DISCUSSION
Sarcomas are malignant mesenchymal tumors and are divided into osteosarcomas and soft-tissue sarcomas. Gastrointestinal sarcomas are more common in the small intestine, stomach, and esophagus, and they occur mainly in older adults and less commonly in younger patients.5 The most common clinical manifestations, in order, have been reported to be abdominal pain, abdominal mass, and fever.6,7 Undifferentiated sarcoma, a soft-tissue sarcoma first described and named by Ozzello et al.,8is a high-grade, poor prognosis disease with a reported median survival of < 6 months.9 Conversely, there have been reports of SCS occurring intraperitoneally. However, there have been no previous reports of SCS occurring intracolonally or at the anastomotic site (as observed in this case), making the current report the first of its kind.
As part of the body’s natural response to soft tissue injury, spindle cells in injured tissue divide to promote healing. Normally, the spindle cells stop replicating once the affected area is healed. However, for reasons that are not fully understood, cells may continue to divide uncontrollably. Excess cells may then accumulate and combine to form an SCS. Risk factors include Paget’s disease of the bone, previous radiation therapy for bone infarction, and osteomyelitis. Encapsulated fluid retention and scattered small nodules, which had spontaneously disappeared preoperatively, could not be seen intraoperatively in the abdominal cavity, and the nodules that were submitted to pathology were only inflammatory changes. When the abdominal cavity and the nodules were present, they were accompanied by a mildly elevated inflammatory response. However, the inflammatory response improved when the abdominal cavity and the nodules disappeared after follow-up. Thus, we judged this to be most likely an inflammatory reaction. The cause of the inflammation is unknown, but this inflammation may have also contributed to this condition. We hypothesized that chronic inflammation and regeneration of the previous intestinal anastomosis contributed to this risk.
SCS is a group of tumors morphologically composed of spindle-shaped cells, such as fibrosarcoma, synovial sarcoma, and malignant nerve sheath tumors. A diagnosis is difficult to make based on morphology alone. The final diagnosis is based on immunostaining and genetic testing. In the present case, the diagnosis was possible only with immunostaining. The tumor developed at the anastomotic site, and carcinoma sarcomatoid changes were first considered. However, this was ruled out because there was no clear evidence of carcinoma, and AE1/AE3 testing was negative. Other results from immunostaining indicated high malignancy and suggested a high-grade SCS. Although the tumor originated within the intestinal wall, GIST and leiomyosarcoma were also ruled out because of differences in histology. Synovial and clear cell sarcomas were also excluded, leading to a sarcoma diagnosis with an unknown differentiation direction.
In contrast, cells were positive for MDM2 and CDK4. This suggested the possibility of a dedifferentiated component in dedifferentiated liposarcoma (DLPS). In such cases, a well-differentiated liposarcoma (WLPS) component is often present in the surrounding areas. In the present case, no WLPS component was found in the excised specimen. There was a preoperative history of fluid retention and spontaneous disappearance of the nodule. Although spontaneous resolution of WLPS has not been previously reported, spontaneous resolution of tissue is difficult to assess. Only one small nodule was found intraoperatively in the abdominal cavity and was submitted to pathology, but the diagnosis was scar tissue, and no WLPS component was detected in the resection specimen. Therefore, although the possibility of DLPS is low in this case, careful follow-up will continue because this condition is rare, and no firm treatment guidelines have been established.
This is the first case of SCS occurring in the anastomosis reported in the literature; however, in general, the frequent recurrence of undifferentiated soft tissue sarcoma is problematic. In our patient, the tumor did not show distant metastasis and could be completely resected surgically despite undifferentiated sarcomas metastasizing early. Once distant metastases develop, they cannot be radically removed by surgery, and the prognosis is very poor. The overall 2-year survival rate for anaplastic sarcoma has been reported to be approximately 60%. The generally short follow-up period for patients with anaplastic sarcoma, with some patients missing follow-up data and no reports of survival rates beyond 5 years in the literature, indicates that the overall prognosis for patients with anaplastic pleomorphic sarcoma of the anastomosis may be even worse.6 Local recurrence is also common in soft-tissue sarcomas, and Sawamura and Daigeler reported postoperative local recurrence within a median period of 19 and 15.7 months, respectively.10,11 Thus, frequent follow-up is recommended after sarcoma resection, especially during the first 2 years.12 Although complete surgical resection is the gold standard treatment, there are no fixed standards for lymph node dissection, partly because of the lack of reports. In the present case, although the lymph node dissection was limited because it had already been dissected in a previous surgery, complete resection was achieved grossly and on imaging, and a good prognosis was expected. Adjuvant radiation therapy and chemotherapy may be attempted postoperatively, depending on the patient’s condition and intraoperative status; however, further research is needed to select a specific regimen because of individual differences in efficacy. Adriamycin and ifosfamide should be considered for the treatment of soft tissue sarcomas if recurrence is suspected; however, SCS of gastrointestinal origin is extremely rare, and there is no clear evidence. Further molecular biological studies of SCS may provide the basis for molecularly targeted therapies and immunotherapy and offer hope for improving the prognosis of patients with SCS.