In the guidelines for the diagnosis and management of NF1, clinical symptoms mostly occur during childhood or adolescence, however our patient was diagnosed at the age of 48 due to sociocultural problems. Although it was not proven in our case, there was a positive family history. These findings meet the clinical and diagnostic criteria for NF1. In addition, the diagnosis was clarified with the genetic test. The most important feature of our patient is that it is a giant posterior mediastinal GIST case developing on the basis of NF1.
GISTs associated with NF1 are multiple and usually low-grade, typically affecting the jejunum, ileum, duodenum, and stomach (6). In the examination of 252 cases with GIST on the basis of NF1, it was reported that the patients were younger and the tumors were significantly smaller. In the same study, tumor localization is mainly located in the jejunum and ileum in the NF1 subgroup while it is in the stomach in the sporadic group. In addition, tumors in the NF1 subgroup were observed to have low risk criteria compared to sporadic GISTs (7). In addition, posterior mediastinal GIST case was extremely rare in the literature. In a recent literature review, a study where 12 GIST cases were reported after the diagnosis of posterior mediastinal mass indicated that most originated from the esophagus and 2 cases originated from the stomach. It has been reported to occur mostly in the elderly and present as giant masses (8). In our case, it is noteworthy that the mediastinal mass can reach giant dimensions at a younger age. To the best our knowledge, in the literature the current patient was the first case diagnosed with posterior mediastinal GIST developing on the basis of NF-1.
Due to the rarity of esophageal GISTs, the optimal surgical method is unclear. While enucleation is generally recommended for smaller tumors (2–5 cm in size), esophagectomy is recommended for GISTs larger than 9 cm (9). In our case, there was no esophageal invasion and a bulky mass was totally removed without the need for esophageal surgery. The optimal surgical method is not known, and there is not enough data on the risk of recurrence. In a study of 135 esophageal GIST cases, Feng et al. reported that 5-year DFS was 65.1% and disease-specific survival (DSS) was 65.9%.Tumor size was an independent risk factor for the prognosis of esophageal GISTs (10). Nakano et al. evaluated the data of 139 operated patients of 153 esophageal GIST patients reported in the literature and they found that 23 (16.5%) patients had recurrence, 5 (3.6%) of them have local recurrence and 18 (12.9%) of them have distant metastases. The average time to relapse was 40 months, 5-year disease-free survival (DFS) and overall survival (OS) were reported as 57% and 89%, respectively. They recommended long-term follow-up because, recurrence occurs even after years (11).
In patients with high-risk GIST three-year treatment with imatinib was recommended adjuvant treatment (12). R0 resection was performed in all 12 cases with a diagnosis of posterior mediastinal GIST. In 9 cases with follow-up data, the median follow-up period was 24 months and 8 patients were followed up without adjuvant therapy and without any disease (8). In one case, Constantinou S et al. started adjuvant imatinib treatment in a patient whose recurrence risk was evaluated as high (13). We considered our patient to be at high risk for recurrence due to the size of the tumor and initiated adjuvant imatinib treatment.