A 74 year-old man with a longstanding history of chronic gastritis and effective eradication of Helicobacter pylori, presented with aggravated heartburn and dysphagia at the level of the xiphisternum for five years. After several upper GI endoscopies showing mild atrophic gastritis in the antrum, had a computerised tomography that revealed a 4 x 3 x 3 cm low-density nodule containing a small focus of calcification arising from the posterior wall of the gastric fundus, suspicious of an exophytic GIST (Fig. 1). The case was discussed in a sarcoma multidisciplinary meeting with a consensual decision to proceed to surgery due to tumour size and symptoms. The patient underwent laparoscopic excision of the GIST and was discharged after five days of operation. He remained disease free after five months of follow up and did not receive adjuvant treatment. There was no history of NF-1 or other relevant family history.
The resection specimen was composed of a gastric wall measuring 5.5 x 4 x 3.5 cm. There were two papillary tumour masses lightly adherent to the serosal surface, the larger measuring 4 x 3 x 3 cm and the smallest 3 x 3 x 2.5 cm, both part of a single mass that fragmented during contraction on removal and fixation. There was one separate firm, white nodule measuring 0.8 x 0.7 x 0.4 cm on the serosa and involving the muscularis propria, 3.5 cm from the margin (Fig. 2).
Both the large and the smaller visible nodules had identical morphology, with compact arrangements of relatively uniform spindle cells with elongated nuclei, inconspicuous nucleoli and small, well-defined paranuclear cytoplasmic vacuoles. There was no necrosis. The tumours were covered by an intact peritoneal surface. The mitotic index was 4 per 50HPF. In addition, the Ki67 index, discounting infiltrating lymphoid cells, was 2.5% in the larger tumour and 6% in the smaller nodule.
There was very subtle diffuse infiltrative component within the muscularis propria, highlighted on the immunohistochemistry for DOG1 and CD117 (Fig. 3). The tissue immediately adjacent to the staple line contained a further microscopic focus of GIST ('tumorlet') measuring 0.7 x 0.3 mm (Fig. 4).
Additional staining with CD117 and DOG1 demonstrated a markedly increased density of immunoreactive cells in the apparent uninvolved muscularis propria in the vicinity of the peduncle of the large tumour.
Using capillary electrophoresis single-strand conformation analysis (CE-SSCA), a deletion involving codon 560 in c-KIT exon 11 (c.1679_1681del p.-Val560del) was detected in both the solid and the diffuse components. This result was confirmed on a second, independent investigation. There was no detectable mutation in the PDGFRA gene.