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Introduction: Congenital mesoblastic nephroma (CMN) is a mesenchymal neoplasm of the kidney that usually presents by the age of 6 months. It is the most common congenital renal neoplasm. Three histologic variants have been described - classic (25%), cellular (65%), and mixed (10%). It has excellent prognosis with 95% survival rate following complete resection.
The classic variant consists of intersecting fascicles of bland spindle cells (shown here) and resembles uterine leiomyomas and infantile fibromatosis. It lacks TRK fusion. The cellular variant resembles infantile fibrosarcoma and carries ETV6-NTRK fusion. The mixed variant, most likely a subtype of classic, lacks the TRK fusion.
The classic variant consists of intersecting fascicles of bland spindle cells (shown here) and resembles uterine leiomyomas and infantile fibromatosis. It lacks TRK fusion. The cellular variant resembles infantile fibrosarcoma and carries ETV6-NTRK fusion. The mixed variant, most likely a subtype of classic, lacks the TRK fusion.