Lower Rate of CTNNB1 Mutations and Higher Rate of APC Mutations in Desmoid Fibromatosis of the Breast: A Series of 134 Tumors

Desmoid fibromatosis (DF) is a rare, locally aggressive, nonmetastasizing fibroblastic/myofibroblastic tumor with a tendency to recur and an unpredictable clinical course. A “wait-and-see” policy is the new standard of care. DF are characterized by activating alterations of the wnt/Beta-catenin pathway: CTNNB1 or adenomatous polyposis coli gene (APC) mutations (these mutations being mutually exclusive). Desmoid-type fibromatosis of the breast (DFB) is rare with an incidence of 0.2% of breast tumors. The diagnosis of DFB is difficult, as it must be distinguished from metaplastic carcinoma and other spindle cell lesions. Sequencing of 128 DFB identified a lower rate of CTNNB1 mutations using Sanger (65.6%) or Sanger+next-generation sequencing (77.7%) and a higher rate of APC mutations (11.8%) than in all-site DF. By excluding patients with familial adenomatous polyposis (n=2), the rate of APC mutations in DFB was high (10.7%). The distribution of CTNNB1 mutations in DFB was different from all-site DF, with a higher rate of T41A (68.9%), a lower rate of S45F (5.7%), and a similar rate of S45T (12.6%). By combining the 2 molecular techniques in a 2-step manner (Sanger, then next-generation sequencing), we increased the detection rate of CTNNB1 mutations and lowered the rate of wild-type tumors from 34.4% to 9.8%, therefore improving the diagnosis of DFB. The identification of the exon 3 CTNNB1 mutation in breast spindle cell lesions is a highly specific tool for the diagnosis of DFB, in addition to extensive immunohistochemical analysis. Our study also underlines the importance of APC in DFB tumorigenesis. These findings have significant implications for patient care and management.

The mainstay of the treatment for desmoid-type fibromatoses has been shifting from surgery to drug treatment, making accurate prediction of the efficacy of drug treatment of extreme importance. On the other hand, desmoid-type fibromatoses arise everywhere in the body. The purpose of this systematic review was to address the clinical question of whether tumour location has an impact on the efficacy of drug treatment. A literature search from January 1990 to August 2017 was conducted. Four reviewers independently assessed and screened the literature for eligibility and determined the final articles. In total, 128 articles were extracted. After the screenings, 5 were chosen for the final evaluation. The drugs used in these articles were one each of toremifene, sorafenib, and methotrexate and vinblastine and of meloxicam. There were no randomized controlled trials, and two prospective and three retrospective case series were included. Therapeutic effects were observed slightly more markedly in extremity using meloxicam or methotrexate and vinblastine. In contrast, the efficacy of toremifene was slightly higher in non-extremity. However, the evidence level of all of the reports was judged to be low. Considering the low evidence level, we concluded that the site-specific therapeutic effects of drugs could not be confirmed in desmoid-type fibromatoses.

An accurate diagnosis is crucial to determine the treatment modality for desmoid-type fibromatosis, although the histopathological diagnosis is occasionally difficult to make. Many desmoid-type fibromatosis have been reported to have hotspot mutation of Beta-catenin gene (CTNNB1). In the present study, we performed a systematic review to verify the usefulness of CTNNB1 mutation analysis in the diagnosis of desmoid-type fibromatosis. A literature search from January 1990 to August 2017 was conducted. Three reviewers independently assessed and screened the literature for eligibility and determined the final articles to be evaluated. Data regarding the sensitivity, specificity, accuracy and usefulness of CTNNB1 mutation analysis in the diagnosis of desmoid-type fibromatosis were recorded. We rated each report according to the Grading of Recommendations Development and Evaluation approach. The search yielded 90 studies, seven of which were included after the first and second screenings. The positive rate of CTNNB1 mutation in desmoid-type fibromatosis was 86.8%, but the cohort of six of the seven reports was already diagnosed histopathologically as desmoid-type fibromatosis. Therefore, the usefulness of CTNNB1 mutation analysis in a cohort that is difficult to diagnose histopathologically is not clear in this review. Nevertheless, CTNNB1 mutation showed very high specificity in desmoid-type fibromatosis, indicating the usefulness of CTNNB1 mutation analysis in its diagnosis in combination with histological examination.

Gardner syndrome (GS) is a form of familial adenomatous polyposis (FAP) and is characterized by colonic polyposis, osteomas, and soft-tissue tumors. Desmoid tumors (DT) are lesions of mesenchymal origin and are an extra-colonic manifestation of GS. Gardner-associated fibroma (GAF) is considered to be a benign soft-tissue lesion related to DT and FAP. Here we present a case of an 18-year-old female patient with a huge lump in her right thoracic cavity and another lump located in her left lumbar muscles who was diagnosed with GS through a colonoscopy and through adenomatous polyposis coli (APC) gene mutation detection. The patient underwent a surgical resection of the right thoracic tumor. Three months later, the left waist lump underwent medical treatment with tamoxifen and celecoxib and was monitored using computed tomography (CT). Subsequently, colonoscopy screening was performed annually to prevent colorectal cancer. GAF is frequent in GS, and such a huge GAP in the thorax is very rare, with few cases reported in the literature. Patients with GS must be closely monitored, and clinical and imaging examinations must be performed to detect any signs of tumors.

This report presents a rare case of pancreatic desmoid fibromatosis in a 72 year old man, who on a follow-up CT for a previously diagnosed angiomyolipoma of the kidney was found to have a 4.0 cm pancreatic tail mass. This was sampled pre-operatively by endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA). Examination of the cytology material showed a low-grade spindle cell lesion. Immunohistochemistry (IHC) performed on FNA cell block showed the lesional cells to be positive for beta-catenin, consistent with fibromatosis. Additional mutational analysis on cell block material revealed the characteristic CTNNB1 gene mutation (T41A), confirming the diagnosis. The mass was then surgically resected and again confirmed to be desmoid fibromatosis on histopathologic examination. On review of previously published cases of pancreatic desmoid fibromatosis, most were initially suspected to be some type of pancreatic neoplasm and were not biopsied prior to surgical resection. This case suggests a potential key role for fine-needle aspiration cytology in the preoperative diagnosis of pancreatic and other intra-abdominal desmoid tumors, particularly as evidence emerges that non-surgical treatment may be a viable first option for some cases.

We analyzed 87 consecutive patients with histologically-proven sporadic primary DTF, first recurrence or residual disease managed at our institution between 2000 and 2018. Patients and tumor-related variables were reviewed and analyzed. Two different treatment strategies were adopted according to different time periods: in the “early period” (2000-2010) patients underwent surgical treatment irrespective of the clinical presentation, whereas in the “late period” (2012-2018) asymptomatic patients used to undergo a wait-and-see strategy. The event-free survival (EFS) was compared trough a pre-post comparison. In the early period, surgery was performed in 51 (94.4%) patients and watchful waiting in 3 (5.6%). In the late period, the watchful waiting group accounted for 24 (72.7%) patients and the surgical group for 9 (27.3%). No statistically independent prognostic factors were found. EFS did not show statistically significant differences between early and late period groups. Wait-and-see policy has shown to be equivalent to upfront surgery in terms of EFS; therefore, a conservative approach is recommended in asymptomatic patients diagnosed with DTF that can be followed through watchful waiting.