[A Case of Desmoid-Type Fibromatosis of the Mesentery of Small Intestine].

Desmoid-type fibromatosis is a relatively rare disease, often associated with familial adenomatous polyposis and a history of abdominal surgery. A 43-year-old male patient presented with abdominal pain and contrast-enhanced CT showed a mass in the lower abdomen. The mass was a 4×4×3 cm white, dense tumor with a wreath-like arrangement of eosinophilic spindle-shaped cells. Immunostaining showed KIT(-), CD34(-), desmin(-), ß-catenin(+), SMA(few+), and the diagnosis was desmoid-type fibrosis. Six months after surgery, there was no apparent recurrence.

Correlation Between the Severity of Adhesions and Desmoid Disease in Patients With Familial Adenomatous Polyposis: A Prospective Cohort Study.

BACKGROUND: Clinical experience teaches that intraperitoneal adhesions are more severe in patients with familial adenomatous polyposis than in patients without it. This impression may come from the common association of familial adenomatous polyposis with desmoid disease. OBJECTIVES: This study aimed to determine whether patients with familial adenomatous polyposis and desmoid disease develop more severe adhesions than those without desmoid disease. DESIGN: Prospectively collected data study. SETTINGS: Hereditary colorectal cancer center in a tertiary referral hospital. PATIENTS: Patients undergoing first reoperative intra-abdominal surgery for familial adenomatous polyposis; controls were those having their initial abdominal surgery. INTERVENTIONS: Surgery and adhesiolysis. MAIN OUTCOME MEASURES: Presence and type of desmoid disease; presence and severity of nondesmoid intraperitoneal adhesions. Where patients had multiple operations, only the first reoperative surgery was chosen. Desmoid disease was noted as reaction (sheet) or mass. Adhesions were graded as none, mild (<10 min for mobilization), average (10-30 min), and severe (>30 min or significant bowel damage). Patients having their first abdominal surgery for familial adenomatous polyposis were used as a control group. RESULTS: A total of 211 patients had no prior surgery; 5% had desmoids and 1% had adhesions. One hundred thirty-seven patients underwent reoperative surgery: 39% had desmoid disease ( p < 0.05 vs no prior surgery), the highest rate being in patients after IPAA (57%), and 45% had severe adhesions ( p < 0.01 vs no prior surgery), worst after Koch pouch (89%), and total proctocolectomy with ileostomy (82%). Thirty-six percent of patients without desmoid disease had severe adhesions. Desmoid reaction was associated with severe adhesions in 47% of cases and desmoid tumors in 66% of cases. LIMITATIONS: Possible limitations include the potential overlap between desmoid adhesions and nondesmoid adhesions and the potential for inaccuracy in defining the time of adhesiolyses. CONCLUSIONS: Familial adenomatous polyposis is associated with severe postoperative adhesions after reoperative abdominal surgery, especially in patients who develop desmoid disease. See Video Abstract . CORRELACIN ENTRE LA GRAVEDAD DE LAS ADHERENCIAS Y LA ENFERMEDAD DESMOIDEA EN PACIENTES CON POLIPOSIS ADENOMATOSA FAMILIAR ESTUDIO PROSPECTIVO DE COHORTES: ANTECEDENTES:La experiencia clínica demuestra que las adherencias intraperitoneales son más graves en pacientes con poliposis adenomatosa familiar que en pacientes sin enfermedad desmoidea. Esta impresión puede provenir de la asociación común de poliposis adenomatosa familiar con enfermedad desmoidea.OBJETIVOS:Ver si los pacientes con poliposis adenomatosa familiar y enfermedad desmoidea desarrollan adherencias más graves que aquellos sin enfermedad desmoidea.DISEÑO:Estudio de datos recolectados prospectivamente.AJUSTES:Centro de cáncer colorrectal hereditario en un hospital de referencia terciario.PACIENTES:Pacientes sometidos a una primera cirugía intraabdominal de caracter reoperatorio por poliposis adenomatosa familiar: los controles fueron los que se sometieron a su cirugía abdominal inicial.INTERVENCIONES:Cirugía y adhesiolisis.PRINCIPALES MEDIDAS DE RESULTADO:Presencia y tipo de enfermedad desmoidea; presencia y severidad de adherencias intraperitoneales no desmoideas. Cuando los pacientes tenían múltiples operaciones, solo se eligió la primera cirugía reoperatoria. La enfermedad desmoidea se anotó como reacción (hoja filamentosa) o masa. Las adherencias se calificaron como ninguna, leve (<10 minutos para la movilización), promedio (10 a 30 minutos) y severa (>30 minutos o daño intestinal significativo). Los pacientes sometidos a una primera cirugía abdominal por poliposis adenomatosa familiar se utilizaron como grupo de control.RESULTADOS:211 pacientes no tenían cirugía previa: 5% desmoideos y 1% adherencias. 137 pacientes se sometieron a cirugía reoperatoria: 39% tenía enfermedad desmoidea ( p < 0,05 frente aquellos sin cirugía previa), la tasa más alta se presentó en aquellos pacientes después de una anastomosis ileoanal con reservorio (57%) donde el 45% tenía adherencias graves ( p < 0,01 frente aquellos sin cirugía previa), peores resultados se observaron después de la confección de un reservorio de Koch (89%) y luego de proctocolectomía total con ileostomía (82%). El 36% de los pacientes sin enfermedad desmoidea tenían adherencias graves. La reacción desmoidea se asoció con adherencias graves en el 47% de los casos, y los tumores desmoides se asociaron con adherencias graves en el 66% de los casos.LIMITACIONES:Superposición potencial entre adherencias desmoideas y adherencias no desmoideas. Posible inexactitud en la definición del tiempo de adhesiolisis.CONCLUSIONES:La poliposis adenomatosa familiar se asocia con adherencias postoperatorias graves después de una cirugía abdominal reoperatoria, especialmente en pacientes que desarrollan enfermedad desmoidea. (Traducción-Dr. Xavier Delgadillo ).

Surgical techniques and effectiveness of laparoscopic resection of abdominal wall desmoid-type fibromatosis and defect reconstruction: a single-center retrospective analysis.

PURPOSE: Although the treatment of abdominal wall desmoid-type fibromatosis (DF) has evolved over the past decades, surgical treatment remains an important approach. Previously, surgeries for abdominal DF were mostly performed by laparotomy, which involves massive dissection and significant trauma. Here, we report our single-center experience of the laparoscopic management of abdominal wall DF in young female patients. METHODS: The clinical data of nine patients diagnosed with abdominal wall DF during January 2020-April 2022 at the Qilu Hospital of Shandong University were retrospectively analyzed. All patients underwent laparoscopic resection of abdominal wall DF and immediate abdominal wall reconstruction (AWR) with mesh augmentation via the intraperitoneal onlay mesh (IPOM) technique. RESULTS: Laparoscopic DF resection and AWR were successfully performed in all patients. The mean operation time was 175.56 ± 46.20 min. The width of abdominal wall defect was 8.61 ± 3.30 cm. Full- and partial-thickness myofascial closure and reapproximation were performed in five, two, and two patients, respectively. The average mesh size was 253.33 ± 71.01 cm2. The total and postoperative lengths of hospital stay were 11.00 ± 3.46 and 4.89 ± 2.03 days, respectively. Tumor recurred in one patient after 20 months of the resection. Nonetheless, death, herniation, or bulging were not observed in any patient during a mean follow-up of 16.11 ± 8.43 months. CONCLUSION: Laparoscopic resection of abdominal wall DF and immediate AWR with IPOM mesh reinforcement is safe and reliable for young female patients. Management of such patients should be decided according to the biological behavior, size, and location of tumors.

Risk factors for local recurrence of upper extremity desmoid tumors.

INTRODUCTION: Upper extremity (UE) desmoid tumors are locally aggressive neoplasms with high recurrence rates. Our study sought to analyze the demographics and treatment strategies of UE desmoid tumors and identify risk factors for recurrence. MATERIALS AND METHODS: A retrospective review of 52 patients with histologically confirmed UE desmoid tumors treated at our institution between 1990 and 2015 was conducted. Survival was assessed using the Kaplan-Meier method and the Cox proportional hazards model was used for risk factor analysis. RESULTS: For the entire cohort, median age was 40 (29-47) years, 75% were female, and 48% had local recurrence. The median tumor size was 45 (15-111) cm3 on imaging. Twenty-two patients had a previous resection. The most common treatments were surgery alone (50%) and surgery with adjuvant radiotherapy (21%). Tumor size ≥5 cm and tumor volume ≥40 cm3 on imaging were associated with increased recurrence (p = 0.006 and p = 0.005, respectively). Age and sex were not associated with local recurrence. Patients with a tumor size ≥5 cm were 2.6 times more likely to present with recurrence. At the 10-year mark, a lower local recurrence-free survival was seen in patients with tumors ≥5 cm (72.2% vs. 36.3%, p = 0.042) or ≥40 cm3 (67.2% vs. 32.7%, p = 0.034). CONCLUSION: In our study, only tumor dimensions appeared to modify recurrence risk.

MRI-based navigated cryosurgery of extra-abdominal desmoid tumors using skin fiducial markers: a case series of 15 cases.

BACKGROUND: Precision surgery is becoming increasingly important in the field of Orthopaedic Oncology. Image-guided percutaneous cryosurgery (CRA) has emerged as a valid treatment modality for extra-abdominal desmoid tumors (EDTs). To date, most CRA procedures use CT-based guidance which fails to properly characterize tumor segments. Computer-guided MRI navigation can address this issue however, the lack of a fixed landmark for registration remains a challenge. Successful CRA correlates directly with precision approaches facilitated by intraoperative imaging guidance. This is the first study that attempts to assess the feasibility and efficacy of a novel approach of using skin fiducial markers to overcome the challenge of a MRI-based navigation CRA for symptomatic or progressive EDTs. METHODS: In this retrospective study conducted between 2018 and 2020, 11 patients at a single center with symptomatic or progressive EDTs were treated with CRA using intraoperative MRI navigation. Fifteen cryosurgery procedures were performed, each adhering to a personalized pre-operative plan. Total tumor size, viable and non-viable portions pre- and post-operation, and SF-36 questionnaire evaluating subjective health were recorded. RESULTS: All CRAs demonstrated 100% adherence to the predetermined plan. Overall, tumor size decreased Median= -56.9% [-25.6, -72.4]) with a reduction in viable tissue, (Median= -80.4% [-53.3, -95.2]). Four patients required additional CRAs. Only one patient's tumor did not reduce in size. One patient suffered from local muscle necrosis. Pre-operation, the average physical and mental scores 41.6 [29.4, 43] and 26.3 [17.6, 40.9] respectively. Post-operation, the average physical and mental scores were 53.4[38, 59.7] and 38 [31.2, 52.7] respectively. CONCLUSION: These findings provide an early indication of the feasibility and efficacy of performing percutaneous cryosurgery using skin fiducial marker registration for MRI-computed navigation to treat EDTs safely. Larger cohorts and multicenter evaluations are needed to determine the efficacy of this technique.

[A Case of Desmoid Fibromatosis of the Small Intestinal Mesentery Institutions].

The patient was a 27-year-old man. He was referred to our hospital because he was aware of a mass in his abdomen. An abdominal ultrasound showed a 70-mm mass lesion. Enhanced computed tomography showed a 70-mm mass with well- defined margins and heterogeneous internal enhancement near the proximal jejunum. The patient was diagnosed with a suspected primary submucosal tumor of the duodenum or small intestine, and surgery was planned to diagnose and treat the tumor. The tumor was located in the upper jejunal mesentery, and tumor resection and partial small bowel resection were performed. Histopathological examination revealed proliferation of spindle-shaped cells without karyomitosis, and mixed collagen fibers in the tissue. Immunohistochemistry showed ß-catenin(+), SMA(+), AE1/AE3(-), KIT(-), CD34(-), and S-100(-). Based on these findings, we diagnosed primary desmoid fibromatosis of the small intestinal mesentery. In this report, we describe a case of primary desmoid fibromatosis of the small intestinal mesentery with a review of the literature.

Unusual Presentation of an Uncommon Malignancy: A 74-Year-Old Woman with Aggressive Fibromatosis of the Large Intestine Presenting as a Liver Mass and the Therapeutic Management.

BACKGROUND Desmoid tumors are a fibroblastic proliferation of soft tissues, with an extreme inclination for local dissemination and recurrence. Surgical excision is the usual treatment choice, with data regarding pharmaceutical treatment being scarce. CASE REPORT A 74-year-old female patient was admitted to "Laikon" General Hospital of Athens, Greece presenting with acute kidney injury secondary to diarrhea. The ultrasound, CT, and abdominal MRI performed showed a 12×6×10 cm tumorous liver lesion. Biopsy of the lesion revealed loosely organized, mesenchymal tissue with spindle cells, and myxoid stroma. Immunochemistry was positive for SMA and b-catenin. Right hemicolectomy was performed with tumor-free surgical margins (R0 resection) and tamoxifen was initiated. Six months after the last MRI (3 months after the use of tamoxifen), a follow-up MRI was performed. The tumor had increased to 14.2×11×12.3 cm, and at the next follow-up it had grown to 20.3×19 cm maximal dimensions; no new metastases were found. The patient received sorafenib and pazopanib. Our patient had PFS with sorafenib for more than 2 years and remained in a good performance status (ECOG 1). For Pazopanid, the median PFS for this treatment option was 6.5 months. CONCLUSIONS The results were good and show a promising method for the treatment of this rare but severe malignancy.

Desmoid fibroma simulating malignant breast neoplasm: A case report and literature review.

INTRODUCTION: Desmoid fibroma (DF) is a disorder characterized by strong clonal proliferation of myofibroblasts and fibroblasts. We describe a case of DF that mimicked a breast tumor, along with a review of the literature on the clinical manifestation, diagnostic process, and course of therapy for this combative disease. CASE REPORT: A 34-year-old female patient with breast lump at the junction of the upper quadrants of the left breast. After the diagnosis of DF, it was decided to perform a sectorectomy of the left breast associated with post-quadrant reconstruction, with immunohistochemistry and findings compatible with DF. DISCUSSION: Clinically manifests as a solid mass that is often painless and occasionally adherent to the chest wall. A treatment strategy should be idealized for each patient. Thus, there is the possibility of performing radical surgery for resection and/or radiotherapy, and surgery may be followed by radiotherapy.

Papillary thyroid carcinoma with desmoid fibromatosis: a case report and review of literature.

Desmoid-type fibromatosis (DF) is a rare monoclonal, fibroblastic proliferation characterized by an unpredictable and variable clinical course. We present the case of a 56-year-old woman who underwent total thyroidectomy for papillary thyroid carcinoma in 2012 and who developed a cervical mass at the left laterocervical level during follow-up, raising the diagnosis of tumor recurrence. Computed tomography of the neck showed solid formations with heterogeneous contrast uptake in the right lateral region of the neck. At the level of the thoracic operculum, a second 26-mm formation was observed that medially contacted the left lateral wall of the trachea. Lateral lymphadenectomy was performed, which was incomplete. Histology showed findings consistent with desmoid-type fibromatosis. DF are slowly proliferating, non-metastatic tumors with a highly invasive capacity that are usually present in familial adenomatous polyposis (FAP)-Gardner syndrome. Our case had a history of massive colonic polyposis and first-degree relatives of colorectal cancer.

La fibromatosis de tipo desmoide (FD) es una rara proliferación fibroblástica monoclonal caracterizada por un curso clínico impredecible y variable. Presentamos el caso de una mujer de 56 años intervenida de tiroidectomía total por carcinoma papilar de tiroides en 2012 y que durante el seguimiento desarrolla una masa cervical a nivel laterocervical izquierdo, planteando el diagnóstico de recidiva tumoral. La tomografía computarizada de cuello demostró formaciones sólidas con captación heterogénea de contraste en la región lateral derecha del cuello. A nivel del opérculo torácico se observó una segunda formación de 26 mm que contactaba medialmente con la pared lateral izquierda de la tráquea. Se realizó una linfadenectomía lateral, que resultó incompleta. La histología mostró hallazgos compatibles con FD. La FD son tumores de proliferación lenta, no metastásicos y con una capacidad altamente invasiva que suelen estar presentes en la poliposis adenomatosa familiar (PAF)-síndrome de Gardner. Nuestro caso tenía antecedentes de poliposis colónica masiva y familiares de primer grado de cáncer colorrectal.

CTNNB1 and APC Mutations in Sinonasal Myxoma : Expanding the Spectrum of Tumors Driven By WNT/ß-catenin Pathway.

Sinonasal myxoma (SNM) is a rare, benign mesenchymal neoplasm with distinct clinicopathologic features and aberrant nuclear localization of ß-catenin by immunohistochemistry. The molecular underpinnings have been linked to that of a "myxoid variant" of desmoid fibromatosis. Herein, we describe a series of 8 cases of SNM and propose clinical and biologic differences compared with desmoid fibromatosis. Our patient cohort is comprised of 5 males and 3 females (age range: 10 mo to 12 y), 6 of whom are aged less than or equal to 24 months. All presented with facial swelling, reflecting lesions involving the maxillary bone, and all underwent resection. All tumors were variably cellular and comprised of bland spindled to stellate cells in a profusely myxoid background with diffuse nuclear ß-catenin expression. All cases of SNM were analyzed by next-generation sequencing using the Oncopanel assay. Three cases failed sequencing, 2 of 5 successful cases exhibited exon 3 CTNNB1 alterations involving the ubiquitin recognition motif, and 3 had adenomatous polyposis coli ( APC ) deletions. One patient had APC germline testing which was negative. No germline testing was available for the remaining 7 patients. Follow-up data over a range of 1 month to 23 years was available for 7 of the 8 SNMs. One case patient had local recurrence, and all were alive without evidence of disease. This is in contrast to the high recurrence rate typically seen in desmoid fibromatosis, particularly after resection. Our findings expand the spectrum of tumors with underlying WNT/ß-catenin pathway and highlight the histologic, clinical, and genetic differences of SNM compared with desmoid fibromatosis. APC deletion raises the possibility of underlying germline alteration and familial adenomatous polyposis.

Treatment of a Desmoid Tumor That Enlarged During Pregnancy: A Case Report and Literature Review.

Desmoid tumors are rare soft-tissue tumors that exhibit locoregional aggressiveness and a high local recurrence rate following initial resection. No fixed recommendations have been established with regard to the timing and method of treatment for desmoid tumors that enlarge during pregnancy. Desmoid tumors tend to enlarge during pregnancy, and most do not regress spontaneously postpartum. Thus, surgery may be required even during pregnancy. We report a case of an abdominal wall desmoid tumor that grew to 90 mm during pregnancy and was resected at 17 weeks of gestation. Marginal resection was performed, and the surgical margin was microscopically positive. The postoperative course and the pregnancy were uneventful, and no recurrence was observed at the 15-month follow-up visit.

Desmoid-type fibromatosis of the mesentery: a clinicopatho-logical and genetic analysis of 9 cases. / è‚ ç³»è†œéŸ§å¸¦æ ·çº¤ç»´ç˜¤ç— æ‚£è€ ä¸´åºŠç— ç†å­¦åˆ†æž.

Nine cases of mesenteric desmoid-type fibromatosis were diagnosed and treated in Taizhou Hospital, Wenzhou Medical University between January 2010 and May 2022, including 2 females and 7 males, aged 16 to 59 years. The lesions were in the mesentery of small intestine with 7 cases, ileocecal junction with 1 cases and transverse colon with 1 case. The tumors had an unclear boundary and no envelope, the section was solid, gray and tough. The mean maximum diameter was (10.7±8.5) cm (range 3.5-33.0 cm). Microscopically, fusiform fibroblasts and myofibroblasts were parallel, bunched or staggered, buried in a large amount of extracellular collagen. The cell morphology was relatively consistent, without obvious atypia, and mitosis was rare. Immunohistochemistry showed that the tumor cells were positive for vimentin (9/9), ß-catenin (9/9), while smooth muscle actin (5/9) stains were focally positive. Ki-67 proliferation index was 1%-10%. Cytokeratin Pan, S-100, STAT6, CD117, DOG1, CD34, desmin and anaplastic lymphoma kinase stains were negative. Genetic analysis showed that there were 7 cases of c.121G>A(p.Thr41Ala) mutation of CTNNB1 gene, 1 case of c.121G>A(p.Thr41Ala) and 1 case of c.134C>T(p.Ser45Phe) double mutation, and 1 case of wild type. Tumors were surgically resected in all 9 cases. Eight cases had no recurrence or metastasis, 1 case had recurrence 6 months later, and no recurrence or metastasis after additional surgical resection.

Desmoid tumours (extra-abdominal), a surgeon's nightmare.

Desmoid tumours are a rare fibroblastic proliferation of monoclonal origin, arising in deep soft-tissues. Histologically, they are characterized by locally aggressive behaviour and an inability to metastasize, and clinically by a heterogeneous and unpredictable course. Desmoid tumours can occur in any anatomical site, but commonly arise in the limbs. Despite their benign nature, they can be extremely disabling and sometimes life-threatening, causing severe pain and functional limitations. Their surgical management is complex and challenging, due to uncertainties surrounding the biological and clinical behaviour, rarity, and limited available literature. Resection has been the first-line approach for patients with a desmoid tumour but, during the last few decades, a shift towards a more conservative approach has occurred, with an initial 'wait and see' policy. Many medical and regional forms of treatment are also available for the management of this condition, and others have recently emerged with promising results. However, many areas of controversy remain, and further studies and global collaboration are needed to obtain prospective and randomized data, in order to develop an appropriate shared stepwise approach.

Prognostic Factors for Local Recurrence after Cryoablation of Desmoid Tumors.

PURPOSE: To determine the risk factors for local of adult patients treated for desmoid tumors by cryoablation. MATERIALS AND METHODS: Eighty-four patients treated for nonabdominopelvic desmoid tumors by cryoablation from July 2012 to July 2020 were included in a retrospective study. The population was composed of 64 women (76.19%) and 20 men (23.81%), aged from 16 to 75 years (median, 35 years ± 14.25). Each patient underwent preprocedural gadolinium-enhanced magnetic resonance imaging and was followed up to 36 months with the same technique. Clinical features, such as tumor size and previous treatment, epidemiological features, and the technical parameters of cryoablation, were studied. RESULTS: Local relapse was found in 19 (22.62%) of 84 patients. The 12-, 24-, and 36-month progression-free survival rates were 89% (95% confidence interval [CI], 79-94), 74% (95% CI, 60-83), and 68% (95% CI, 53-79), respectively. In univariate analysis, significant prognostic factors associated with local recurrence were non-abdominal wall location (P = .042), debulking strategy (P = .0105), risk of visceral injury (P = .034) or peripheral nerve injury during cryoablation (P = .033), previous radiation therapy (P = .043), and treatment before 2016 (P = .008). In multivariate analysis, abdominal wall tumors displayed the best outcome, whereas the neck and trunk showed a high rate of recurrence (hazard ratio, 7.307 [95% CI, 1.396-38.261]). CONCLUSIONS: The local recurrence of desmoid tumors after cryoablation depends on a number of prognostic factors, in particular, a non-abdominal wall location of the tumor and previous local treatment such as surgery or radiation therapy.

Disease and economic burden of surgery in desmoid tumors: a review.

INTRODUCTION: Desmoid tumors (DT) are soft-tissue tumors that infiltrate into surrounding structures with ill-defined margins. Although surgery is a potential treatment option, complete excision with negative margins is not often possible, the postsurgery recurrence rate is high, and surgery can result in disfigurement and/or loss of function. AREAS COVERED: We conducted a literature review to assess the burden of surgery in patients with DT, focusing on recurrence rates and functional deficits resulting from surgeries. Since economic data related to DT surgery is lacking, reviews of surgery costs in soft-tissue sarcomas and of general costs of amputations were conducted. Risk factors for DT recurrence after surgery are young age (<30 years), tumor location (extremities), tumor size (>5 cm in greatest diameter), positive resection margins, and history of trauma in the area of the primary tumor. Tumors in the extremities have the highest risk of recurrence (30%-90%). Lower rates of recurrences have been reported when radiotherapy was used after surgery (14%-38%). EXPERT OPINION: Although effective in specific cases, surgery may be associated with poor long-term functional outcomes and higher economic costs. Therefore, it is imperative to find alternative treatments with acceptable efficacy and safety profiles that do not adversely affect functional aspects in patients.

Does the Addition of Mutations of CTNNB1 S45F to Clinical Factors Allow Prediction of Local Recurrence in Patients With a Desmoid Tumor? A Local Recurrence Risk Model.

BACKGROUND: The initial approach to the treatment of desmoid tumors has changed from surgical resection to watchful waiting. However, surgery is still sometimes considered for some patients, and it is likely that a few patients would benefit from tumor removal if the likelihood of local recurrence could be predicted. However, to our knowledge, there is no tool that can provide guidance on this for clinicians at the point of care. QUESTION/PURPOSE: We sought to explore whether a combined molecular and clinical prognostic model for relapse in patients with desmoid tumors treated with surgery would allow us to identify patients who might do well with surgical excision. METHODS: This was a retrospective, single-center study of 107 patients with desmoid tumors who were surgically treated between January 1980 and December 2015, with a median follow-up of 106 months (range 7 to 337 months). We correlated clinical variables (age, tumor size, and localization) and CTNNB1 gene mutations with recurrence-free survival. Recurrence-free survival was estimated using a Kaplan-Meier curve. Univariate and multivariable analyses of time to local recurrence were performed using Cox regression models. A final nomogram model was constructed according to the final fitted Cox model. The predictive performance of the model was evaluated using measures of calibration and discrimination: calibration plot and the Harrell C-statistic, also known as the concordance index, in which values near 0.5 represent a random prediction and values near 1 represent the best model predictions. RESULTS: The multivariable analysis showed that S45F mutations (hazard ratio 5.25 [95% confidence interval 2.27 to 12.15]; p < 0.001) and tumor in the extremities (HR 3.15 [95% CI 1.35 to 7.33]; p = 0.008) were associated with a higher risk of local recurrence. Based on these risk factors, we created a model; we observed that patients considered to be at high risk of local recurrence as defined by having one or two factors associated with recurrence (extremity tumors and S45F mutation) had an HR of 8.4 compared with patients who had no such factors (95% CI 2.84 to 24.6; p < 0.001). From these data and based on the multivariable Cox models, we also developed a nomogram to estimate the individual risk of relapse after surgical resection. The model had a concordance index of 0.75, or moderate discrimination. CONCLUSION: CTNNB1 S45F mutations combined with other clinical variables are a potential prognostic biomarker associated with the risk of relapse in patients with desmoid tumors. The developed nomogram is simple to use and, if validated, could be incorporated into clinical practice to identify patients at high risk of relapse among patients opting for surgical excision and thus help clinicians and patients in decision-making. A large multicenter study is necessary to validate our model and explore its applicability. LEVEL OF EVIDENCE: Level III, therapeutic study.

Intra-abdominal desmoid fibromatosis mimicking tumour recurrence after the operation: A case series.

INTRODUCTION: Desmoid fibromatosis is a multifactorial disorder classified as a category of intermediate, locally aggressive behaviour, which might be associated with CTNNB1 or APC mutations, trauma, surgery, or pregnancy. CASE REPORTS: We present two cases of postoperative intra-abdominal desmoid fibromatosis. The first case occurred 14 months after the resection of a retroperitoneal gastrointestinal stromal tumour. The second case was located in the mesentery, as evidenced on an 18-month followup after a laparoscopy-assisted anterior resection for adenocarcinoma at the rectosigmoid junction. Under the clinical diagnosis of recurrence, tissue excisions were conducted. Microscopically, the tissue was composed of bland spindle cells without cytological atypia, admixed with collagen bundles. Both tumours exhibited nuclear expression of ß-catenin on immunohistochemical staining, which is a desirable criterion for desmoid fibromatosis. DISCUSSION: Although positron emission tomography aids the diagnosis of recurrence, the radiological features of desmoid fibromatosis in computed tomography or magnetic resonance images are nonspecific and preoperative diagnosis of desmoid fibromatosis is difficult. The histological diagnosis of desmoid fibromatosis is difficult, especially when the specimen is small. The histological differential diagnosis of desmoid fibromatosis includes other myofibroblastic or fibroblastic tumours or lesions. Additional studies, such as ß-catenin immunohistochemistry or CTNNB1 mutation analysis, can enable accurate diagnosis of desmoid fibromatosis. A correct diagnosis is essential, because the current therapeutic strategy is a "waitand- watch" approach, which is significantly different from those of the other locally aggressive, intermediate soft tissue neoplasms. We have summarised the clinicopathological, histological and immunohistochemical features of the post-operative desmoid fibromatosis.