastoma
- PNET
- synovial sarcoma
- RCC
- angiomyolipoma
- lymphoma
- other
Syndromes with highest risk of nephroblastoma
- Denys-Drash syn (90% risk)
- WAGR syn (30%)
- Beckwith-Wiedemann syn
- hemihypertrophy
- familial nephroblastoma
patients with WAGR syn have ___ of WT1 gene, while patients with Denys-Drash syn have __
WAGR syn: deletions of WT1 gene

DD syn: point mutation in one copy of WT1 gene with tumors showing loss of other nml allele
Nephrogenic rests
abnormally persistent foci of embryonal cells capable of developing into nephroblastomas
Neophroblastomatosis
diffuse or multifocal nephrogenic rests
Nephrogenic rests are found in 25-40% of pts with __ and 1% of __
- nephroblastomas
- infant autopsies
nephrogenic rests can be divided into __ and __
PLNR (perilobar nephrogenic rests) and ILNR (intralobar NR)
PLNR can remain ___ or __
- dormant
- (most commonly) regress
- hyperplastic nephrogenic rest (almost impossible to distinguish from a nephroblastoma)
nephroblastoma developing in a PLNR is recognized by __
- spherical expansile growth with peritumoral fibrous pseudocapsule formation (similar for tumors arising in ILNR)
Diffuse hyperplastic nephroblastomatosis has a high risk of developing __
- nephroblastomas
- more likely to be multiple and exhibit anaplasia
cystic partially differentiated nephroblastoma is a __
- rare, multilocular cystic neoplasm of very young children
- composed of epithelial and stromal elements with nephroblastomatous tissue
cystic partially differentiated nephroblastoma is a Wilms tumor composed entirely of __
- cysts with delicate septa
- within septa are small foci of blastema, immature-appearing stromal cells, and primitive or immature epithelium
cystic partially differentiated nephroblastoma without nephroblastomatous elements is called __
- cystic nephroma, although this is NOT the same thing as teh morphologically similar cystic nephromas that occur in adults
cystic partially differentiated nephroblastoma occurs in __
- boys > girls
- most before 2yo
cystic partially differentiated nephroblastoma entirely made up of ___ and lack __
- cysts
- lack expansile nodules to alter the rounded cyst contour
Cysts in cystic partially differentiated nephroblastoma are lined by
- flattened, cuboidal, or hobnail epithelial cells
- may LACK an epithelial linig too
Septa in cystic partially differentiated nephroblastoma contain
- variably celullar differentiated and undifferentiated mesenchymal cells
- blastema
- nephroblastomatous epithelial elements
- skeletal muscle and myxoid mesenchyme are present in most tumors
- may see cartilage and fat