A two-month old baby boy is found to have a large left flank mass. He has hypertension, serum calcium of 12 mg/dL and microscopic hematuria. mesoblastic nephroma (CMN)​ is suspected, The CT imaging characteristics of congenital mesoblastic nephroma include:

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[size=20px]A peripheral crescent with subcapsular hemorrhage

 

B diffusely calcified mass

 

C solid/cystic mass with indistinct margins

 

D cyst with bony metastasis

 

E pseudocapsule with clear margins​[/size]

A

A

A

correct answer

C solid/cystic mass with indistinct margins

 

Renal tumors in infancy are uncommon. When present, they are increasingly diagnosed during the fetal period. Roughly three-quarters are congenital mesoblastic nephromas (CMN) and 25% are Wilms tumors or other varieties. After three months of age, Wilms is the most common tumor type. Both types will present with paraneoplastic symptoms such as hypertension and hypercalcemia. These associated problems resolve with resection of the tumor. Imaging characteristics of Wilms tumor include formation of a pseudocapsule with clear margins. Clear cell sarcoma is an aggressive tumor which frequently presents with bony metastasis and has a prominent cystic component. Rhabdoid tumor of the kidney is associated with subcapsular renal hemorrhage. Finally, ossifying renal tumors of infancy can often appear similar to a staghorn calculus.

 

CMN is the most common renal mass of infancy. It is most commonly a benign entity treated with resection alone. There are three types of CMN: classic (75%), cellular (16%) and mixed (9%).

 

The described CT imaging characteristics of CMN include indistinct margins, the intratumor pelvis, and a double-layer sign after contrast.

 

The classical type has an imaging and microscopic appearance similar to uterine leiomyoma. Resection alone is sufficient and recurrence is uncommon.

 

The cellular variety is heterogeneous and shows areas of hemorrhage and necrosis. In gross appearance, the cellular variant is soft and fleshy. Histologically, it shows high cellularity, mitoses, apoptotic cells and necrosis; features often noted in malignant tumors. Cellular varieties may behave in a malignant fashion, manifested by recurrence and metastases - typically within one year of resection. The cellular variant has a genetic footprint similar to that of an infantile fibrosarcoma and may require treatment with sarcoma-based chemotherapy protocols. The cellular variant will often have hypercalcemia as a complication due to a paraneoplastic syndrome.​

What about the mixed variant. Please outline the genetic footprint in details of cellular variety.