Table 2 Main morphological, immunohistochemical (IHC) and molecular fidings among pediatric renal tumors

Wilms Tumor

Triphasic tumor: epitelial, stromal and blastema

WT1 (+)

CD57 (-)

WT1 mutation;

TP53 mut in anaplasic cases

Metanephric adenoma

Well defined borders, primitive epithelial cells, arranged in acini or tubules, without mitosis

PAX 8 (+)

CD57 (+)

BRAF (+)

WT1 (+)

BRAF mutation

Papillary renal cell carcinoma

Papillae áreas with histiocytes

CK7 (+) AMACR (+) WT1 (-)

MET alterations (trissomy of ch 7)

Clear Cell Sarcoma

Oval cells, with clear cytoplasm and nuclei with dispersed chromatin and imperceptible nucleoli; grouped in wide cords or nests, with the presence of vascularized septa (arboriform vessels)

BCOR(+) CCND1 (+)

BCOR mutation

MPNST

Spindle cells, with alternating hyper and hypocellular areas, with hemangiopericytic-like vascular pattern

H3K27me3 (-)

Histone methylation

Synovial sarcoma

Spindle cell are usually arranged in long fascicles, withing a stroma that ranges from collagenic to myxoid; can be biphasic, with presence of epithelial component

TLE1 (+) CD99 (+/-) WT1 (-)

t(X;18) SSX; SYT

Malignant rhabdoid tumor

Poorly differentiated neoplasms, with poorly differentiated cells, pleomorphic and eccentric nucleus, vesicular chromatin and a prominent nucleolus, with eosinophilic cytoplasm

INI 1 (-)

Loss of INI1

Neuroblastoma

Blue round cell tumor forming pseudo-rosettes

Synaptophysin (+) NSE (+)

N-MYC amplification

Ewing Sarcoma

Undifferentiated small, blue, round cells with scant cytoplasm and an inconspicuous nucleolus

CD99 (+) Fli1 (+) WT1 (-)

t(11; 22) EWS; ETS

Rhabdomyosarcoma

Blue round cell tumor, arranged in pseudoalveolar pattern or with presence of rhabdomioblats

Desmina (+) MyoD1 (+), Miogenin (+) WT1 (-)

t(2;13)PAX3-FOXO1

t(1;13) PAX7-FOXO1

(alveolar subtype)