86% of GNAS-mutated non-mucinous adenocarcinomas (6/7) were positive for TTF-1 immunohistochemistry, while only 25% of GNAS-mutated IMAs (1/4) were positive for TTF-1.
GNAS mutations were detected in two LAMNs and in one MAC, although the GNAS mutation in this MAC was a nonsense mutation (Q227X) expected not to be activating mutation.
GNAS mutations (p.R201H, c.602G>A and p.R201C, and c.602C>T) were identified in 17 (31%) of 55 of disseminated mucinous neoplasms and were found in 8 (35%) of 23 low-grade mucinous neoplasms, 7 (37%) of 19 high-grade mucinous adenocarcinomas lacking a signet ring cell component, and 2 (15%) of 13 high-grade mucinous adenocarcinomas with a signet ring cell component.
Activating GNAS mutations were found in 8 of the 19 lobular endocervical glandular hyperplasias (LEGH; 42%) and 4 of the 79 endocervical-type mucinous adenocarcinomas (5%) but were never seen in the normal endocervical tissue, minimal deviation adenocarcinomas, endometrioid adenocarcinomas, or squamous cell carcinomas.
This patient had been operated on for an unusually large invasive colloid adenocarcinoma (pT3N0M0 R0) derived from an intestinal subtype GNAS-mutated IPMN.
A mutational analysis identified activating GNAS mutations in 16 of 32 low-grade appendiceal mucinous neoplasms (LAMNs) but in none of three mucinous adenocarcinomas (MACs).