Metastasis of gastrointestinal stromal tumor to skeletal muscle: a case report

Kayo Suzuki,Tomoatsu Kimura,Kenta Watanabe,Takeshi Hori,Masahiko Kanamori,Kaoru Nagao,Taketoshi Yasuda

doi:10.1186/1752-1947-8-256

Abstract

IntroductionGastrointestinal 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.Case presentationA 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.ConclusionsBecause 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.

Highlights

Gastrointestinal stromal tumor is the most common malignant mesenchymal tumor of the gastrointestinal tract
An excisional biopsy was performed and the tumor was diagnosed as a leiomyosarcoma composed of cellular bundles of spindle cells (Figure 1)
The buttock tumor cells were negative for c-KIT, but diffusely positive for platelet-derived growth factor receptor-α (PDGFRA) and were definitively diagnosed as a skeletal muscle metastasis of the primary small intestine gastrointestinal stromal tumor (GIST)

Summary

Conclusions

We present an extremely rare case of skeletal muscle metastasis from a GIST. To the best of our knowledge, there have been only three previously reported cases in the English literature of GIST metastasizing to skeletal muscle. Skeletal muscle metastases from GIST are rare, the likelihood of finding metastases in these unusual sites has increased due to the prolonged survival of patients with GIST after the introduction of imatinib therapy. We should recognize metastases of GISTs in the differential diagnosis for spindle cell tumors, as it is necessary to begin appropriate treatment in a timely fashion. Consent Written informed consent was obtained from the patient’s next-of-kin for publication of this case report and any accompanying images. Case Reference [No.] Age/Sex Primary site Location of muscle metastases (years)*

Introduction

Discussion

Findings

Present case