Congenital Mesoblastic Nephroma
Histologic
features:
- 2
subtypes: cellular and “classic”
- cellular
subtype:
- densely
packed, plump spindle cells
- diffuse
sheets or interlacing bundles
- pushing
border with pseudocapsule which often consists
of squished classic subtype
- abundant
cytoplasm
- variably
enlarged, vesicular nuclei
- may
contain large nucleoli
- frequent
mitoses
- blue
cell variant resembles infantile fibrosarcoma
- “classic”
subtype:
- fascicles
and whorls of benign-appearing spindled myofibroblasts
resembling leiomyoma
- infiltrating
border with long tongues extending into kidney and soft tissue,
sometimes trapping tubules and glomeruli
- metaplastic elements in trapped
kidney are common: cartilage, extramedullary hematopoiesis, cuboidal metaplasia
- no
capsule
- advancing
edge into perirenal fat often shows angiomatous appearance
- few mitotic figures
Immunophenotype:
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Marker:
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Sensitivity:
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Specificity:
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Desmin
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Molecular features:
- cellular
subtype is often associated with t(12;15)(p13;q25)
- ETV6-NTRK3
fusion gene
- Also
seen in infantile fibrosarcoma (regarded as
the same entity now)