Mesoblastic nephroma (also sometimes known as a congenital mesoblastic nephroma (CMN) or fetal renal hamartoma) is in general a benign renal tumour. It typically occurs in utero or in infancy.
It is the commonest neonatal renal tumour. Diagnosis is usually in the antenatal period or immediately after birth. The tumour can account for ~3-6% of all renal neoplams in children 3,7. Approximately 50% occur during the neonatal period and 80% of cases are reported within the first month of life.
Most common clinical presentation is a palpable abdominal mass, with haematuria occurring less frequently.
It is a mesenchymal tumour. Macroscopically the tumour is a solid un-encapsulated mass which often occurs near the renal hilum. It tends to invade the surrounding structures and renal parenchyma. Haemorrhage and necrosis are infrequent. Histologically, it is typically composed of connective tissue growing between nephrons, usually replacing most of the renal parenchyma.
The classic cytological description of the lesion is that of cellular clusters of spindle cells, mild nuclear pleomorphism, mitotic activity and no blastema.
There are two main pathological variants:
- classic mesoblastic nephroma
cellular mesoblastic nephroma
- more heterogeneous in appearance on imaging
- tends to be larger and presents later in infancy
- may exhibit aggressive behaviour including vascular encasement and metastasis 5
Non specific and not an imaging modality of choice but if performed incidentally in a neonate, may demonstrate a soft tissue mass displacing bowel. Calcification is rare 3.
Sonographic appearance can vary depending on the pathological variant 6. In general it is a well-defined mass with low-level homogeneous echoes. The presence of concentric echogenic and hypoechoic rings can be a helpful diagnostic feature. A more complex pattern due to haemorrhage, cyst formation and necrosis can also be seen and tends to favour the cellular variant. Colour Doppler interrogation may show increased vasculairty
Antenatal ultrasound may also show evidence of associated polyhydramnios.
Usually not performed in an antenatal situation. Solid hypoattenuating renal lesion with variable contrast enhancement. Cystic areas, necrosis, and haemorrhage are uncommon(only in cellular type)5. Typically no calcification seen.
Best modality for cross sectional imaging antenatally and can better assess anatomical relationships.
Unless complicated necrosis and haemorrhage (both generally uncommon), general signal characteristics within the mass include:
- T1: homogeneously hypointense 8
- T2: homogeneously hypointense 8
Potential complications with large tumours include:
Treatment and prognosis
The majority are benign tumours and have a favourable outcome. The cellular variant can at times be aggressive. As a surgical option, a nephrectomy usually suffices as treatment.
- 1. Hartman DS, Lesar MS, Madewell JE et-al. Mesoblastic nephroma: radiologic-pathologic correlation of 20 cases. AJR Am J Roentgenol. 1981;136 (1): 69-74. AJR Am J Roentgenol (abstract) - Pubmed citation
- 2. Kirks DR, Kaufman RA. Function within mesoblastic nephroma: imaging--pathologic correlation. Pediatr Radiol. 1989;19 (2): 136-9. - Pubmed citation
- 3. Wootton SL, Rowen SJ, Griscom NT. Pediatric case of the day. Congenital mesoblastic nephroma. Radiographics. 1991;11 (4): 719-21. Radiographics (citation) - Pubmed citation
- 4. Gupta R, Mathur SR, Singh P et-al. Cellular mesoblastic nephroma in an infant: report of the cytologic diagnosis of a rare paediatric renal tumor. Diagn. Cytopathol. 2009;37 (5): 377-80. doi:10.1002/dc.21028 - Pubmed citation
- 5. Bayindir P, Guillerman RP, Hicks MJ et-al. Cellular mesoblastic nephroma (infantile renal fibrosarcoma): institutional review of the clinical, diagnostic imaging, and pathologic features of a distinctive neoplasm of infancy. Pediatr Radiol. 2009;39 (10): 1066-74. doi:10.1007/s00247-009-1348-9 - Pubmed citation
- 6. Chaudry G, Perez-atayde AR, Ngan BY et-al. Imaging of congenital mesoblastic nephroma with pathological correlation. Pediatr Radiol. 2009;39 (10): 1080-6. doi:10.1007/s00247-009-1354-y - Pubmed citation
- 7. Campagnola S, Fasoli L, Flessati P et-al. Congenital cystic mesoblastic nephroma. Urol. Int. 1998;61 (4): 254-6. Urol. Int. (link) - Pubmed citation
- 8. Prasad SR, Humphrey PA, Menias CO et-al. Neoplasms of the renal medulla: radiologic-pathologic correlation. Radiographics. 25 (2): 369-80. doi:10.1148/rg.252045073 - Pubmed citation
- 9. Lowe LH, Isuani BH, Heller RM et-al. Pediatric renal masses: Wilms tumor and beyond. Radiographics. 20 (6): 1585-603. Radiographics (full text) - Pubmed citation
- 10. Gupta R, Mathur SR, Singh P et-al. Cellular mesoblastic nephroma in an infant: report of the cytologic diagnosis of a rare paediatric renal tumor. Diagn. Cytopathol. 2009;37 (5): 377-80. doi:10.1002/dc.21028 - Pubmed citation
Synonyms & Alternative Spellings
|Synonyms or Alternative Spelling||Include in Listings?|
|Congenital mesoblastic nephroma||✗|
|Fetal renal hamartoma||✓|
|Congenital mesoblastic nephroma (CMN)||✗|
|Congenital mesoblastic nephroma : general||✗|
|Mesoblastic nephroma : general||✗|
|Renal leiomyomatous hamartoma||✗|