Supplementary Material for: Aggressive fibromatosis of the left Mesocolon mimicking a gastrointestinal stromal tumor: A ase report

Mesenteric Fibromatosis [MF] is a proliferative fibroblastic lesion of the intestinal mesentery. It constitutes 8% of all desmoid tumors, representing 0.03% of all neoplasms. It is benign histologically, although it could infiltrate locally and recur following excision; however, it is free from the potential to metastasize. It is spontaneous or associated with Familial Adenomatous Polyposis Mutation [FAP] as a part of Gardner's syndrome. This case report discusses the radiological, intraoperative, and histopathological findings from a 45-year-old male patient who presented with abdominal pain and a palpable mass in the left hemiabdomen. The pain was dull and aching, extending to the back and unrelated to any other gastrointestinal symptoms. There was no history of severe weight reduction. Furthermore, he is not a smoker. There were no comorbidities, severe medical diseases, or prior surgical procedures. Computerized tomography revealed a well-defined, lobulated, heterogeneously enhancing altered signal intensity mass at the mesocolon. Ultrasonography of the abdomen showed an intra-abdominal mass. Macroscopic mass characteristics include a well-defined mass measuring 22X14X11cm connected to a small intestine segment measuring 21x2x2cm. Histopathological and immunohistochemical examinations of the resected tumor, including positive nuclear immunostaining for beta-catenin, confirmed a postoperative diagnosis of desmoid-type fibromatosis. Based on its clinical presentation and computed tomography results, this case demonstrated how desmoid-type fibromatosis of the colon might mimic gastrointestinal stromal tumors [GIST]. Due to the varied therapies and follow-up methods used for these lesions, the differential diagnosis between desmoid type fibromatosis and GIST is clinically significant.

肠系膜纤维瘤病（Mesenteric Fibromatosis, MF）是一类发生于肠肠系膜的增殖性成纤维细胞病变。其在所有硬纤维瘤中占比8%，在全部肿瘤中占比0.03%。该病变组织学上为良性，虽可局部浸润并在切除术后复发，但无转移潜能。其发病可呈自发性，亦可作为加德纳综合征的组成部分，与家族性腺瘤性息肉病突变（Familial Adenomatous Polyposis Mutation, FAP）相关联。本病例报告详细阐述了1例45岁男性患者的影像学、术中及组织病理学表现。该患者因腹痛及左半腹部可触及肿块就诊，疼痛为钝性酸痛，可放射至背部，无其他胃肠道相关症状，无显著体重减轻病史，无吸烟史，亦无合并症、严重内科疾病或既往手术史。计算机断层扫描显示结肠系膜处存在一边界清晰、分叶状、不均匀强化的信号异常肿块；腹部超声检查提示腹腔内存在肿块。大体标本特征显示，有一大小为22×14×11cm的边界清晰肿块，与一段尺寸为21×2×2cm的小肠段相连。对切除的肿瘤开展组织病理学与免疫组织化学检查，结果显示β-连环蛋白的核免疫染色呈阳性，据此术后确诊为硬纤维瘤型纤维瘤病。结合患者的临床表现与计算机断层扫描结果，本例证实结肠硬纤维瘤型纤维瘤病可表现出与胃肠道间质瘤（Gastrointestinal Stromal Tumors, GIST）相似的临床特征。由于两类病变的治疗方案与随访策略存在差异，硬纤维瘤型纤维瘤病与GIST之间的鉴别诊断具有重要的临床价值。