Lauren N. Hendrix, MD
Stephen E. Strup, MD, FACS
BASICS
DESCRIPTION
• Congenital mesoblastic nephroma (CMN) is a renal tumor arising from nephrogenic mesenchyme
• Usually a solid lesion, but cystic varieties have been reported
• Majority are benign with a favorable prognosis
• First reported in 1967, referred to in older literature as Bolande’s tumor or Bolande disease
EPIDEMIOLOGY
Incidence
• Most common real tumor in children <6 mo of age, usually diagnosed prior to 3 mo
• Accounts for 3–10% of all pediatric renal neoplasms (1)
• More common in males (1)
• Usually unilateral
• Often detected prenatally by ultrasound
Prevalence
N/A
RISK FACTORS
Genetics
• ETV6-NTRK3 gene fusion
– Results from translocation t (12;15) (p13;q25)
– Found only in the cellular variant
– Also found in congenital fibrosarcoma (2,3)
PATHOPHYSIOLOGY
• Tumor classification
– Stage I: Tumor limited to kidney without involvement of capsule or hilar vessels
– Stage II: Tumor extends beyond capsule with invasion into perinephric fat or blood vessels, but margins of resection are negative
– Stage III: Tumor not completely resectable, tumor spillage occurs at time of resection, or tumor was biopsied preoperatively
– Stage IV: Hematogenous metastases or lymphatic spread outside of abdomen
– Stage V: Bilateral tumors
ASSOCIATED CONDITIONS
• Polyhydramnios
• Hydrops fet alis
DIAGNOSIS
HISTORY
• History of prenatal ultrasound finding of unilateral renal mass
• History of polyhydramnios
• Neonate with abdominal mass
• Hematuria, jaundice, hypertension, anemia, hypercalcemia
PHYSICAL EXAM
• Palpable abdominal mass
• Hematuria
• Jaundice
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• Complete blood count
• Basic metabolic panel
– Serum creatinine
– Serum calcium
• Urinalysis
Imaging
• Abdominal ultrasound
– Preferred modality
– “Ring pattern”
Hypoechoic mass with hyperechoic rim signifying vessels at the tumor periphery
Seen only in the classic variant
– Homogeneous or heterogeneous solid mass seen in cellular variant
• CT
– Homogeneous mass
– May have peripheral enhancement or focal enhancement at sites of hemorrhage or necrosis
• MRI
– Signal similar to normal parenchyma with exception of areas of hemorrhage (4)
Diagnostic Procedures/Surgery
• Biopsy
– The role of biopsy in pediatric renal tumors is controversial as nephrectomy is the mainstay of treatment and preoperative biopsy upstages to stage III
Pathologic Findings
• Three histologic subtypes
– Classic
1/3 of cases
Similar macro- and microscopically to leiomyoma
Entrapped nephrons and blood vessels seen at the tumor periphery
Not associated with metastasis
– Cellular
2/3 of cases
More aggressive than classic with high mitotic index and atypical growth pattern
Associated with local invasion/recurrence and metastasis
– Mixed (3)
DIFFERENTIAL DIAGNOSIS
• Solid renal mass
– Wilms tumor
– Rhabdoid tumor
– Metanephric adenofibroma
– Renal cell carcinoma
– Angiomyolipoma
– Clear cell sarcoma
– Multilocular cystic nephroma
• Autosomal recessive polycystic kidney disease
• Cross-fused ectopia
• Renal vein thrombosis
• Solitary kidney with compensatory hypertrophy
• Beckwith–Weidemann syndrome
• Adrenal mass
• Retroperitoneal mass (3)
TREATMENT
GENERAL MEASURES
• Management of associated features
– Hypertension
– Hypercalcemia
– Jaundice
– Anemia
• Chemotherapy reserved for patients >3 mo with cellular variant, tumor spillage at resection, microvascular invasion, metastatic disease, and inoperable tumors
MEDICATION
First Line
• Vincristine, cyclophosphamide, and doxorubicin (VCD)
• Vincristine, doxorubicin, and actinomycin D (VDA)
Second Line
• Isophosphamide, carboplatin, etoposide (ICE)
– Has considerable nephrotoxicity (3)
SURGERY/OTHER PROCEDURES
• Radical nephrectomy
– Gold standard
– Allows for appropriate staging
– Decreased risk of local recurrence
• Partial nephrectomy
– Has been reported with success in Wilms tumors but not CMN
ADDITIONAL TREATMENT
Radiation Therapy
No defined role
Additional Therapies
N/A
Complementary & Alternative Therapies
N/A
ONGOING CARE
PROGNOSIS
• Radical nephrectomy generally curative
• Classic variant favorable
• Metastases and local recurrence possible with cellular type, but rare
• Risk factors for recurrence: Cellular variant, older patient age, tumor spillage during resection, and positive surgical margins (3)
COMPLICATIONS
• Prenatally
– Polyhydramnios
– Hydrops fet alis
– Intrauterine fet al demise
• After birth
– Hypertension
– Hemodynamic instability
– Respiratory distress
FOLLOW-UP
Patient Monitoring
Regular abdominal ultrasound for 1 yr in classic variant and longer in cellular variant
Patient Resources
www.cancer.gov/cancertopics/pdq/treatment/wilms/Patient
REFERENCES
1. England RJ, Haider N, Vujanic GM, et al. Mesoblastic nephroma: A report of the United Kingdom’s Children’s Cancer and Leukaemia Group (CGLG). Pediatr Blood Cancer. 2011;56:744–748.
2. Mallya V, Arora R, Gupta K, et al. Congenital Mesoblastic Nephroma: A rare pediatric neoplasm. Turkish J Path. 2013;29:58–60.
3. Ahmed HU, Arya M, Levitt G, et al. Part II: Treatment of primary malignant non-Wilms’ renal tumors in children. Lancet Oncol. 2007;8:842–848.
4. Sheth MM, Cai G, Goodman TR, et al. AIRP best cases in radiologic-pathologic correlation: Congenital mesoblastic nephroma. Radiographics. 2012;32:99–103.
ADDITIONAL READING
McKenna PH, Ferrer FA. Prenatal and postnatal urologic emergencies. In: Docimo SG, ed. The Kelalis-King-Belman Textbook of Clinical Pediatric Urology. 5th ed. London: Informa Healthcare, 2007.
See Also (Topic, Algorithm, Media)
• Renal Mass
• Wilms Tumor (Nephroblastoma)
CODES
ICD9
236.91 Neoplasm of uncertain behavior of kidney and ureter
ICD10
• D41.00 Neoplasm of uncertain behavior of unspecified kidney
• D41.01 Neoplasm of uncertain behavior of right kidney
• D41.02 Neoplasm of uncertain behavior of left kidney
CLINICAL/SURGICAL PEARLS
• Most common solid renal tumor <6 mo of age.
• Radical nephrectomy is generally curative.