COL18A1 and sarcoma: In general, murine sarcomas with Rb1 nullizygosity were associated with the undifferentiated morphology, except for one case identified as aRMS which also showed lower expression of COL18A1, COL4A1, and PLOD2 compared to Rb1 wildtype sarcomas (p = 0.0035, 0.04, and 0.08, respectively).