Fig. 1.

Photomicrographs illustrating frequently observed PASS and GAPP parameters in MEN 2A-associated PCCs. a Case 9 (MEN 2A PCC) demonstrating large, irregular nests. This was the most frequently fulfilled PASS criteria and the second most common GAPP criterion in our MEN 2A cohort. Image at × 100 magnification. b Case 27 (sporadic control) displaying a classical, alveolar growth pattern (“zellballen”) as comparison. Image at × 100 magnification. c Case 4 (MEN 2A PCC) displaying a Ki-67 index of 2.5%. Elevated Ki-67 index was the most frequently observed GAPP criterion among the MEN 2A cases. d Case 33 (sporadic control) demonstrating a Ki-67 index of < 1% as comparison. e Pie charts showing the ratio of cases with GAPP scores ≥ 3 and PASS ≥ 4 in the group of sporadic PCCs (n = 28) and in the MEN 2A group (n = 13)