Kidney tumor
Childhood neoplasms
Congenital mesoblastic nephroma


Topic Completed: 1 December 2011

Revised: 19 September 2019

Copyright: 2003-2019, PathologyOutlines.com, Inc.

PubMed Search: Congenital mesoblastic nephroma [title] kidney

Mandolin S. Ziadie, M.D.
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Cite this page: Ziadie MS. Congenital mesoblastic nephroma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/kidneytumormesoblastic.html. Accessed December 13th, 2019.
Definition / general
  • Congenital myofibroblastic tumor that resembles infantile fibromatosis / leiomyoma (classic) or fibrosarcoma (cellular)
  • Also called fetal mesenchymal / leiomyomatous hamartoma
  • First described in 1967 (Pediatrics 1967;40:272)
Epidemiology
  • Most common pediatric renal tumor in infancy
  • 5% of all pediatric renal tumors (Cancer 2006;106:2275)
  • Age at presentation varies with type (classic, 16 days; cellular, 5 months; mixed, 2 months)
  • Rarely occurs in children older than 2 years of age
  • Frequency: 66% cellular, 24% classic and 10% mixed
Diagrams / tables

AFIP images

Age distribution curve

Clinical features
  • May present in utero with fetal hydrops / polyhydramnios
  • Excellent prognosis (5 year survival of 96%, Pediatr Blood Cancer 2008;50:1130)
  • 5% - 10% recur or metastasize (usually cellular type), usually by age 1 year to lung, brain or rarely bone
  • Poor prognostic factors include: cellular variant (Pediatr Surg Int 2007;23:205) and advanced stage or sinus / vascular involvement (margins and sinus / vascular involvement should be reported)
Case reports
Treatment
  • Nephrectomy with wide margins
  • Chemotherapy if resection is incomplete in infants 3 months or older, or if tumor ruptures during surgery
Gross description
  • Unilateral
  • Extensive sampling of margin should be performed
  • Classic: mean 5 cm, variably circumscribed, white / yellow whorled mass near hilum, involving over half of kidney with indistinct tumor kidney interface; resembles leiomyoma with whorled cut surface; may be cystic; may involve renal sinus; hemorrhage and necrosis uncommon
  • Cellular: mean 9 cm, necrosis and large cystic areas and hemorrhage
  • Mixed: mean 10 cm, cysts, hemorrhage and necrosis in cellular areas
Gross images

Case of the Week #57

Tan fleshy masses
with hemorrhage,
necrosis and cystic
degeneration



Images hosted on other servers:

Tan fleshy masses
with hemorrhage,
necrosis and cystic
degeneration

Rubbery solid
homogenous
tumor invades the
renal parenchyma

Microscopic (histologic) description
  • Classic: resembles infantile fibromatosis or leiomyoma with fascicles and whorls of bland spindled myofibroblasts and thin collagen fibers; tumor surrounds tubules and glomeruli, has irregular borders; chondroid metaplasia / dysplasia of the entrapped tubules is common; mitoses are rare; necrosis / desmoplasia are not present
  • Cellular: resembles infantile fibrosarcoma with a sheet-like proliferation of plump, atypical spindle cells with abundant cytoplasm, vesicular nuclei and nucleoli; frequent mitotic figures (25 - 30 / 10 HPF) and necrosis; the tumor has a pushing border
  • Mixed: tumors with a combination of the above features
Microscopic (histologic) images

AFIP images

Prominent interlacing bundles

Tumor interdigitates with renal parenchyma

Perirenal invasion
with angiomatous
vascular
proliferation


Embryonal metaplasia of Bowman capsule and entrapped tubules; #2 accompanied by epithelial hyperplasia

   

Extension into renal sinus
and along structures medial
to the kidney is an important
feature of most lesions



Cellular pattern:

Cellular and classic appearance

Mesoblastic Nephroma



Case of the Week #57

Well circumscribed tumor: low power

Medium power

High power

Infiltrative margin

Glomerular entrapment

Angiomatoid area



Images hosted on other servers:

Resembles fibromatosis

Mitotic figures

Cellular areas have
mitotic figures, cystic
degeneration, hemorrhage
and necrosis

Cytology description
Positive stains
Negative stains
Molecular / cytogenetics description
Differential diagnosis
  • Adult mixed epithelial and stromal tumor: mean age in 50s, usually women, similar morphology and staining pattern, also positive for estrogen and progesterone receptors
  • Clear cell sarcoma: similar age but has clear cells and chicken wire vasculature, tumor cells isolate single nephrons, fine nuclear chromatin and low mitotic rate; negative for smooth muscle markers
  • Metanephric stromal tumor: older age, nodular low power pattern, onion skin cuffing around entrapped renal tubules, heterologous differentiation and vascular changes, CD34+
  • Rhabdoid tumor: more invasive margins, usually epithelioid cells with cytoplasmic inclusions and prominent nucleoli, usually presents with metastases, INI1-
  • Wilms tumor: older age, also has blastema and nephrogenic rests; previously treated tumors may have well differentiated spindle cell stroma
Additional references
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