Abstract
BackgroundThe concept of GIST was established in 1998, clearly differentiating between gastrointestinal leiomyosarcoma and GISTs among gastrointestinal mesenchymal tumors. Lymph node metastasis is extremely rare in true gastrointestinal leiomyosarcoma, and there are no reports of malignant transformation from leiomyoma.Case presentationThe patient was an old woman who had undergone endoscopic mucosal resection for an Is polyp on the left side of the transverse colon at the age of 73. She was diagnosed with leiomyoma with positive surgical margins. Subsequently, she presented to our institution with a sensation of pressure in the upper abdominal region as a chief complaint at the age of 76 years. Abdominal computed tomography and colorectal endoscopy showed a tumor lesion with invagination of the intestines in the transverse colon, the same site as that of the previously resected leiomyoma. A biopsy suggested a smooth muscle tumor, and we performed partial left transverse colectomy and lymph node dissection under a diagnosis of recurrence and enlargement of the previously incompletely resected leiomyoma. Histopathological examination revealed spindle-shaped tumor cells, and the mitotic activity was 30–40/10 high-power field. Tumor cells were immunohistologically positive for α-smooth muscle actin and h-caldesmon; partially positive for desmin; negative for c-kit, CD34, DOG-1, and the S-100 protein; and showed a Ki-67 labeling index of 70–80%. She was diagnosed with leiomyosarcoma malignantly transformed from leiomyoma. Metastasis was found in 1 of the 14 resected lymph nodes. The patient did not undergo adjuvant chemotherapy, but has survived with no recurrence at 2 years after the surgery.ConclusionsWe have reported a case of leiomyosarcoma of the transverse colon with lymph node metastasis that was malignantly transformed from a leiomyoma.
Highlights
The concept of Gastrointestinal stromal tumor (GIST) was established in 1998, clearly differentiating between gastrointestinal leiomyosarcoma and gastrointestinal stromal tumors (GISTs) among gastrointestinal mesenchymal tumors
We have reported a case of leiomyosarcoma of the transverse colon with lymph node metastasis that was malignantly transformed from a leiomyoma
Lymph node metastasis is extremely rare in true gastrointestinal leiomyosarcoma, and there are no reports of malignant transformation in leiomyoma of the colon
Summary
Since discovery of the c-kit gene mutation by Hirota et al in 1998 [1], gastrointestinal leiomyosarcomas have been recognized as distinct from gastrointestinal stromal tumors (GISTs), as opposed to their earlier classification. Total colonoscopy was performed at the time, showing that the polyp was located 50 cm from the anal verge and observing no other lesions. Immunohistological examination showed that the spindle-shaped tumor cells were positive for α-SMA and negative for c-kit and CD34. We diagnosed her with recurrence and enlargement of the leiomyoma that had been incompletely resected 3 years earlier based on the pathological similarities and occurrence site. Tumor cells were immunohistologically positive for α-SMA and h-caldesmon; partially positive for desmin; negative for c-kit, CD34, DOG-1, and the S-100 Based on these results, the patient was diagnosed with leiomyosarcoma of the transverse colon with lymph node metastasis, which occurred due to malignant transformation of the incompletely resected leiomyoma. She did not receive adjuvant chemotherapy during the followup period, but has survived without recurrence for two years
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