Fibromatosis of the breast and mutations involving the APC/beta-catenin pathway

The conundrum of breast cancer mimics

The BIRADS lexicon ensures a standard reporting terminology in breast imaging and serves as a means of smooth communication between the radiologist and the referring physician. BIRADS assessment categories 4 and 5 warrant a biopsy to rule out underlying malignancy. However, a substantial number of cases in these categories sometimes turn out to be benign on biopsy. These benign mimics encompass inflammatory, sclerosing, neoplastic and a few other miscellaneous conditions. Awareness of these various mimics of breast cancer can equip the radiologist to handle these apparent cases of radiologic-pathological (rad-path) discordance better, guide overall patient management, avoiding inadvertent excisional biopsies and help alleviate patient anxiety and confusion.

Diagnosis and Management of Desmoid Fibromatosis of the Breast

Desmoid fibromatosis of the breast (also known as desmoid tumor of the breast) is a rare entity infrequently encountered by oncologists and surgeons caring for patients with breast disease. The current body of literature is highly reliant on case series and extrapolations from other sites of desmoid tumor-related disease. Much remains unclear regarding the pathological origins, natural history, and response to treatment of this condition. Traditional treatment strategies have centered on surgical resection, which may result in significantly disfiguring cosmetic and functional outcomes, frequent need for re-operation, and associated morbidity. There are limited data to support the superiority of upfront surgical resection when compared to medical therapy or watchful waiting strategies. Current treatment guidelines for desmoid tumors do not focus on the breast as a site of disease and are purposefully ambiguous due to the paucity of evidence available. We aim to review the literature concerning desmoid fibromatosis of the breast and propose an algorithm for current evidence-based management of this rare disease in the context of our experience with this pathology at a high-volume quaternary referral center.

Infantile Sinonasal Myxoma Is Clinically and Genetically Distinct From Other Myxomas of the Craniofacial Bones and From Desmoid Fibromatosis

Sinonasal myxomas are rare benign tumors of the maxillary bone and sinus. There is published evidence that sinonasal myxomas occurring in children up to 3 years of age ("infantile sinonasal myxomas") are clinically distinctive and harbor Wnt signaling pathway alterations. Here, we characterized 16 infantile sinonasal myxomas and compared them to 19 maxillary myxomas and 11 mandibular myxomas in older patients. Clinical follow-up was available for 21 patients (46%) overall (median: 2.6 y; range: 4 mo to 21 y), including 10 of 16 infantile sinonasal myxomas (62%). None of the 8 resected infantile sinonasal myxomas recurred, despite positive margins in 6 of them. One incompletely resected infantile sinonasal myxoma underwent partial regression without additional treatment. In contrast, 4 of the 11 other myxomas with follow-up recurred (36%), including one that recurred twice. Imaging studies demonstrated all infantile sinonasal myxomas to be expansile lesions arising from the anterior maxillary bone adjacent to the nasal aperture, with peripheral reactive bone formation. Histologically, infantile sinonasal myxomas showed short, intersecting fascicles of bland fibroblastic cells with prominent stromal vessels. Examples with collagenous stroma showed some morphologic overlap with desmoid fibromatosis, although none showed infiltrative growth into adjacent soft tissue. Immunohistochemistry demonstrated nuclear β-catenin expression in 14 of 15 infantile sinonasal myxomas (93%), in contrast to 4 of 26 other myxomas of craniofacial bones (15%). Smooth muscle actin was expressed in only 1 of 11 infantile sinonasal myxomas (9%). Next-generation sequencing was successfully performed on 10 infantile sinonasal myxomas and 7 other myxomas. Infantile sinonasal myxomas harbored CTNNB1 point mutations in 4 cases (D32Y, G34E, G34R, and I35S), and none harbored alterations to the phosphorylation sites T41 and S45 that are altered in 99% of CTNNB1 -mutant desmoid fibromatoses. Three tumors showed alterations consistent with biallelic APC inactivation. Three infantile sinonasal myxomas that showed strong nuclear β-catenin expression were negative for CTNNB1 and APC alterations. Sequencing was negative for CTNNB1 or APC alterations in all 7 myxomas of craniofacial bones in older patients. Four of these myxomas in older patients (57%) showed copy number alterations, and all lacked known driving alterations. These findings support the notion that infantile sinonasal myxomas are clinically and genetically distinctive, and we propose the use of the diagnostic term "infantile sinonasal myxoma" to distinguish this tumor type from other myxomas of the craniofacial bones. Infantile sinonasal myxoma should be distinguished from desmoid fibromatosis because of its unique clinical presentation, more indolent clinical behavior, different morphology, different immunohistochemical profile, and different genetics. Given its indolent behavior even when marginally excised, infantile sinonasal myxoma can be managed with conservative surgery.

Alginate-Chitosan Hydrogels Containing shRNA Plasmid for Inhibition of CTNNB1 Expression in Breast Cancer Cells

The hydrogels prepared with alginate and chitosan polymers were prepared to deliver the shRNA-encoding plasmid (pshRNA) to MDA-MB-231 cells for the inhibition of β-catenin (CTNNB1), which was reported to be overexpressed in breast cancer. Polyion complex hydrogels prepared using sodium alginate and chitosan were characterized by Fourier transform infrared spectrometry (FTIR) analysis, scanning electron microscope (SEM) analysis, swelling, and degradation properties. After the release properties and serum stability of pshRNA-loaded hydrogels were determined, their cytotoxicity, transfection efficacy, and effects on CTNNB1 expression were investigated in MDA-MB-231 cells. All hydrogels were shown to protect pshRNA from the enzymatic activity of serum and to deliver pshRNA to cells efficiently. As a result of transfection studies, pshRNA-loaded hydrogels reduced CTNNB1 expression by up to 30.25%. Cell viability also decreased by 38% in cells treated with 2.5% (w/v) alginate-chitosan hydrogel containing pshRNA targeting CTNNB1. Alginate-chitosan hydrogels were shown to be a suitable matrix system for local gene delivery.

Increased Expression of LEF1 and β-Catenin in Invasive Micropapillary Carcinoma of the Breast is Associated With Lymphovascular Invasion and Lymph Node Metastasis

Invasive micropapillary breast carcinoma (IMPC) is a rare breast cancer subtype characterized by small tumor cell clusters with loss of stromal attachment, an inside-out growth appearance, and lymphotropism. IMPC is associated with high incidence of lymphovascular invasion (LVI) and lymph node metastasis. Activated Wnt signaling has been implicated in the metastasis of other aggressive breast tumors, including triple-negative and basal-like carcinomas. In this study, we tested whether activated Wnt signaling could be detected in IMPC. Upon ligand binding, the central mediator of the Wnt pathway, β-catenin, accumulates in the cytosol and translocates to the nucleus where it forms a complex with lymphoid enhancer-binding factor 1 (LEF1) to regulate transcription. We performed immunostaining for β-catenin and LEF1 on a well-annotated cohort of 40 breast tumors and nodal metastases displaying micropapillary histopathology. Strong nuclear accumulation of β-catenin was not observed, however a dim cytosolic and/or nuclear accumulation of β-catenin was sometimes seen in IMPC and this expression pattern was significantly associated with nodal metastasis. β-catenin expression correlated with the upregulation of LEF1 in IMPC. LEF1 expression was detected in 26 of 40 (65%) cases and was specifically enriched at the invasive front of the tumor and in tumor clusters undergoing LVI. Detection of LEF1 expression in the primary tumor was associated with an increased rate of LVI, lymph node metastasis, and disease relapse. LEF1 and β-catenin expression levels were significantly higher in metastases compared with primary tumors. In summary, this study demonstrates an association between the upregulation of β-catenin/LEF1 and the metastasis of IMPC.

Low to Intermediate (Borderline) Grade Breast Spindle Cell Lesions on Needle Biopsy: Diagnostic Approach and Clinical Management

Spindle cell proliferations of the breast are a heterogeneous group of lesions ranging from benign or reactive lesions to aggressive malignant neoplasms. Diagnosis on core biopsy can be particularly challenging as lesions displaying different lineages associated with variable outcomes share overlapping morphologies (scar vs. fibromatosis-like metaplastic carcinoma) whereas individual entities can exhibit a large variety of appearances (myofibroblastoma). In this review, lesions are grouped into lineage, when possible, including those showing fibroblastic/myofibroblastic differentiation, ranging from entities that require no additional management, such as scar and nodular fasciitis, to those with unpredictable clinical outcomes such as fibromatosis and solitary fibrous tumor or locally aggressive behavior such as dermatofibrosarcoma protuberans. The review of low-grade vascular lesions includes atypical vascular lesion and low-grade angiosarcoma. Also discussed are various adipocytic lesions ranging from lipoma to liposarcoma, and rare smooth muscle and neural entities more commonly encountered in locations outside the breast, such as leiomyoma, neurofibroma, schwannoma, or granular cell tumor. Optimal histological evaluation of these entities merges clinical and radiologic data with morphology and ancillary testing. We present our approach to immunohistochemical and other ancillary testing and highlight issues in pathology correlation with imaging. Recent updates in the management of breast spindle cell lesions are addressed. In a well-sampled lesion with radiographic concordance, the core biopsy diagnosis reliably guides management and we advocate the inclusion of management recommendations in the pathology report. Precise characterization using up to date guidelines is important to identify a subset of patients who may safely avoid unnecessary surgical procedures. A multidisciplinary approach with close collaboration with our clinical colleagues is emphasized.

Desmoid fibromatosis of the breast occurring after breast reduction surgery mimicking a carcinoma: A rare case report

Introduction

Desmoid tumors are benign mesenchymal tumors developed at the expense of muscular fasciae and aponeuroses. The mammary localization is a rare entity, representing less than 0.2% of all breast tumors. It is characterized by a strictly local evolution and its tendency to recur without giving metastases. Its clinical and radiological presentation is similar to a breast carcinoma which is the main differential diagnosis.

Case presentation

Patient aged 51 years, primigravida primiparous, followed for right breast cancer diagnosed at the age of 49 years for which she received a right mastectomy and axillary lymphnode dissection and contralateral breast reduction. It was a 4 cm infiltrating ductal carcinoma, SBR III Luminal B, 0 N+/20 N with presence of fibrous mastopathy without sign of malignancy at the left breast reduction specimen.The patient received adjuvant chemotherapy, external radiotherapy and hormone therapy.One year after surgery, the patient returned for a four x 2 cm left breast nodule in the upper medial quadrant. The biopsy confirmed the diagnosis of fibromatosis of the breast. A wide local excision was performed.

Discussion

The etiology of this tumor is unknown, however, physical, hormonal and genetic factors play an important role in the development of desmoid tumor.The clinical presentation is similar to breast carcinoma, making it difficult to differentiate this tumor from breast carcinoma. Breast imaging techniques are not specific for desmoid fibromatosis. Treatment is based primarily on complete surgical excision.

Conclusion

Breast fibromatosis is a rare entity, clinically and radiologically mimicking breast cancer. Only histology will provide the diagnosis. The treatment of choice is based on complete surgical excision with healthy safety margins.

•

Breast fibromatosis is an uncommon tumor with an uncertain etiology.

•

A breast carcinoma is the main differential diagnosis.

•

The current report discusses a case of desmoid type fibromatosis of the breast occurring after breast reduction surgery.

Breast Fibromatosis: Radiologic-Pathologic Correlation

Fibromatosis of the breast is a rare, benign locally infiltrative tumor without metastatic potential. Patients typically present with a painless, palpable, firm breast mass, which may be mobile or fixed to the pectoralis muscle. While some cases are related to familial mutations in the adenomatous polyposis coli (APC) gene, the majority are sporadic due to somatic mutations or prior injury to the breast tissue. On mammography, fibromatosis is typically seen as an irregular, dense, spiculated mass. US demonstrates a hypoechoic, irregular mass with indistinct margins. Fibromatosis is indistinguishable from breast cancer on imaging, and core biopsy is required for definitive diagnosis. Wide local excision is the historical standard for treatment; however, recurrence rates are high, and other emerging therapies are being explored. This article reviews the clinical features, imaging and histopathologic findings, along with brief overview of management.

A nonrandom association of breast implants and the formation of desmoid tumors

BACKGROUND

Studies suggest that surgical breast augmentation with implants is a risk factor for breast desmoid tumors. The statistical strength of this correlation is unknown, as evidence is limited to anecdotal reports.

METHODS

Patients with breast desmoid tumors and a history of breast implants seen at a single center between 2000 and 2021 were identified via radiology, breast, and sarcoma databases. The standardized incidence ratio (SIR) was calculated to assess the correlation between breast desmoid tumors and breast implants. The cases were pooled with published cases for analyses. Progression-free survival curves and hazard ratios were estimated using the Kaplan-Meier method and Cox proportional-hazards modeling.

RESULTS

Fourteen patients from one institution and 66 cases in the literature were identified. All patients were female, and the mean age was 38 years old (range 20-66). 63 patients (82%) underwent resection, 9 (12%) received chemotherapy, 3 (4%) received sorafenib, 11 (14%) received hormonal therapy, and 3 (4%) underwent active surveillance. After resection, the 2-year recurrence-free survival rate was 77% (95% CI 65%-89%). The recurrence risk was lower for resection with no residual tumor (R0) compared to microscopic (R1) or macroscopic (R2) residual tumor (HR: 0.15; 95% CI 0.02-0.8; p < 0.05). The SIR was 482 (95% CI 259-775) to 823 (95% CI 442-1322), suggesting a 482-823 times higher risk of developing a breast desmoid tumor after breast augmentation than the general population.

CONCLUSION

We present a nonrandom association between breast implants and desmoid tumors. Whether the tumors arise from the surgical trauma or the implant's biomaterial is unknown. When surgery is indicated, negative margins reduce the risk of recurrence.

Spindle cell lesions of the breast: a diagnostic approach

Spindle cell lesions of the breast comprise a heterogeneous group of lesions, ranging from reactive and benign processes to aggressive malignant tumours. Despite their rarity, they attract the attention of breast pathologists due to their overlapping morphological features and diagnostic challenges, particularly on core needle biopsy (CNB) specimens. Pathologists should recognise the wide range of differential diagnoses and be familiar with the diverse morphological appearances of these lesions to make an accurate diagnosis and to suggest proper management of the patients. Clinical history, immunohistochemistry, and molecular assays are helpful in making a correct diagnosis in morphologically challenging cases. In this review, we present our approach for the diagnosis of breast spindle cell lesions, highlighting the main features of each entity and the potential pitfalls, particularly on CNB. Breast spindle cell lesions are generally classified into two main categories: bland-appearing and malignant-appearing lesions. Each category includes a distinct list of differential diagnoses and a panel of immunohistochemical markers. In bland-appearing lesions, it is important to distinguish fibromatosis-like spindle cell metaplastic breast carcinoma from other benign entities and to distinguish fibromatosis from scar tissue. The malignant-appearing category includes spindle cell metaplastic carcinoma, stroma rich malignant phyllodes tumour, other primary and metastatic malignant spindle cell tumours of the breast, including angiosarcoma and melanoma, and benign mimics such as florid granulation tissue and nodular fasciitis.

Lobular Breast Cancer: Histomorphology and Different Concepts of a Special Spectrum of Tumors

Simple Summary

Invasive lobular breast cancer (ILC) is a special type of breast cancer (BC) that was first described in 1941. The diagnosis of ILC is made by microscopy of tumor specimens, which reveals a distinct morphology. This review recapitulates the developments in the microscopic assessment of ILC from 1941 until today. We discuss different concepts of ILC, provide an overview on ILC variants, and highlight advances which have contributed to a better understanding of ILC as a special histologic spectrum of tumors.

Abstract

Invasive lobular breast cancer (ILC) is the most common special histological type of breast cancer (BC). This review recapitulates developments in the histomorphologic assessment of ILC from its beginnings with the seminal work of Foote and Stewart, which was published in 1941, until today. We discuss different concepts of ILC and their implications. These concepts include (i) BC arising from mammary lobules, (ii) BC growing in dissociated cells and single files, and (iii) BC defined as a morpho-molecular spectrum of tumors with distinct histological and molecular characteristics related to impaired cell adhesion. This review also provides a comprehensive overview of ILC variants, their histomorphology, and differential diagnosis. Furthermore, this review highlights recent advances which have contributed to a better understanding of the histomorphology of ILC, such as the role of the basal lamina component laminin, the molecular specificities of triple-negative ILC, and E-cadherin to P-cadherin expression switching as the molecular determinant of tubular elements in CDH1-deficient ILC. Last but not least, we provide a detailed account of the tumor microenvironment in ILC, including tumor infiltrating lymphocyte (TIL) levels, which are comparatively low in ILC compared to other BCs, but correlate with clinical outcome. The distinct histomorphology of ILC clearly reflects a special tumor biology. In the clinic, special treatment strategies have been established for triple-negative, HER2-positive, and ER-positive BC. Treatment specialization for patients diagnosed with ILC is just in its beginnings. Accordingly, ILC deserves greater attention as a special tumor entity in BC diagnostics, patient care, and cancer research.

Targeting Wnt Signaling in Endometrial Cancer

Simple Summary

Wnt has diverse regulatory roles at multiple cellular levels and numerous targeting points, and aberrant Wnt signaling has crucial roles in carcinogenesis, metastasis, cancer recurrence, and chemotherapy resistance; based on these facts, Wnt represents an appealing therapeutic target for cancer treatment. Although preclinical data supports a role for the Wnt signaling pathway in uterine carcinogenesis, this area remains understudied. In this review, we identify the functions of several oncogenes of the Wnt/β-catenin signaling pathway in tumorigenesis and address the translation approach with potent Wnt inhibitors that have already been established or are being investigated to target key components of the pathway. Further research is likely to expand the potential for both biomarker and cancer drug development. There is a scarcity of treatment choices for advanced and recurrent endometrial cancer; investigating the sophisticated connections of Wnt signaling networks in endometrial cancer could address the unmet need for new therapeutic targets.

Abstract

This review presents new findings on Wnt signaling in endometrial carcinoma and implications for possible future treatments. The Wnt proteins are essential mediators in cell signaling during vertebrate embryo development. Recent biochemical and genetic studies have provided significant insight into Wnt signaling, in particular in cell cycle regulation, inflammation, and cancer. The role of Wnt signaling is well established in gastrointestinal and breast cancers, but its function in gynecologic cancers, especially in endometrial cancers, has not been well elucidated. Development of a subset of endometrial carcinomas has been attributed to activation of the APC/β-catenin signaling pathway (due to β-catenin mutations) and downregulation of Wnt antagonists by epigenetic silencing. The Wnt pathway also appears to be linked to estrogen and progesterone, and new findings implicate it in mTOR and Hedgehog signaling. Therapeutic interference of Wnt signaling remains a significant challenge. Herein, we discuss the Wnt-activating mechanisms in endometrial cancer and review the current advances and challenges in drug discovery.

Clinicopathological features of 70 desmoid-type fibromatoses confirmed by β-catenin immunohistochemical staining and CTNNB1 mutation analysis

Desmoid-type fibromatosis (DF) is a locally aggressive neoplasm characterized by mutations in the CTNNB1 gene, which encodes the β-catenin protein. We reviewed 85 cases of DF and performed Sanger sequencing for detecting mutations in CTNNB1 and immunostaining for detecting β-catenin localization. We included 70 DF samples, of which 56 cases demonstrated nuclear β-catenin localization and 43 cases harboured CTNNB1 mutations. CTNNB1-mutant DF samples consistently displayed nuclear β-catenin expression and were derived from larger-sized tumours compared to samples with wild-type CTNNB1. When we further classified DF cases into 2 subgroups based on the type of specimen, excised specimens with nuclear β-catenin expression frequently displayed CTNNB1 mutation and no statistical correlation between nuclear β-catenin expression and CTNNB1 mutation was observed in biopsies. When we classified CTNNB1 mutation cases into 2 subgroups (DF with T41A or T41I, and DF with S45F or S45P), T41A or T41I mutations were observed more frequently in males than in females. Additionally, DF tumours harbouring S45F or S45P mutations were located more frequently in the abdominal wall than tumours with T41A or T41I mutations. In conclusion, CTNNB1 mutation correlates with nuclear β-catenin expression in larger or excised DF tumours, and DF harbouring CTNNB1 mutations manifest variable clinical presentations.

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/β-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.

Clinicopathological and radiological characterization of myofibroblastoma of breast: A single institutional case review

Myofibroblastoma is a rare type of benign myofibroblastic neoplasm in the breast. It is clinically presented as a well-circumscribed mass, usually small in size (usually less than 4.0 cm), and can mostly be cured by local excision. Rare cases of giant myofibroblastoma greater than 10 cm have been reported, but also follow a benign clinical course. Histologically, breast myofibroblastoma is featured by bland fascicles of spindle cells intermixed with thick hyalinized collagen bundles. Mast cells are frequently found within the stroma. However, a wide spectrum of morphological variants can occur in myofibroblatoma, making its diagnosis challenging sometimes. Differential diagnosis of myofibroblastoma with other spindle cell lesions in the breast, either benign or malignant, is also important in practice. In this study, we collected 15 cases of breast myofibroblastoma diagnosed in our institution during a 20 year period. The sizes of these cases range from 0.4 cm to 35.2 cm (mean is 3.7 cm). To our knowledge, the case of giant breast myofibroblastoma we presented here is the largest one reported to date. The histological examination of the cases show great morphological variations. Besides the classical type, features of cellular, collagenized, palisading, epithelioid, myxoid, myoid, solitary fibrous tumor-like are also identified in the case series. Immunohistochemical staining patterns as well as clinical features of the cases are also summarized and compared. All cases in this study show no recurrence on follow-up. In addition, cases that are important differential diagnosis for breast myofibroblastoma are also studied. Their key histological characteristics are compared with myofibroblastoma, and their immunohistochemical and molecular features are discussed.

Fibromatosis of the breast: a 10-year multi-institutional experience and review of the literature

BACKGROUND

Breast fibromatosis is a rare clinical entity, but poses significant diagnostic and therapeutic challenges. In light of recent changes in management practices, the aim was to review our institutional experience of breast fibromatosis and provide a review of current available literature on such management.

METHODS

A search of pathological databases within two tertiary institutions for all patients diagnosed with fibromatosis of the breast over a 10-year period (2007-2016) was performed. Clinicopathological characteristics and modes of treatment were recorded for each patient. Concurrently a comprehensive literature search was performed and studies relating to breast fibromatosis and its management were identified and reviewed.

RESULTS

Sixteen patients were identified. Median age at diagnosis was 42 (range 21-70) and all patients were diagnosed with core biopsy. The most useful imaging modality in diagnosis was ultrasonography and magnetic resonance imaging. 13/16 were treated surgically whilst 3/16 were treated using a watch-and-wait approach. 6/13 (46%) required re-excision of margins and 2/13 (15%) had recurrence after surgery. On review of the literature, there is no dedicated guideline in place for the management of breast fibromatosis. Currently a 'watch and wait' approach is favoured over surgical intervention due to high levels of recurrence and associated surgical morbidity. All cases should be discussed at a sarcoma multidisciplinary team meeting and tyrosine kinase inhibitors should be considered in advanced cases.

CONCLUSIONS

Breast fibromatosis is rare but affects young patients. Active surveillance is now favoured over surgical resection due to high recurrence rates and extensive morbidity. Dedicated guidelines are required to ensure best outcomes.

Cellular Spindled Histiocytic Pseudotumor: A Benign Mimic of Spindle Cell Neoplasia of the Breast

CONTEXT.—

Cellular spindled histiocytic pseudotumor (CSHPT) is an exuberant, dense histiocytic proliferation seen in the setting of mammary fat necrosis. CSHPT has a broad histologic differential diagnosis, including benign, malignant, and inflammatory etiologies.

OBJECTIVES.—

To highlight the most important histologic and immunohistochemical findings of CSHPT and provide comparisons to entities within the broad differential diagnosis.

DATA SOURCES.—

Recently published literature regarding CSHPT and other diagnostic considerations.

CONCLUSIONS.—

CSHPT is a benign histiocytic proliferation with a broad differential diagnosis, for which comprehensive ancillary studies may be required to exclude malignant and infectious entities.

Aberrant WNT/CTNNB1 Signaling as a Therapeutic Target in Human Breast Cancer: Weighing the Evidence

WNT signaling is crucial for tissue morphogenesis during development in all multicellular animals. After birth, WNT/CTNNB1 responsive stem cells are responsible for tissue homeostasis in various organs and hyperactive WNT/CTNNB1 signaling is observed in many different human cancers. The first link between WNT signaling and breast cancer was established almost 40 years ago, when Wnt1 was identified as a proto-oncogene capable of driving mammary tumor formation in mice. Since that discovery, there has been a dedicated search for aberrant WNT signaling in human breast cancer. However, much debate and controversy persist regarding the importance of WNT signaling for the initiation, progression or maintenance of different breast cancer subtypes. As the first drugs designed to block functional WNT signaling have entered clinical trials, many questions about the role of aberrant WNT signaling in human breast cancer remain. Here, we discuss three major research gaps in this area. First, we still lack a basic understanding of the function of WNT signaling in normal human breast development and physiology. Second, the overall extent and precise effect of (epi)genetic changes affecting the WNT pathway in different breast cancer subtypes are still unknown. Which underlying molecular and cell biological mechanisms are disrupted as a result also awaits further scrutiny. Third, we survey the current status of targeted therapeutics that are aimed at interfering with the WNT pathway in breast cancer patients and highlight the importance and complexity of selecting the subset of patients that may benefit from treatment.

Breast fibromatosis: Making the case for primary vs secondary subtypes

Fibromatosis of the breast is a rare condition that can be locally aggressive. The mainstay of treatment remains wide local excision, with varied adjuvant therapy as needed. The authors describe their experience in the treatment of a series of patients and propose the classification of primary and secondary breast fibromatosis. A single-institution retrospective analysis of patients treated for breast fibromatosis from 2003 to 2017 was completed. Demographic data, pertinent past medical history, and treatment modalities were reviewed. Primary breast fibromatosis was defined as arising in the absence of previous surgery or radiation therapy to the ipsilateral breast. Secondary breast fibromatosis was defined as arising in the setting of previous surgery or radiation therapy to the ipsilateral breast. A total of 16 patients were included with the median age 40 (28-64) years. The average size of the lesion was 6.37 cm (range of 1.5-15 cm). Mean follow-up time was 65 months. Surgical excision was completed in 14 patients, with two recurrences. There were no recurrences in patients with surgical margins >1 cm. Two patients were treated nonsurgically. There were seven patients with primary fibromatosis of the breast and nine patients with secondary fibromatosis of the breast. Fibromatosis of the breast is difficult to diagnose prior to surgical excision. We advocate for the multi-disciplinary treatment of this disease process with an aggressive surgical approach to achieve margins >1 cm.

Gap Junctions and Wnt Signaling in the Mammary Gland: a Cross-Talk?

Connexins (Cxs), the building blocks of gap junctions (GJs), exhibit spatiotemporal patterns of expression and regulate the development and differentiation of the mammary gland, acting via channel-dependent and channel-independent mechanisms. Impaired Cx expression and localization are reported in breast cancer, suggesting a tumor suppressive role for Cxs. The signaling events that mediate the role of GJs in the development and tumorigenesis of the mammary gland remain poorly identified. The Wnt pathways, encompassing the canonical or the Wnt/β-catenin pathway and the noncanonical β-catenin-independent pathway, also play important roles in those processes. Indeed, aberrant Wnt signaling is associated with breast cancer. Despite the coincident roles of Cxs and Wnt pathways, the cross-talk in the breast tissue is poorly defined, although this is reported in a number of other tissues. Our previous studies revealed a channel-independent role for Cx43 in inducing differentiation or suppressing tumorigenesis of mammary epithelial cells by acting as a negative regulator of the Wnt/β-catenin pathway. Here, we provide a brief overview of mammary gland development, with emphasis on the role of Cxs in development and tumorigenesis of this tissue. We also discuss the role of Wnt signaling in similar contexts, and review the literature illustrating interplay between Cxs and Wnt pathways.

Is immunohistochemical staining for β-catenin the definitive pathological diagnostic tool for desmoid-type fibromatosis? A multi-institutional study

Immunohistochemical staining with anti-β-catenin antibody has been applied as a diagnostic tool for desmoid-type fibromatoses (DFs). In recent years, specific gene mutation (CTNNB1) analysis has also been reported to be useful for diagnosis of DF; however, the association between CTNNB1 mutation status and immunohistochemical staining pattern of β-catenin is rarely reported. The purposes of this study are to clarify the relationship of the staining pattern of β-catenin with the CTNNB1 mutation status and various clinical variables, and to investigate the significance of immunohistochemical staining of β-catenin in cases diagnosed as DF. Between 1997 and 2017, 104 cases diagnosed as DF from 6 institutions in Japan were enrolled in this study: Nagoya University, National Cancer Center Hospital, Niigata University, Okayama University, Kyushu University, and Cancer Institute Hospital. For all cases, immunohistochemical staining of β-catenin and gene mutation analysis of CTNNB1 were performed. Of 104 cases, 87 (84%) showed nuclear staining of β-catenin, and 95 (91%) showed positive staining in the cytoplasm. The proportion of cases showing strong nuclear staining of β-catenin was significantly higher in the cases with S45F than in those with T41A or wild type. 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 wild type. Among 17 cases in which nuclear immunostaining was absent, CTNNB1 mutation was observed in 5 cases (29.4%). There were unignorable cases of DF with negative β-catenin immunostaining despite a definitive clinical and pathological diagnosis of DF and/or positive CTNNB1 mutation.

Bilateral breast fibromatosis after silicone prosthetics in a patient with classic familial adenomatous polyposis: A case report

Breast fibromatosis is a benign fibroblastic proliferation accounting for less than 0.2% of breast tumors. It presents sporadically or as a manifestation of familial adenomatous polyposis (FAP). Fibromatosis in FAP may develop in patients with adenomatous polyposis coli (APC) gene mutations at any location through the gene. Notably, there is an increased risk if mutation is downstream codon 1400. The present case report described a 33-year-old woman with recurrent bilateral breast fibromatosis after breast implants in a context of classic FAP. APC mutation (codon-935) was detected at the age of 16. In the same year, a thyroidectomy for a cribriform-morular papillary thyroid carcinoma (pT1) was performed. Seven years later, a prophylactic total colectomy with >100 adenomas without invasive carcinoma was performed and the patient was kept under surveillance. At the age of 30 years old, she underwent breast silicone implantation for cosmetic reasons. One year later, bilateral breast tumors were diagnosed in core biopsy as fibromatosis (nuclear β-catenin+, estrogen receptors-). After no success with medical treatment with tamoxifen, bilateral mastectomy was performed. The patient relapsed one year later and a fibromatosis lesion in the right thoracic wall was excised again. The patient demonstrated no signs of relapse 24 months after the surgery. This rare case illustrates that the increased risk of developing fibromatosis in patients with FAP, even in the classic form, should be considered before deciding to place breast implants.

Aggressive breast fibromatosis following augmentation mastoplasty: a series of case reports

Aggressive fibromatosis comprises connective tissue tumours that represent 0.03% of all bodily neoplasms, occurring more often in the abdominal wall, mesentery, and extremities; its location in the breast constitutes a very infrequent type of lesion. Its pathogenesis is diverse and its relationship with augmentation mastoplasty is still unclear. Four cases of aggressive breast fibromatosis following augmentation mastoplasty are reported in this article.

Proof of concept: prognostic value of the plasmatic concentration of circulating cell free DNA in desmoid tumors using ddPCR

Since desmoid tumors (DT) exhibit an unpredictable clinical course, with stabilization and/or spontaneous regression, an initial "wait-and-see" policy is the new standard of care-thus, the actual challenge is to identify early factors of progression. We present a method of detection of CTNNB1 mutations using a targeted digital droplet PCR (ddPCR) on cell-free DNA (cfDNA) extracted from blood samples of 31 DT patients. Furthermore, we analyzed the correlation between DT evolution and plasmatic concentration of total and mutated cfDNA at the time of diagnosis. Circulating copies of CTNNB1 mutants (ctDNA) were detected in the plasma of 6 patients (33%) but their concentration was not correlated with evolution of the tumor. Concentration of total cfDNA was higher in the plasma of patients with progressive desmoids (p = 0,0009). Using a threshold <900 copies/mL of plasma to detect indolent desmoid and a threshold >1375, it was possible to predict desmoid evolution for 65% of patients by measuring the quantity of circulating DNA in their plasma as early as the time of diagnosis. Albeit showing that the detection of CTNNB1 mutants is possible in the plasma of patients harboring a desmoid tumor, the results of this preliminary study raise the hypothesis that most of the circulating DNA detected in their plasma is derived from non-neoplastic cells, most likely normal neighboring tissues being actively invaded. Our results open the perspective of using cfDNA as a biomarker to predict prognosis at the time of diagnosis and assess tumor dynamics to optimize the treatment strategy.

Desmoid Tumor and Silicone Breast Implant Surgery: Is There Really a Connection? A Literature Review

BACKGROUND

Desmoid tumors are borderline tumors of the connective tissue, arising in the musculo-aponeurotic stromal elements. A desmoid tumor (DT) has an infiltrative and locally aggressive growth pattern and usually does not metastasize; however, it has a high recurrence and complication rate. DT located in the breast (BDT) represents a rare extra-abdominal form. Recently, the presence of breast silicone implants was suggested by several researchers as a risk factor for developing BDT.

OBJECTIVES

The goal of this review is to investigate the possible correlation between BDT and breast implant surgery.

METHODS

We conducted a literature review of BDT-reported cases, associated with breast implant surgery.

RESULTS

The search revealed 36 cases of BDT associated with silicone breast implants.

CONCLUSIONS

Based on the reviewed data, the incidence of BDT following breast implant surgery is lower than BDT in the general population. At the moment, a possible association between breast implants and the development of breast desmoid tumors cannot be unequivocally confirmed. A world registry with accurate documentation of each case of BDT associated with breast implant surgery should be performed for future investigation.

LEVEL OF EVIDENCE II

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Fibromatosis, a benign breast disease mimicking carcinoma. A case report

Introduction

Fibromatosis is an uncommon breast lesion that can mimic breast carcinoma in its clinical presentation.

Case summary

We present a clinical case in which a diagnosis and treatment dilemma existed, in terms of ultrasound findings that were not clear and suspicious, as well as results of Fine needle aspiration cytology. Our findings are compared with previous published cases. Also, literature review regarding fibromatosis presentation and diagnosis has been discussed, as well as treatment options.

Conclusion

Management of breast fibromatosis remains controversial because of the low incidence and further efforts needed to establish evidence-based treatment guidelines.

Radiologic images of an aggressive implant-associated fibromatosis of the breast and chest wall: case report and review of the literature

Fibromatosis of the breast is a rare benign disease compromising <0.2% of all primary breast tumors. Although the chest wall is a common location, occurrences of implant-associated fibromatosis of the breast are extremely rare; only 33 cases have been reported. We present a case of a 42-year-old female who underwent breast augmentation with silicone breast implants, and 2 years later developed an aggressive implant-associated fibromatosis of the breast and chest wall. On imaging studies, the tumor mimicked breast carcinoma, and despite chemotherapy, the fibromatosis rapidly enlarged and was locally invasive requiring wide surgical excision. Unlike previously reported imaging findings, magnetic resonance imaging revealed an oval circumscribed mass with fringe-like internal architecture. We provide a review of the literature and discuss the imaging features of implant-associated fibromatosis of the breast.

Myofibroblastic, fibroblastic and myoid lesions of the breast

Myofibroblastic, fibroblastic and/or myoid lesions are rare in the breast but comprise the majority of mammary mesenchymal spindle cell lesions. Whereas most have similar features to their counterparts at extramammary sites, pseudoangiomatous stromal hyperplasia is considered a breast-specific myofibroblastic proliferation on the same spectrum as myofibroblastoma. Other lesions with myofibroblastic/fibroblastic differentiation include fibromatosis and nodular fasciitis, as well as more aggressive tumors such as the rarely reported myofibrosarcoma, inflammatory myofibroblastic tumor and fibrosarcoma. Lesions with myoid differentiation include benign leiomyoma, myoid hamartoma and leiomyomatous myofibroblastoma, but primary leiomyosarcoma and rhabdomyosarcoma may also rarely arise in the breast. Furthermore, fibroepithelial lesions and metaplastic carcinomas can demonstrate myoid metaplasia. Diagnosis can be challenging, particularly on core biopsy, but benign lesions with or without recurrence potential must be distinguished from more aggressive tumors, especially metaplastic carcinoma and phyllodes tumors. This article will review lesions with myofibroblastic, fibroblastic and myoid differentiation in the breast, with special emphasis on differential diagnosis.

Medical treatment of mammary desmoid-type fibromatosis: which benefit?

Background

Breast fibromatosis is a rare disease characterized by monoclonal fibroblast proliferation. It has no ability to metastasize but has a high local recurrence rate and often infiltrates surrounding tissues. Surgical treatment is the reference, but recently, new targeted therapies have emerged. We report an original case of a patient with breast fibromatosis who received exclusive medical treatment. Our aim was to analyze these treatments based on the clinical and radiological outcome, iatrogenic effects, and pharmacological action.

Case presentation

We report the case of a 19-year-old woman who developed a desmoid-type fibromatosis of the lower inner quadrant of the right breast, measuring 50 × 25 mm (i.e., a volume of 27.4 cm³). Initial surgery was not possible because of potential esthetic and functional prejudice. Thus, she had an exclusive medical treatment including several lines: NSAIDs with tamoxifen and triptorelin, followed by sorafenib, then interferon α2b, and finally sunitinib. With tyrosine-kinase inhibitors (TKIs) (sunitinib), a significant partial response was observed (57% reduction of the maximal tumoral volume). For each treatment, we provided the clinical and radiological outcome in association with known pharmacological action.

Conclusions

TKI had been an interesting alternative option to initial surgery, providing at least a partial response and potentially allowing less mutilating surgery. However, no pharmacological mechanism can unequivocally explain TKI efficacy. In general, breast fibromatosis should be treated along with oncologist and interventional radiologists in a trans-disciplinary modality, thus offering an adapted treatment for this particular desmoid-type fibromatosis localization.

An approach to the diagnosis of spindle cell lesions of the breast

Although most breast spindle cell lesions (BSCLs) are rare, they constitute a wide spectrum of diseases, ranging from reactive processes to aggressive malignant tumours. Despite their varied histogenesis and behaviour, some lesions show an overlap of morphological features, making accurate diagnosis a challenging task, particularly in needle core biopsies. Clinical history and immunohistochemistry can help in making a correct diagnosis in morphologically challenging cases. To make an accurate diagnosis, it is important to maintain a wide differential diagnosis and be familiar with the diverse morphological appearances of these different entities. BSCLs can generally be classified into bland-looking and malignant-looking categories. In the former, the commonest diagnosis is scarring. However, it is important to distinguish low-grade spindle cell metaplastic breast carcinoma from other benign entities, as the management is clearly different. In the malignant category, it is important to differentiate metaplastic carcinoma from other malignant primary and metastatic malignant spindle cell tumours of the breast, such as malignant phyllodes tumour, angiosarcoma, and melanoma. This review focuses on the classification and histological and molecular diagnosis of various BSCLs, with an emphasis on the diagnostic approach, including in core biopsies.

Mammary Development and Breast Cancer: A Wnt Perspective

The Wnt pathway has emerged as a key signaling cascade participating in mammary organogenesis and breast oncogenesis. In this review, we will summarize the current knowledge of how the pathway regulates stem cells and normal development of the mammary gland, and discuss how its various components contribute to breast carcinoma pathology.

Mesenchymal tumors and tumor-like lesions of the breast: a contemporary approach review

The classification of the breast tumors has been revised and recently published in 2012 in the WHO blue book. Contrary to the epithelial tumors in the breast, mesenchymal tumors are rare and the classification for benign and malignant tumors is based on the same criteria in both categories, since no other specific diagnostic criteria, which would have an impact on prognosis, exist to date. The present review deals with minor changes mirroring the recent developments in the benign mesenchymal tumors (new additions are nodular fasciitis and atypical vascular lesions, while the haemangiopericytoma is removed) focusing especially on criteria to diagnose sarcomas, which represent a wide spectrum including very difficult lesions. The majority of sarcomas of the breast arise as a component of a malignant phyllodes tumor, while the pure forms are very rare. When a pure primary sarcoma of the breast is diagnosed, pathologists are encouraged to categorize the lesion according to the type of differentiation and to provide to the clinicians all the important prognostic parameters for the best treatment choice.

Wip1 phosphatase in breast cancer

Understanding the factors contributing to tumor initiation, progression and evolution is of paramount significance. Among them, wild-type p53-induced phosphatase 1 (Wip1) is emerging as an important oncogene by virtue of its negative control on several key tumor suppressor pathways. Originally discovered as a p53-regulated gene, Wip1 has been subsequently found amplified and more recently mutated in a significant fraction of human cancers including breast tumors. Recent development in the field further uncovered the utility of anti-Wip1-directed therapies in delaying tumor onset or in reducing the tumor burden. Furthermore, Wip1 could be an important factor that contributes to tumor heterogeneity, suggesting that its inhibition may decrease the rate of cancer evolution. These effects depend on several signaling pathways modulated by Wip1 phosphatase in a spatial and temporal manner. In this review we discuss the recent development in understanding how Wip1 contributes to tumorigenesis with its relevance to breast cancer.

Expression and significance of Wnt signaling components and their target genes in breast carcinoma

The aim of this study was to investigate the expression of β-catenin, axin, cyclin D1 and c-myc, and their correlation with various clinicopathological factors of breast carcinoma. Using immunohistochemistry, the expression of axin, β-catenin, cyclin D1 and c-myc proteins was detected in 168 breast carcinomas and 40 normal breast tissue samples, as well as in 72 breast intraductal proliferative lesions. Correlations among the expression of these proteins with the clinicopathological factors of breast carcinomas were subsequently analyzed. Gene mutations of β-catenin (exon 3) in 44 cases of breast carcinoma were analyzed using polymerase chain reaction (PCR) followed by direct sequencing. In normal tissue, the epithelial cells demonstrated a marked membranous expression of β-catenin protein at cell-cell boundaries and positive axin expression; cyclin D1 and c-myc expression, however, were negative. The abnormal rate of β-catenin expression and the overexpression of cyclin D1 and c-myc were higher in breast carcinomas compared with breast cystic hyperplasia tissues. Positive axin expression levels were lower in breast carcinomas compared with breast intraductal proliferative lesions and normal breast tissues. Axin expression correlated inversely with tumor size, histological grade, clinical tumor, node, metastasis (TNM) stage and lymph node metastasis. The abnormal expression of β-catenin and the overexpression of cyclin D1 were correlated, and the overexpression of c-myc was correlated with tumor size, histological grade, clinical TNM stage and lymph node metastasis. The abnormal expression of β-catenin was correlated with the overexpression of cyclin D1, but not with the overexpression of c-myc. Lower levels of axin expression were correlated with higher levels of nuclear β-catenin expression. Mutations in the β-catenin gene were not detected in 44 cases of breast carcinoma. The abnormal expression of β-catenin may be key in the carcinogenesis and progression of human breast carcinoma by upregulating the expression of cyclin D1. The abnormal expression of β-catenin, the reduced expression of axin, and the overexpression of cyclin D1 and c-myc may be useful markers for determining metastasis, providing a prognosis for human breast carcinoma and for guiding treatment.

From the radiologic pathology archives: diseases of the male breast: radiologic-pathologic correlation

Male breast disease includes a variety of benign and malignant conditions, many of which are hormonally influenced. Gynecomastia and skin lesions account for the majority of conditions in symptomatic men with a palpable abnormality, and these conditions should be accurately recognized. Imaging patterns of gynecomastia include nodular, dendritic, and diffuse patterns. Histopathologically, the nodular and dendritic patterns correlate with the florid and quiescent (fibrotic) phases of gynecomastia, respectively. The diffuse pattern may have features of both phases and is associated with exposure to exogenous estrogen. Benign-appearing palpable masses in male patients should be approached cautiously, given the overlapping morphologic features of benign and malignant tumors. In addition to gynecomastia, other benign male breast tumors include lipoma, pseudoangiomatous stromal hyperplasia, granular cell tumor, fibromatosis, myofibroblastoma, schwannoma, and hemangioma. Male breast cancer accounts for 1% of all breast carcinomas. Invasive ductal carcinoma accounts for the majority of cases in adult males and typically appears as a subareolar mass without calcifications that is eccentric to the nipple. Other epithelial and mesenchymal tumors that may occur, albeit not as commonly as in women, include papillary carcinoma, invasive lobular carcinoma, adenoid cystic carcinoma, liposarcoma, dermatofibrosarcoma, pleomorphic hyalinizing angiectatic tumor, basal cell carcinoma of the nipple, hematopoietic malignancies, and secondary tumors. Knowledge of the natural history, clinical characteristics, and imaging features of tumors that occur in the male breast will help narrow the radiologic differential diagnosis and optimize treatment.

MicroRNA-374a activates Wnt/β-catenin signaling to promote breast cancer metastasis

Tumor metastasis involves a series of biological steps during which the tumor cells acquire the ability to invade surrounding tissues and survive outside the original tumor site. During the early stages, the cancer cells undergo an epithelial-mesenchymal transition (EMT). Wnt/β-catenin signaling is known to drive EMT and metastasis. Here we report that Wnt/β-catenin signaling is hyperactivated in metastatic breast cancer cells that express microRNA 374a (miR-374a). In breast cancer cell lines, ectopic overexpression of miR-374a promoted EMT and metastasis both in vitro and in vivo. Furthermore, miR-374a directly targeted and suppressed multiple negative regulators of the Wnt/β-catenin signaling cascade, including WIF1, PTEN, and WNT5A. Notably, miR-374a was markedly upregulated in primary tumor samples from patients with distant metastases and was associated with poor metastasis-free survival. These results demonstrate that miR-374a maintains constitutively activated Wnt/β-catenin signaling and may represent a therapeutic target for early metastatic breast cancer.

Metaplastic carcinomas of the breast: diagnostic challenges and new translational insights

Comprising less than 1% of invasive carcinomas of the breast, metaplastic carcinomas are a heterogeneous group of malignant tumors in which part or all of the carcinomatous epithelium is transformed into a nonglandular (metaplastic) growth process. Metaplastic carcinomas with a low-grade spindle cell component resembling fibromatosis, as in our present case, are worthy of particular note because they are infrequent, difficult to recognize, and have a high risk of local recurrence. The differential diagnosis of metaplastic carcinomas depends on the degree of atypia observed in the tumor and includes exuberant scars, fibromatosis, nodular fasciitis, myofibroblastomas, pseudoangiomatous stromal hyperplasia, acute and chronic abscess with fat necrosis, malignant phyllodes tumor, and primary or metastatic sarcoma. Limited studies done on the molecular pathology of metaplastic carcinomas show that activation of the Wnt signaling pathway is common in these tumors and that approximately 70% of metaplastic carcinomas show EGFR gene amplification and overexpression. This may have treatment implications because they may lead to targeted treatment for patients with metaplastic carcinomas.

Important Inflammatory and Reactive Lesions of the Breast

Some inflammatory and reactive lesions of the breast present problems clinically but are treated without resort to biopsy. In others, biopsy is required to make the correct diagnosis and to distinguish the process from malignancy. Still others represent incidental microscopic findings that may create diagnostic problems. This article reviews a number of inflammatory and reactive conditions that are likely to be encountered in routine surgical pathology practice, as well as those that have been recently described.

CTNNB1 genotyping and APC screening in pediatric desmoid tumors: a proposed algorithm

Desmoid fibromatosis is a rare, locally aggressive fibroblastic/myofibroblastic tumor that occasionally involves children. We examined a series of pediatric desmoids for CTNNB1 mutations, seen in sporadic tumors, and APC germline mutations, associated with familial adenomatous polyposis (FAP). Forty-four desmoids in pediatric patients were identified in the pathology files of 2 large referral centers (1995-2009). Clinical charts were reviewed for history of FAP. Germline APC gene mutations were determined on blood samples from patients presenting with FAP. Immunohistochemistry for beta-catenin was performed. CTNNB1 genotyping was done by Sanger sequencing on formalin-fixed paraffin-embedded tissue. CTNNB1 mutations were observed in 29 of 44 (66%) desmoids, with 3 mutations identified: T41A (64%), S45F (29%), and S45P (7%). Germline APC mutations were present in 7 (16%) desmoid patients. Eight (18%) patients had desmoids that were wild type for CTNNB1 and had no known clinical signs or family history suspicious for FAP at the time of testing or with extended follow up (n  =  6). Beta-catenin nuclear labeling was observed in 38 of 41 (92%) tested cases, 34 (89%) of which showed mutations in either CTNNB1 (n  =  29) or APC (n  =  5). Nuclear localization of beta-catenin was seen in the majority of pediatric desmoids and was most often associated with somatic mutations in CTNNB1. However, a significant proportion of pediatric patients harbored germline mutations in APC. Given the implications, genetic counseling is recommended for children diagnosed with desmoid tumors lacking CTNNB1 mutations because this population is enriched for FAP patients.

Prevalence of the CTNNB1 mutation genotype in surgically resected fibromatosis of the breast

AIMS

To investigate CTNNB1 mutation and β-catenin expression in resected breast fibromatosis and to identify potential molecular markers of fibromatosis of the breast.

METHODS AND RESULTS

We selected 12 patients with fibromatosis of the breast who underwent surgical resection and were confirmed by histological examination. Ultrasonography findings for 10 patients were reviewed and only two cases were suspicious for fibromatosis on imaging. On core needle biopsy for pre-operative diagnoses, only three cases were histologically suspicious for fibromatosis. Mutations in exon 3 of CTNNB1 were detected by direct DNA sequencing in nine (75.0%) cases: all were c.121G>A (p.T41A), which was much more frequent in breast fibromatoses than in other soft tissue lesions. Nuclear β-catenin expression was observed in all cases and the level of expression was higher in cases with mutation. In eight of nine cases, the matched biopsy specimen showed the same CTNNB1 mutation status as the pre-operative specimen.

CONCLUSIONS

In the majority of cases, clinical presentation and breast imaging are highly suspicious for carcinoma. Definitive pre-operative pathological diagnosis by core needle biopsy is difficult. CTNNB1 mutation and nuclear β-catenin expression are frequently detected in sporadic breast fibromatoses, suggesting their potential as a useful tool to distinguish breast fibromatoses from other neoplasms.

Analysis of β-catenin expression and exon 3 mutations in pediatric sporadic aggressive fibromatosis

Aggressive fibromatosis is a benign tumor with a high recurrence rate after surgical resection, particularly in children. Abnormal regulation of β-catenin in the presence or absence of a change of genotype has been identified in adult sporadic aggressive fibromatosis. However, the status of β-catenin expression and mutation remains unclear in pediatric patients. The present study was designed to analyze the expression and mutation status of β-catenin in pediatric aggressive fibromatosis. B-catenin expression was analyzed by immunohistochemistry in 32 samples from pediatric patients with aggressive fibromatosis (21 recurrent cases and 11 primary-onset cases) and 15 control subjects. Somatic point mutations in β-catenin exon 3 were identified by sequencing of polymerase chain reaction products. Nuclear expression of β-catenin was detected in 94% (30/32) of aggressive fibromatosis samples and 13% (2/15) of control samples (P < 0.001). Mutations in exon 3 of the β-catenin gene were identified in 78% (25/32) of aggressive fibromatosis samples (19/21 recurrent cases, 6/11 primary-onset cases; P  =  0.032). The primary mutation in the recurrent cases occurred at codon 45 (S45F), while codon 41 (T41A) was most frequently mutated in the primary-onset cases (P  =  0.002). Abnormal expression of β-catenin appears to occur frequently in pediatric aggressive fibromatosis. Muftations in exon 3 of the β-catenin gene, particularly the S45F mutation, may represent risk factors for recurrence in pediatric patients and could potentially be used as prognostic factors.

Activation status of Wnt/ß-catenin signaling in normal and neoplastic breast tissues: relationship to HER2/neu expression in human and mouse

Wnt/ß-catenin signaling is strongly implicated in neoplasia, but the role of this pathway in human breast cancer has been controversial. Here, we examined Wnt/ß-catenin pathway activation as a function of breast cancer progression, and tested for a relationship with HER2/neu expression, using a human tissue microarray comprising benign breast tissues, ductal carcinoma in situ (DCIS), and invasive carcinomas. Cores were scored for membranous ß-catenin, a key functional component of adherens junctions, and for nucleocytoplasmic ß-catenin, a hallmark of Wnt/ß-catenin pathway activation. Only 82% of benign samples exhibited membrane-associated ß-catenin, indicating a finite frequency of false-negative staining. The frequency of membrane positivity was similar in DCIS samples, but was significantly reduced in carcinomas (45%, P<0.001), consistent with loss of adherens junctions during acquisition of invasiveness. Negative membrane status in cancers correlated with higher grade (P = 0.04) and estrogen receptor-negative status (P = 0.03), both indices of poor prognosis. Unexpectedly, a substantial frequency of nucleocytoplasmic ß-catenin was observed in benign breast tissues (36%), similar to that in carcinomas (35%). Positive-staining basal nuclei observed in benign breast may identify putative stem cells. An increased frequency of nucleocytoplasmic ß-catenin was observed in DCIS tumors (56%), suggesting that pathway activation may be an early event in human breast neoplasia. A correlation was observed between HER2/neu expression and nucleocytoplasmic ß-catenin in node-positive carcinomas (P = 0.02). Furthermore, cytoplasmic ß-catenin was detected in HER2/neu-induced mouse mammary tumors. The Axin2^NLSlacZ mouse strain, a previously validated reporter of mammary Wnt/ß-catenin signaling, was utilized to define in vivo transcriptional consequences of HER2/neu-induced ß-catenin accumulation. Discrete hyperplastic foci observed in mammary glands from bigenic MMTV/neu, Axin2^NLSlacZ mice, highlighted by robust ß-catenin/TCF signaling, likely represent the earliest stage of mammary intraepithelial neoplasia in MMTV/neu mice. Our study thus provides provocative evidence for Wnt/ß-catenin signaling as an early, HER2/neu-inducible event in breast neoplasia.

Desmoid tumour of the breast as a manifestation of Gardner's syndrome

INTRODUCTION

Desmoid tumours of the breast are rare. Although benign, they can mimic breast cancer on physical examination, mammography and breast ultrasound and can also be locally invasive. Even though they occur sporadically, they can also be seen as a part of Gardner's syndrome. We describe a case of desmoid tumour in a woman with Gardner's syndrome where the lesion was mammographically occult.

PRESENTATION OF CASE

A 63-year old woman presented with four months history of a painful left breast lump. She had a screening mammogram seven months ago which was normal. She is known to have Gardner's syndrome and had a total colectomy, she has also had multiple abdominal desmoids excised in the past. On examination there was a 4cm×5cm firm, mobile lump in the left breast. Her mammograms in the clinic were also normal. Ultrasound suggested a benign lesion of the breast and a core biopsy showed it to be a benign spindle cell lesion. She underwent wide local excision of the lump, the intraoperative mammograms of the excised specimen also failed to detect the lesion. Histopathology of the excised specimen confirmed the tumour to be a benign desmoid tumour. She has now been offered radiotherapy and nonsteriodal anti-inflammatory drugs (NSAIDs) to reduce her chances of a local recurrence.

CONCLUSION

A high index of suspicion and a thorough triple examination protocol is necessary to detect rare lesions like a desmoid tumour which can masquerade as breast carcinoma.