Fig. 3.

Analysis of expected vs. observed tagged events indicates MML are not of β cell origin. (A and B) Lesions observed in HPAP/PAS double stains (magenta, mucin). (C and D) Lesions additionally identified in serial Alcian blue stains (turquoise, mucin). (A and C) Colored bars show the number of lesions observed. Gray bars show the expected/hypothesized number of HPAP⁺ events. Black bars represent the number of observed HPAP⁺ lesions. The number of observed events is far lower than the number of expected events. The likelihood that this distribution occurred by chance is extremely low (∗, binomial P < 0.000001). (B) HPAP/PAS stains show strong β cell tagging (blue) within islets and complete absence of labeling in MML. (C and D) The majority of MML observed in A and B also stain with Alcian blue, supporting metaplasia. (Scale bar, 100 μm.)