Diagnostics challenges of gastrointestinal stromal tumours (GISTs) – tumours that mimic GISTS


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Nadeera De Silva1, Amy Kwan1, Daniel Holyoake1, Han Wong1, Ramesh Bulusu1
1Addenbrooke's Hospital, Cambridge, UK

Background

GISTS are the most common mesenchymal tumours of the gastrointestinal tract. Many tumours resemble GISTs on imaging or histology and misdiagnosis can be devastating as the prognosis of the ‘GIST mimics' can vary dramatically. We present our experience with GIST mimics from the Cambridge GIST Study group database.

Method

All patients who were discussed in the GIST specialist multidisciplinary meeting and were found to have a different tumour after central review of all imaging and post surgical histology were included in the study. Patient demographics, site of tumour, histology and treatments were extracted from the database. We present the clinical, radiological and histological characteristics of GIST mimics from the Cambridge database.

Results

43 patients with GIST mimics were identified. Males 24, females 19. Age range 12-85 years. The most common locations were stomach or gastro-oesophageal junction (46.5%), and the small bowel (25.6%), followed by rest of the gi tract, liver, pancreas and pelvis. The mean size was 8.79cm (range 0.5-27.5 cm).

The most common mimic of GISTs was leiomyosarcoma (18.6%), followed by leiomyoma (14 %). 30% of these GIST mimics had an aggressive histology including leiomyosarcoma, poorly differentiated adenocarcinoma, metastatic melanoma, inflammatory myofibroblastic tumour and clear cell sarcoma. 11.6% had benign histology and 58.4% had more indolent tumours including desmoid, solitary fibrous tumours, and neuroendocrine tumours.

Conclusion

The most common GIST mimic is leiomyosarcoma has a different treatment algorithm and has worse prognosis. This highlights the importance of making a GIST diagnosis following a comprehensive central review of radiology, histology including specialist immunophenotyping and mutational analysis within a specialist multidisciplinary setting.