[108] DOG1 Rescues Most CD117-Negative GISTs: A Report from an Italian Multi-Institutional Study (REGISTER Study)
S Rossi, C Cantaloni, C Sartor, E Bragantini, L Messerini, I Bearzi, G Mazzoleni, C Capella, G Arrigoni, A Sonzogni, C Gnocchi, S Romeo, L Toffolatti, M Barbareschi, PG Casali, AP Dei Tos. General Hospital, Treviso, Italy; General Hospital, Trento, Italy; Firenze University School of Medicine, Firenze, Italy; Ancona University School of Medicine, Ancona, Italy; General Hospital, Bolzano, Italy; Ospedale di Circolo e Fondazione Macchi, Varese, Italy; Istituto Scientifico H S. Raffaele, Milano, Italy; Ospedali Riuniti, Bergamo, Italy; Novartis Farma, Sarcoma Unit, Origgio, Italy; IRCCS Istituto NazionaleTumori, Milano, Italy
Background: DOG1 is an emerging highly specific and sensitive immunohistochemical marker of GISTs. The aim of our study was to confirm the diagnostic utility of this antibody in a large Italian multi-institutional GISTs series (REGISTER) and in particular its ability to discriminate GIST from GISTs mimics.
Design: Immunohistochemistry for DOG1 (1:400, WB pH6, clone SP31, ACZON) was performed on 42 tissue microarray (TMA) slides, which included 583 CD117-positive GISTs and 45 CD117-negative GISTs. Furthermore 4 TMA slides containing 73 mesenchymal tumours of the GI tract, including 21 leiomyomas, 16 leiomyosarcomas, 12 pleomorphic sarcomas and 10 desmoid fibromatoses, were also immunostained.
Results: DOG1 immunostaining was positive in 574 (98.5%) of CD117-positive GISTs and in 37 (82.2%) of the CD117-negative GISTs. The majority of the positive cases (96.2%) showed a diffuse and strong staining (Table 1). Of the 73 GISTs mimics, only 2 smooth muscle tumors proved to be DOG1 positive (Table 2).
Conclusions: DOG1 is expressed in most of CD117-negative GISTs, indicating its higher sensitivity as GIST marker. As a small subgroup of CD117-positive GISTs failed to stain with DOG1, the combination of CD117 and DOG1 is highly recommended for the diagnosis of GIST in daily practice.
| N of cases | histotype | DOG1 +ve, N (%) | DOG1 -ve, N (%) |
| 21 | leiomyomas | 1 (4.8) | 20 (95.2) |
| 16 | leiomyosarcomas | 1 (6.2) | 15 (93.8) |
| 12 | pleomorphic sarcomas NOS | 0 | 12 (100) |
| 10 | desmoid fibromatoses | 0 | 10 (100) |
| 4 | spindle cell sarcomas | 0 | 4 (100) |
| 3 | schwannomas | 0 | 3 (100) |
| 6 | others | 0 | 6 (100) |
| N of GISTs cases | DOG1 +ve | DOG1 -ve | ||
| strong/diffuse | weak/focal | |||
| CD117 +ve GISTs | 583 | 555 (95.2%) | 19 (3.3%) | 9 (1.5%) |
| CD117 -ve GISTs | 45 | 33 (73.3%) | 4 (8.9%) | 8 (17.8%) |