Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal tumors of gastrointestinal tract. The most common sites of metastases are the liver and the peritoneum, whereas breast metastases from GIST are extremely rare. We present a second case of GIST breast metastasis.

We found a case of breast metastasis from rectum GIST. A 55-year-old female patient presented with rectum tumor with multiply liver lesions and metastasis in the right breast. Abdominal-perineal extirpation of rectum was performed, histology and immunohistochemistry study showed GIST, mixed type with CD117 and DOG-1 positive staining. The patient was taking imatinib 400 mg for 22 mo with stable disease. Because of growth of the breast metastasis the treatment was changed twice: The dose of imatinib was doubled with further progression in the breast lesion and then the patient was receiving sunitinib for 26 mo with partial response in the right breast and stable disease in the liver lesions. The breast lesion increased and right breast resection was done – surgery on local progression, the liver metastases were stable. Histology and immunohistochemistry studies revealed GIST metastasis, CD 117 and DOG 1 positive with KIT exon 11 mutation. After surgery the patient resumed imatinib. Until now the patient has been taking imatinib 400 mg for 19 mo without progression, last follow up was in November 2022.

GISTs breast metastases are extremely rare, we described the second case. At the same time second primary tumors have been reported frequently in patients diagnosed with GISTs and breast cancer is one of the most common second primary tumors in patients with GISTs. That is why it is very important to distinguish primary from metastatic breast lesions. Surgery on local progression made it possible to resume less toxic treatment.

• Gastrointestinal stromal tumors
• Metastases
• Breast
• Limited progression
• Case report

Gastrointestinal stromal tumors (GISTs), which are the most common soft tissue tumors of the gastrointestinal tract, originate from Cajal interneurons. The main metastatic sites of GISTs are the liver and intra-abdominal cavity, and metastasis to the heart is rare.

The patient was a 78-year-old man who was diagnosed with a rectal GIST 20 years previously. Since then, he had undergone repeated operations for metastasis. A follow-up thoracoabdominal computed tomography scan 4 months prior to the operation revealed GIST metastasis to the left ventricular myocardium. The patient wanted the tumor removed and consequently underwent an operation. The surgical findings showed a 3-cm × 3-cm mass in the lateral wall of the left ventricle. The mass was resected from the left ventricular wall in the shape of a tear drop. The left ventricular cavity was closed with a 4–0 polypropylene mattress suture and continuous suture. Postoperative histopathological findings showed nodular tumor growth consisting of bundles of spindle-shaped cells in the myocardium. The margins were negative. Immunostaining showed c-KIT (CD17) positivity and CD34 positivity, consistent with GIST metastasis.

This case involved GIST metastasis to the heart muscle, which has rarely been reported worldwide.

• GIST
• Gastrointestinal stromal tumor
• Heart tumor
• Myocardial tumor

• adrenal metastatic tumor
• gastrointestinal stromal tumor
• primary adrenal lymphoma

• gastrointestinal stromal tumors
• skeletal muscle metastasis
• whole exome sequencing

• Drug Resistance, Neoplasm/genetics
• Gastrointestinal Neoplasms/drug therapy
• Gastrointestinal Neoplasms/pathology
• Gastrointestinal Stromal Tumors/drug therapy
• Gastrointestinal Stromal Tumors/pathology
• Humans
• Imatinib Mesylate/therapeutic use
• Male
• Middle Aged
• Muscle Neoplasms/drug therapy
• Muscle Neoplasms/secondary
• Muscle Neoplasms/surgery
• Muscle, Skeletal/pathology
• Sunitinib/therapeutic use
• Thigh/pathology
• Exome Sequencing

Gastrointestinal stromal tumours are rare tumours of the gastrointestinal tract (GIT) accounting for 0.1%–3% of all gastrointestinal tumours. The most common location is the stomach (55%) followed by the small bowel (31.8%), colon (6%), other various locations (5.5%), and the oesophagus (0.7%). They may also occur in extraintestinal locations. The signs and symptoms of GIST depend on the tumour's location and size. Gastrointestinal bleeding is one of the most common symptoms. Other signs and symptoms include abdominal discomfort, pain or distention; intestinal obstruction, and weight loss. The association between the development of GISTs and neurofibromatosis 1 (NF1) has been established. NF1-associated GISTs tend to have a distinct phenotype, and the absence of KIT/PDGRFα mutations in turn has implications on further management when they do not respond well to imatinib treatment. Here, we present one of the largest GISTs reported in the literature with a total volume of 25.3 × 20 × 14 cm + 27.9 × 23 × 8 cm and an overall weight of 7.3 kg, which developed in a 43-year-old female patient with NF1 and was resected on an emergency basis due to the rapid deterioration and development of abdominal compartment syndrome. Pathology assessment showed a malignant GIST composed of spindle cells with elongated nuclei with necrosis, marked pleomorphism and numerous giant cell. The mitotic count was >15/50 HPF, Ki 67 was 80%, and the lymphovascular invasion was clear. Immunohistochemistry investigations showed that Vimentin, CD117, and DOG1 were positive, while BCL-2 and CD99 were focal positives. Pan-CK, S-100, CD34, Desmin, SMA, and HMB-45 were negatives.

• cardiac tumor
• gastrointestinal stromal tumor

• Bilateral annexiectomy
• GIST
• Hysterectomy
• Ovarian metastases

Gastrointestinal stromal tumors (GISTs) are the most common malignant mesenchymal tumors of the gastrointestinal tract. The most common sites of metastasis are the liver and the peritoneum, whereas metastasis to soft tissue is rare. The authors present the case of a 78-year-old male with a soft tissue metastasis of a GIST and the current literature is reviewed.

• biopsy
• extragastrointestinal stromal tumors
• pleura
• thoracoscopy

• Gastrointestinal stromal tumor (GIST)
• bone
• metastasis

• Brachialis muscle
• Distant recurrence
• Gastrointestinal stromal tumor
• Skeletal metastasis
• Tyrosine kinase inhibitor

• Aged, 80 and over
• Antigens, CD34/analysis
• Biomarkers, Tumor/analysis
• Biopsy
• Female
• Gastrointestinal Stromal Tumors/chemistry
• Gastrointestinal Stromal Tumors/secondary
• Gastrointestinal Stromal Tumors/surgery
• Humans
• Immunohistochemistry
• Magnetic Resonance Imaging
• Muscle Neoplasms/chemistry
• Muscle Neoplasms/drug therapy
• Muscle Neoplasms/secondary
• Muscle, Skeletal/chemistry
• Muscle, Skeletal/pathology
• Positron-Emission Tomography
• Proto-Oncogene Proteins c-kit/analysis
• Stomach Neoplasms/chemistry
• Stomach Neoplasms/pathology
• Stomach Neoplasms/surgery
• Time Factors
• Treatment Outcome
• Tumor Burden
• Upper Extremity

• Adrenal Gland Neoplasms/diagnostic imaging
• Adrenal Gland Neoplasms/secondary
• Bone Neoplasms/diagnostic imaging
• Bone Neoplasms/secondary
• Female
• Fluorine Radioisotopes
• Fluorodeoxyglucose F18
• Gastrointestinal Stromal Tumors/diagnosis
• Gastrointestinal Stromal Tumors/diagnostic imaging
• Gastrointestinal Stromal Tumors/secondary
• Humans
• Intestinal Neoplasms/diagnosis
• Intestinal Neoplasms/diagnostic imaging
• Intestinal Neoplasms/pathology
• Liver Neoplasms/diagnostic imaging
• Liver Neoplasms/secondary
• Lung Neoplasms/diagnostic imaging
• Lung Neoplasms/secondary
• Male
• Neoplasm Staging/methods
• Peritoneal Neoplasms/diagnostic imaging
• Peritoneal Neoplasms/secondary
• Positron Emission Tomography Computed Tomography/methods
• Radiopharmaceuticals

Gastrointestinal stromal tumor is the most common malignant mesenchymal tumor of the gastrointestinal tract. The most common sites of metastasis are the liver and the peritoneum, but gastrointestinal stromal tumors rarely metastasize to the skeletal muscles. Only three cases of gastrointestinal stromal tumor metastasizing to skeletal muscle have been reported in the English literature. Here we present an additional case of skeletal muscle metastasis, and the relevant literature is reviewed.

A 54-year-old Japanese man presented with a three-month history of an enlarging mass of the left buttock. An excisional biopsy was performed and the tumor was diagnosed as a leiomyosarcoma. However, careful examination of the gastrointestinal tract revealed a tumor located in the small intestine. Surgical resection of the small intestine tumor was performed; histopathological and immunohistochemical examinations identified it as a primary gastrointestinal stromal tumor arising from the small intestine. Despite receiving both chemotherapy and molecular-targeted therapy, our patient died of gastrointestinal bleeding six months after the initial diagnosis.

Because it is a mesenchymal tumor, it is difficult to distinguish a gastrointestinal stromal tumor metastasis to skeletal muscle from other primary soft tissue sarcomas. Although metastasis of gastrointestinal stromal tumor to skeletal muscle is rare, the likelihood of finding metastases in these unusual sites is increasing due to prolonged survival of patients with gastrointestinal stromal tumor after the introduction of imatinib therapy. We should include metastases of gastrointestinal stromal tumors as differential diagnosis of spindle cell tumor, and it is necessary to begin appropriate treatment early.