Differential diagnosis, investigations, and treatment
The primary lesion was not identified on various examinations, but the
lesion resolved spontaneously after approximately 6 months of follow-up.
In February 2023, the patient was referred to our hospital for
progressive anemia. A circumferential type 2 tumor was found at the
anastomosis after resection of the ascending colon by colonoscopy, which
was not found in July 2022 (Figure 2). The circumferential type 2 tumor
was located at the ascending colon, and a biopsy revealed a malignant
spindle tumor and the patient was referred to our department. Blood
tests showed no elevation of tumor markers, and other tests were normal.
Computed tomography revealed irregular wall thickening of 25 mm in the
ascending colon and a 37-mm tumor in the mesentery of the small
intestine, but no other obvious lesions (Figure 3). Magnetic resonance
imaging showed a pale high signal on T2-weighted and diffusion-weighted
images and a high signal on fat-suppressed T1-weighted images,
suggesting mucus accumulation (Figure 4).
The patient was diagnosed with a malignant spindle cell tumor localized
at the anastomosis. In March 2023, the patient underwent an open right
hemicolectomy of the colon and limited lymph node dissection (because
the lymph nodes had already been dissected in the previous surgery).
Only one small nodule was found intraoperatively in the abdominal
cavity. The nodule was submitted for pathological examination and
diagnosed as scar tissue. The operative time was 252 min, with a blood
loss of 120 mL. The patient was discharged on day 8 without any
postoperative complications. Macroscopically, the anastomosis around the
ascending colon, which was the primary site, revealed a circumferential
84×52 mm type 3 tumor with superficial necrotic tissue. The necrotic
tissue adhered to the superficial layer (Figure 5A). Histologically, the
tumor was greyish-white, dense, and situated in the intrinsic muscularis
propria, with atypical spindle-shaped cells in the tumor area,
infiltrating the subplasma membrane and showing atypical nuclear fission
(Figure 5B). The colon serosa was filled with fibrous hyperplasia,
vessel hyperplasia, inflammatory cell infiltration, and necrotic
tissues. Further immunohistochemical analysis showed that the tumor
cells positively stained for α1-antichymotrypsin (Figure 5C) and
vimentin (Figure 5D), were S-100- and HMB-45-negative, and were
MDM2-/CDK4-positive. Thus, the possibility of dedifferentiated
liposarcoma could not be denied, and the pathological examination
revealed an undifferentiated SCS centered on the anastomosis.