Table 2.
Characteristics of SSTR2 IHC-positive vs SSTR2 IHC-negative tumors
| SSTR IHC-positive PPGLs (n = 101) | SSTR IHC-negative PPGLs (n = 101) | |
|---|---|---|
| Tumor location | ||
| Pheochromocytoma | 79 (78.2%) | 87 (86.1%) |
| Paraganglioma (not head and neck) | 10 (9.9%) | 8 (7.9%) |
| Head and neck paraganglioma | 11 (10.9%) | 5 (5.0%) |
| Not available | 1 (1%) | 1 (1%) |
| Tumor size | ||
| >5 cm | 22 (21.8%) | 35 (34.7) |
| <5 cm | 56 (55.4%) | 61 (60.4%) |
| Not available | 23 (22.7%) | 5 (5.0%) |
| Clustera | ||
| 1A | 17 (16.8%) | 1 (1%) |
| 1B | 2 (2.0%) | 15 (14.9%) |
| 2 | 30 (29.7%) | 18 (17.8%) |
| No mutation | 22 (21.8%) | 19 (18.8%) |
| Incomplete sequencing | 30 (29.7%) | 48 (47.5%) |
| Ki-67 | ||
| Ki-67 ≥ 3% | 19 (18.8%) | 20 (19.8%) |
| Ki-67 < 3% | 73 (72.3%) | 67 (66.3%) |
| Not available | 9 (9.0%) | 14 (13.9%) |
| SDHB IHC positive | ||
| yes | 82 (81.2%) | 95 (94.1%) |
| No | 14 (13.9%) | 6 (5.9%) |
| Not available | 5 (5.0%) | — |
Abbreviations: IHC, immunohistochemistry; PPGL, pheochromocytoma and paraganglioma; SDHB, succinate dehydrogenase subunit B; SSTR, somatostatin receptor.
According to their mutation profile, PPGLs are divided into 3 main molecular clusters: (1) pseudohypoxia cluster (1A and 1B), (2) kinase-signaling cluster 2, and (3) Wnt signaling cluster 3. Cluster 1 is further divided into cluster 1A (mutations in the Krebs cycle associated genes) and 1B (mutations in the hypoxia-signaling pathway).