Staghorn sign: Extra-abdominal desmoid fibromatosis.

Extra-abdominal desmoid fibromatosis, also known as aggressive fibromatosis, is a slow growing benign tumour that arises from fascia or aponeuroses of muscles. The tumour characteristically grows along fascial planes and can infiltrate subcutaneous tissues and muscles. The pattern of subcutaneous spread seen on ultrasound has been described to resemble a branching staghorn. This represents the local invasion (from the deeper tumour) along fibrous septa into the subcutaneous fat. On CT the tumour is of soft tissue density, similar to muscle, with variable density. On MRI the tumour is again heterogeneous reflecting the mixture of collagen, spindle cells and extra-cellular matrix.

The purpose of this study is to clarify the relationship of the staining pattern of beta-catenin with the CTNNB1 mutation status and various clinical variables, and investigate the significance of immunohistochemical staining of beta-catenin in cases diagnosed with DF. Between 1997 and 2017, 104 cases diagnosed with DF from 6 institutions in Japan were enrolled in this study. For all cases, immunohistochemical staining of beta-catenin and gene mutation analysis of CTNNB1 were performed. Of 104 cases, 87 (84%) showed nuclear staining of beta-catenin, and 95 (91%) positive staining in cytoplasm. The proportion of cases showing strong nuclear staining of beta-catenin was significantly higher in the cases with S45F than in those with T41A or wild type (WT). The proportion of cases stained strongly in the cytoplasm rather than in the nucleus was significantly higher in the group of T41A than that of S45F or WT. Among 17 cases in which nuclear immunostaining were absent, CTNNB1 mutation was observed in 5 cases (29.4%). There were unignorable cases of DF with negative beta-catenin immunostaining despite a definitive clinical and pathological diagnosis of DF and/or positive CTNNB1 mutation.

We present the case of an 82-year-old male with constitutional syndrome. A computed tomography was performed, which identified a 69 x 52mm mass in the oesophago-gastric union. A computed tomography guided biopsy was performed and the histological analysis identified a fusocellular tumor compatible with desmoid fibromatosis. Treatment was started with indomethacin. However, a control computed tomography 3 months later showed that the mass had grown. Thus, indomethacin treatment was stopped and tamoxifen treatment was started. The patient has had an excellent performance status since symptom presentation. In conclusion, desmoid tumors are rare and most are sporadic. However, they may also be associated with familial adenomatous polyposis syndrome. It must be emphasized that our patient did not have any risk factors and the anatomical location in the oesophago-gastric union is not a common location. Desmoid fibromatosis supposes a clinical challenge for diagnosis and treatment and thus, management should be individualized.

The diagnosis of spindle cell lesions of the breast parenchyma is challenging. Some of these lesions share the expression of CD34, posing differential diagnostic problems, especially in core biopsies. Recently, antibodies against the STAT6 C-terminal, are being used in paraffin-embedded tissues as a surrogate for identifying the NAB2ÐSTA6 fusion gene which is considered a specific molecular marker for solitary fibrous tumor. Accordingly, we investigated the expression of STAT6 in a large series of uncommon spindle cell tumor-like and tumor lesions occurring primarily in the breast parenchyma. We collected 10 classic-type myofibroblastomas, 9 desmoid-type fibromatosis, 6 spindle cell metaplastic carcinoma, 5 benign fibroblastic spindle cell tumors, 3 solitary fibrous tumors, 7 pseudoangiomatous stromal hyperplasias, 2 reactive spindle cell nodules, 1 leiomyoma, 1 spindle cell lipoma, 1 case of inflammatory pseudotumor, 1 nodular fasciitis, 1 myxoma and 1 dermatofibrosarcoma protuberans. A diffuse and strong nuclear STAT6 expression was restricted only to solitary fibrous tumors, while the other lesions were negative or showed only weak cytoplasmic expression. The present study confirms that the demonstration of a diffuse and strong STAT6 nuclear staining is very helpful in distinguishing solitary fibrous tumor from other spindle cell mimics arising in the breast.

The aim of this retrospective cohort study was to review urological complication rates arising from familial adenomatous polyposis associated desmoid tumours and their management. Clinicians should actively survey the renal tract at regular intervals after a diagnosis of an intra-abdominal desmoid tumour as complications can arise insidiously, at any stage.

Familial adenomatous polyposis (FAP) is usually caused by germline mutations in the adenomatous polyposis coli (APC) gene. The classic form is characterized by hundreds to thousands of adenomas in the colorectum and early onset colorectal cancer (CRC) if left untreated. FAP is also associated with multiple extra-colonic manifestations such as gastroduodenal polyps, osteomas, epidermoid cysts, fibromas and desmoids. Most desmoid tumours in FAP patients occur intra-abdominally. Approximately 15-20% of the APC mutations are de novo mutations. Somatic mosaicism has been reported in some sporadic cases of polyposis but is probably an underestimated cause of the disease. This case report presents the detection of a mosaic APC mutation in a 26-year-old woman who as a child had been diagnosed with desmoid type fibromatosis. FAP was suggested when she presented with extensive extra abdominal fibromatosis. Our findings indicate that APC mutations may be suspected in patients presenting with a desmoid regardless of its location. If there is clinical evidence that the patient has FAP, adenomas and colonic mucosa in addition to leukocyte DNA should be included in the screening, preferably using methods that are more sensitive than Sanger sequencing.