B3GLCT and popliteal pterygium syndrome: The two most striking clonally exclusive pathway pairs, i.e., pathways that are aberrated in different clones of the same tumour in a mutually exclusive fashion, are “major pathway of rRNA processing in the nucleolus and cytosol” (referred to as pathway 1), “O-glycosylation of TSR domain-containing proteins” (pathway 2)}, and pathway 1, “defective B3GALTL causes Peters-plus syndrome (PpS)” (pathway 3), which are clonally exclusive in both patients in which they are affected (Figure 4A,B, Supplementary Table S3), namely, patients 8 and 14 (p < 10−5).