CD99 and cancer: BRCA1 basal cancers, when compared to sporadic basal cancers showed reduced positivity for FOXP1 (6/20 [30 %] vs. 37/49 [76 %], p < 0.001), cyclin D1 (8/22 [36 %] vs. 30/46 [65 %], p = 0.025), NRP1 (2/20 [10 %] vs. 23/46 [50 %], p = 0.002) and CD99 (17/20 [85 %] vs. 7/19 [37 %], p = 0.002) (Table 3, Additional file 5: Figure S4).