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.