Rare cause of cystic liver lesions: Liver metastasis of gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal neoplasms of the gastrointestinal tract with an annual incidence of 1–2 per 10 000 people. Although most GISTs are solid, they may present with predominantly cystic components. A 69‐year‐old Japanese woman presented with a recently elevated gamma‐glutamyl transpeptidase level. Computed tomography revealed multiple space‐occupying lesions (SOLs) in the liver. These SOLs appear cystic on magnetic resonance imaging and abdominal ultrasound and are associated with thick walls at the margins. In addition, these thick walls showed high intensity on diffusion‐weighted images. She was diagnosed with liver metastasis of GIST by diagnostic biopsies from the thick parts of the cystic liver lesion (thick walls at the margins). The primary lesion was thought to be located along the medial side of the descending part of the duodenum, but a duodenal biopsy was initially undiagnosed. Liver metastases due to GISTs are known to cause cystic changes after treatment, such as imatinib mesylate. However, to the best of our knowledge, only six cases where hepatic GIST with predominantly cystic changes (prior to any treatment) have been reported. It should be noted that GISTs appear cystic in all organs.