Multifocal Mesenteric Desmoid-Type Fibromatosis After Liver Transplantation: A Case Report

Introduction

Fibromatosis refers to a group of locally invasive tumors arising from fibroblasts or myofibroblasts, with biological behavior intermediate between benign and malignant tumors [1]. These can be classified into superficial and deep fibromatoses. Mesenteric desmoid fibromatosis (MDF), a subtype of deep fibromatosis, is relatively rare, preferentially involving sites such as the mesentery and retroperitoneum. Characterized by local invasiveness without metastatic potential but with a tendency for recurrence, MDF can cause compression or invasion of adjacent tissues and organs, leading to corresponding clinical symptoms [2].

The pathogenesis of MDF remains incompletely elucidated, potentially associated with multiple factors including genetic predisposition, hormonal influences, trauma, inflammation, and local tissue hypoxia. The diagnosis of MDF relies on specific detection methods such as β-catenin immunohistochemistry [3]. Liver transplant recipients require long-term immunosuppressive therapy to prevent allograft rejection, and this immunosuppressed state can modulate the immune system, including influencing tumorigenesis and progression [4]. However, mesenteric desmoid fibromatosis developing after organ transplantation is extremely uncommon, with only a few case reports documented in the Chinese and international literature [5,6]. Liver transplant recipients require long-term immunosuppressive therapy to maintain graft survival, and this state can significantly affect the biological behavior of MDF: immunosuppression can enhance the proliferative activity and invasiveness of the tumor, while increasing the difficulty of treatment. Surgical intervention can pose additional risks to the blood flow or function of the transplanted liver. All these present unique challenges for clinical decision-making. At present, the specific mechanisms underlying post-liver transplant MDF and its relationship to immunosuppression remain undefined [7].

This report describes a 46-year-old woman who, during follow-up after liver transplantation, was found to have a hypoechoic mass between intestinal loops in the mid-abdomen. Surgical resection and subsequent histopathological analysis confirmed the diagnosis of mesenteric desmoid fibromatosis with reactive mesenteric lymph node hyperplasia, involving intestinal segments II and III. Owing to the rarity of mesenteric desmoid fibromatosis in the post-liver transplant setting, there is a scarcity of clinical data and therapeutic experience. Therefore, the long-term follow-up of this case is of great significance for the clinical management of post-transplant patients. By presenting this case, we aim to enhance clinicians’ awareness of fibromatosis in unusual locations after liver transplantation, providing valuable insights for the diagnosis, management, and prognostic assessment of such conditions.

Case Report

A 46-year-old female patient underwent liver transplantation due to primary biliary cholangitis. More than 5 months after the operation, she was admitted to the hospital with renal insufficiency caused by refractory ascites, received splenic artery embolization, and underwent regular monitoring. Two years later, during a routine follow-up abdominal ultrasound examination, an ill-defined hypoechoic inter-intestinal mass was found in the mid-abdomen. During this period, the patient received regular treatment and reexaminations, without obvious discomfort or symptoms.

Abdominal ultrasound revealed a hypoechoic mass measuring approximately 5.8×4.3×3.3 cm within the right inter-intestinal space. The lesion had relatively well-defined borders and regular morphology, with detectable vascular flow signals both internally and peripherally (Figure 1).

A non-contrast abdominal computed tomography (CT) scan demonstrated a patchy soft tissue density lesion at the root of the left mesentery. Post-contrast imaging revealed mild heterogeneous enhancement of the lesion. Additionally, non-contrast CT identified a well-demarcated soft tissue mass, of tissue density (34 HU), measuring 5.5×3.6 cm, within the mesenteric fat space in the lower abdomen. Contrast-enhanced CT showed mild heterogeneous enhancement of the mass, with arterial and venous phase tissue density measuring 49 HU and 43 HU, respectively (Figure 2).

A left paramedian abdominal incision was made, followed by layered dissection to access the peritoneal cavity. Upon systematic abdominal exploration, a mesenteric mass measuring approximately 5 cm in diameter was identified approximately 80 cm distal to the ligament of Treitz. The mass demonstrated intimate adherence to the small intestinal wall, with localized bowel adhesions encasing the lesion while maintaining intestinal wall integrity (Figure 3). Additionally, 3 smaller mesenteric nodules (each ~1 cm in diameter) were visualized within the small bowel mesentery. Palpation revealed suspicious hyperplastic lymph nodes at 2 mesenteric sites. The procedure was completed without intraoperative complications, and the patient exhibited no immediate postoperative discomfort.

Gross examination revealed no distinct masses in intestinal segment I. Within intestinal segment II, a grayish-white mesenteric mass measuring approximately 6.8×3.5×5.5 cm was identified, which had been clinically incised with partial disruption of architectural integrity. Intestinal segment III demonstrated 3 nodules measuring 1.5×1.2×1.0 cm, 2.7×2.0×2.5 cm, and 2.0×1.8×1.3 cm, respectively. Additionally, 2 palpable lymph nodes (diameter 0.4 to 0.6 cm) were detected within the mesentery of intestinal segment III.

Histopathological examination of the mesenteric mass in intestinal segment II revealed a proliferation of spindle-shaped cells. No pathological abnormalities were identified in intestinal segment I or other bowel wall tissues. The 2 lymph nodes exhibited reactive lymphoid hyperplasia. Immunohistochemical analysis demonstrated negative staining for CD117, CD34, Desmin, and S100. Ki-67 staining indicated a low mitotic index (<2%). Notably, positivity for the nuclear accumulation of β-catenin was observed (Figure 4). Gastrointestinal stromal tumor (GIST) is typically characterized by positive expression of CD117, while leiomyosarcoma is typically featured by positive expression of desmin. In contrast, MDF often shows nuclear positivity for β-catenin and does not express the above-mentioned specific markers of GIST and leiomyosarcoma. The diagnosis of desmoid-type fibromatosis (DTF) is jointly confirmed through the differences in the expression profiles of these markers.

A follow-up non-contrast abdominopelvic CT scan performed 6 months postoperatively revealed no evidence of tumor recurrence, demonstrated no significant postoperative structural alterations in the mesenteric region, and showed no signs of abdominal metastasis.

Discussion

Desmoid fibromatosis (DF) is a rare borderline mesenchymal neoplasm characterized by locally aggressive growth without metastatic potential. With an incidence of 2 to 4 per million, intra-abdominal DF accounts for only 8% to 15% of all cases and predominantly involves the mesentery [2,8]. In this case, a 46-year-old woman, identified during post-liver transplantation surveillance with a hypoechoic inter-intestinal mass in the mid-abdomen, demonstrated multifocal mesenteric lesions (involving intestinal segments II and III) on imaging and surgical exploration. The uniqueness of this case lies in its occurrence in a post-liver transplantation patient. Currently, there are extremely few reports on mesenteric DF following liver transplantation in the Chinese and international literature. Moreover, this case presented as multifocal lesions, which differs from the typical manifestation of mesenteric DF, being mostly unifocal, as described in the literature [9,10]. Our report provides a new perspective for understanding the biological behavior of DF under special immune conditions.

The diagnostic process of this case highlights the synergistic effect between imaging and pathological analysis. In this patient, abdominal ultrasound and CT revealed a well-circumscribed hypoechoic mass with mild heterogeneous enhancement, aligning with reported imaging hallmarks of mesenteric DF (eg, “band-like” hypointensity, absence of necrosis or hemorrhage) [8]. Definitive diagnosis relied on histopathological and immunohistochemical analysis: microscopic examination showed spindle-shaped cell proliferation with collagen deposition, while immunohistochemistry demonstrated nuclear β-catenin accumulation (Figure 4) and negativity for CD117, CD34, desmin, and S100, effectively excluding GIST (CD117/CD34-positive) and leiomyosarcoma (myogenic marker-positive) [11]. Although catenin beta 1 (CTNNB1) or adenomatous polyposis coli (APC) mutation testing was not performed, β-catenin nuclear positivity indicated aberrant Wnt pathway activation, supporting a diagnosis of sporadic DF [12].

Current management of mesenteric DF emphasizes individualized strategies, balancing surgical resection, observation, and medical therapy. Complete surgical excision (R0 resection) was historically preferred, yet postoperative recurrence rates remain high (20–40%), particularly in multifocal cases (eg, involvement of segments II and III), which may predict greater recurrence risk [13].

The decision to perform surgical resection in this case was based on 3 key factors. First, the maximum diameter of the tumor reached 6.8 cm, and it involved the intestinal segments multifocally, posing a potential risk of intestinal obstruction, which is consistent with the consensus in the literature that “active intervention is required for tumors >5 cm” [14]. Second, the patient was a post-liver transplant recipient on long-term immunosuppressive therapy. Existing studies suggest that immunosuppression may enhance the proliferative activity of DF, and active surveillance under immunosuppressive conditions may be at risk of rapid tumor progression [15]. Third, the interaction between drug therapies (such as non-steroidal anti-inflammatory drugs and tyrosine kinase inhibitors) and immunosuppressants can increase the risk of hepatotoxicity to the transplanted liver, thus making surgery a safer option [16]. The short-term outcome of no recurrence at 6 months postoperatively also validates the rationality of this decision in this case.

DF exhibits significant biological heterogeneity, and cases with multifocality or involvement of the mesenteric root generally have a poor prognosis [17]. The present case featured both multifocality and a tumor size exceeding 5 cm, which are adverse prognostic factors, along with the special background of post-liver transplantation immunosuppression. Although the tumor in this case did not show rapid progression, differing from the conclusion in some reports that “immunosuppression may accelerate the progression of DF” [14], the long-term recurrence risk still warrants vigilance. Considering the characteristic of DF recurrence, which mostly occurs within 2 to 3 years after surgery as indicated in the literature, we used a monitoring protocol of abdominopelvic CT examination every 6 to 12 months for the patient. Meanwhile, we recommend supplementary CTNNB1/APC gene mutation detection (not yet performed in this case), as it may further indicate the recurrence risk (eg, CTNNB1 T41A mutation) [16]. In addition, despite the absence of symptoms related to familial adenomatous polyposis (FAP) in the patient, colonoscopy and APC gene detection are still necessary to rule out potential associations.

This case achieved accurate diagnosis and treatment of rare post-liver transplantation multifocal mesenteric DF through multidisciplinary collaboration (radiology, surgery, and pathology). Its core values are as follows: first, it supplements the clinical data of DF under the special immune state of liver transplantation, providing an example for understanding the association between immunosuppression and the biological behavior of DF; second, it verifies the value of β-catenin immunohistochemistry in differential diagnosis of complex cases; third, it offers a reference paradigm of “integrating transplantation background, tumor characteristics, and individualized risks” for treatment decision-making in similar patients. Future research can further focus on the application of Wnt/β-catenin pathway-targeted therapy in aggressive DF to improve the prognosis of special populations.

Conclusions

This case systematically excluded differential diagnoses, including GIST and leiomyosarcoma, through histopathological and immunohistochemical analyses, thereby underscoring the pivotal role of comprehensive histopathological assessment in the DTF. This provides a new perspective for clinicians in disease diagnosis.