An immunohistochemical study of metaplastic spindle cell carcinoma, phyllodes tumor and fibromatosis of the breast

Targeted DNA Sequencing in Diagnosis of Malignant Phyllodes Tumors With Emphasis on Tumors With Keratin and p63 Expression

The differential diagnosis of malignant spindle cell neoplasms in the breast most frequently rests between malignant phyllodes tumor (MPT) and metaplastic carcinoma (MBC). Diagnosis of MPT can be challenging due to diffuse stromal overgrowth, keratin (CK) and/or p63 immunopositivity, and absent CD34 expression, which can mimic MBC, especially in core biopsies. Distinction of MPT from MBC has clinical implications, with differences in surgical approach, chemotherapy, and radiation. In this study, we evaluated MPTs (78 tumors, 64 patients) for stromal CK, p63, and CD34 expression and profiled a subset (n = 31) by targeted next-generation DNA sequencing, with comparison to MBC (n = 44). Most MPTs (71%) were CK+ and/or p63+, including 32% CK+ (25/77 focal) and 65% p63+ (32/66 focal, 10/66 patchy, and 1/66 diffuse). Thirty percent of MPTs expressed both CK and p63 (20/66), compared with 95% of MBCs (40/42, P < .001). CK and/or p63 were positive in CD34+ and CD34- MPTs. Recurrent genetic aberrations in MPTs involved TERT, TP53, MED12, CDKN2A, chromatin modifiers, growth factor receptors/ligands, and phosphoinositide-3 kinase (PI-3K) and MAPK pathway genes. Only MED12 (39%, 12/31) and SETD2 (13%, 4/31) were exclusively mutated in MPTs and not MBCs (P < .001 and P = .044, respectively), whereas PIK3R1 mutations were only found in MBCs (37%, 13/35, P < .001). Comparative literature review additionally identified ARID1B, EGFR, FLNA, NRAS, PDGFRB, RAD50, and RARA alterations enriched or exclusively in MPTs vs MBCs. MED12 was mutated in MPTs with diffuse stromal overgrowth (53%, 9/17), CD34- MPTs (41%, 7/17), and CK+ and/or p63+ MPTs (39%, 9/23), including 36% of CD34- MPTs with CK and/or p63 expression. Overall, MED12 mutation and/or CD34 expression were observed in 68% (21/31) MPTs, including 61% (14/23) of CK+ and/or p63+ tumors. Our results emphasize the prevalence of CK and p63 expression in MPTs and demonstrate the diagnostic utility of next-generation DNA sequencing, especially in MPTs with confounding factors that can mimic MBC.

Breast Cancer Histopathology in the Age of Molecular Oncology

For more than a century, microscopic histology has been the cornerstone for cancer diagnosis, and breast carcinoma is no exception. In recent years, clinical biomarkers, gene expression profiles, and other molecular tests have shown increasing utility for identifying the key biological features that guide prognosis and treatment of breast cancer. Indeed, the most common histologic pattern-invasive ductal carcinoma of no special type-provides relatively little guidance to management beyond triggering grading, biomarker testing, and clinical staging. However, many less common histologic patterns can be recognized by trained pathologists, which in many cases can be linked to characteristic biomarker and gene expression patterns, underlying mutations, prognosis, and therapy. Herein we describe more than a dozen such histomorphologic subtypes (including lobular, metaplastic, salivary analog, and several good prognosis special types of breast cancer) in the context of their molecular and clinical features.

Ultrasound characteristics of breast fibromatosis mimicking carcinoma

PURPOSE

To explore the value of ultrasound (US) characteristics in diagnosing breast fibromatosis (BF) and evaluate their differences from breast carcinoma.

METHODS

A total of 121 patients with BF (n = 24, 29 lesions) or invasive ductal carcinoma (IDC) (n = 97, 102 lesions) of the breast were included. Their clinical and US findings were recorded and analyzed.

RESULTS

The mean age of BF was younger than that of IDC (28.75 ± 5.55 vs. 50.19 ± 9.87, p < 0.001). The mean size of the BF was smaller than that of IDC (2.09 ± 0.91 vs. 2.71 ± 1.20, p = 0.011). Compared to IDC, BF had more frequency of posterior echo attenuation (p < 0.001), less frequency of peripheral hyperechoic halo (p = 0.002), calcification (p = 0.001), US reported axillary lymph node positive (p = 0.025), and grade 2-3 vascularity (p < 0.001). The Breast Imaging Reporting and Data System categorized BF at a lower level than IDC (p < 0.001). After adjusting for age, the peripheral hyperechoic halo, posterior echo feature, and vascularity could independently identify the differences between these two entities.

CONCLUSION

Some differences were observed between BF and IDC in terms of patient age, lesion size, and US characteristics.

Immunohistochemistry in the Diagnosis and Classification of Breast Tumors

CONTEXT.—

In the clinical practice of breast pathology, immunohistochemistry (IHC) of different markers is widely used for the diagnosis and classification of breast lesions.

OBJECTIVE.—

To provide an overview of currently used and recently identified IHC stains that have been implemented in the field of diagnostic breast pathology.

DATA SOURCES.—

Data were obtained from literature review and clinical experience of the authors as breast pathologists.

CONCLUSIONS.—

In the current review, we summarize the common uses of IHC stains for diagnosing different types of breast lesions, especially invasive and noninvasive breast lesions, and benign and malignant spindle cell lesions. In addition, the cutting-edge knowledge of diagnostic carcinoma markers will lead us to further understand the different types of breast carcinoma and differentiate breast carcinomas from other carcinomas of similar morphology. Knowing the strengths and limitations of these markers is essential to the clinical practice of breast pathology.

Clinical perspectives and outcomes of the giant breast phyllodes tumor and sarcoma: a real-world retrospective study

BACKGROUND

Giant breast malignant phyllodes tumor or sarcoma (GBPS) are rare entities with diameter larger than 10 cm and variously histological pleomorphisms. This disease poses a significant threat to the quality of life of individuals, and its prognosis remains unclear. This study aimed to explore the differential diagnosis, treatment, and prognosis of GBPS in a real-world retrospective cohort.

METHODS

We collected GBPS (diameter > 10 cm, n = 10) and BPS (diameter ≤ 10 cm, n = 126) from patients diagnosed with sarcoma or malignant phyllodes tumor between 2008 and 2022. We analyzed clinical characteristics, histological status, treatment, and local recurrence using the Fisher's exact test between GBPS (diameter > 10 cm) and BPS (diameter ≤ 10 cm) cohort. We described overall survival (OS) and disease-free survival (DFS) using Kaplan-Meier curves and identified risk factors for local recurrence using logistic regression. The tumor size, age at diagnosis, and differential immunohistochemistry markers of breast sarcoma or phyllodes tumor to determine the prognosis of GBPS.

RESULTS

In our retrospective analysis of breast malignancies, we identified 10 cases of GBPS and 126 cases of BPS, corresponding to a GBPS prevalence of 0.17% (10/6000). The median age was 38.5 years (inter-quartile range, IQR: 28.25-48.5 years). During the follow-up of period (median: 80.5 months, IQR: 36.75-122 months), the local recurrence (LR) rate was 40% and 20.6%, respectively. Clinical characteristics of young age (HR:2.799, 95%CI -00.09276-0.017, p < 0.05) and cytological characteristics of marked stromal atypia (HR:0.88, 95% CI 0.39-1.40, p < 0.05) were risk factors for the poor prognosis of GBPS by COX regression model analysis. The Kaplan-Meier curves of GBPS 5-year disease-free survival (DFS) and overall survival (OS) were 31.5 months and 40 months, respectively, and were not associated with adjuvant radiation or chemotherapy.

CONCLUSION

We recommend mastectomy with a clear surgical margin as the preferred treatment for GBPS. Age and stromal atypia are significantly associated with recurrence. Adjuvant radiation therapy is advised; however, there was no improvement in overall survival. There is no consensus on the effectiveness of adjuvant chemotherapy and genetic methods, highlighting the need for further research into this aggressive tumor. We recommend a multidisciplinary approach involving a dedicated team for the management of GBPS.

Fibromatosis-like metaplastic carcinoma of the breast: Two case reports

BACKGROUND

Fibromatosis-like metaplastic carcinoma is classified as a rare type of metaplastic carcinoma of the breast by the 2012 WHO pathological and genetic classification criteria for breast tumors, which takes hyperplastic spindle cells as the main component and is often misdiagnosed as benign stromal proliferative lesions or benign mesenchymal tumors of the breast because of its mild morphology. Here, we collected the clinical data of 2 cases of fibromatosis-like metaplastic carcinoma of the breast and performed pathomorphological observation and immunohistochemical staining of the surgically resected specimens. According to the clinical features, imaging features, immunophenotype, diagnosis and differential diagnosis of 2 cases of fibromatosis-like metaplastic carcinoma of the breast, it was further differentiated.

CASE SUMMARY

Case 1: A 56-year-old postmenopausal female was admitted due to "right breast mass for over 1 year and local ulceration for over 1 mo". Physical examination showed a mass with a diameter of 4.5 cm × 5.5 cm palpable at 2.5 cm from the nipple at 1 o'clock in the right breast. The skin on the surface of the mass ruptured about 3 cm, with a small amount of exudation and bleeding, less clear boundary, hard texture, fair activity, without obvious tenderness. No obvious abnormality was palpable in the left breast. No enlarged lymph nodes were palpable in the bilateral axillae and bilateral supraclavicular region. After removing the mass tissue, it was promptly sent to the pathology department for examination. Case 2: Female, 52-years-old, premenopausal, admitted due to "right breast mass for more than 3 mo". Physical examination showed a 4.0 cm × 4.0 cm diameter mass palpable at 2.0 cm of the nipple in the lower outer 7 o'clock direction of the right breast, with less clear boundary, hard texture, fair activity, no significant tenderness, no palpable significant abnormalities in the left breast, and no palpable enlarged lymph nodes in the bilateral axillae and bilateral supraclavicular region. The mass was resected and sent for pathological examination. Postoperative pathological examination revealed fibromatosis-like metaplastic carcinoma of the breast in both patient 1 and patient 2. No systemic therapy and local radiotherapy were performed after surgery, and no tumor recurrence or metastasis was observed.

CONCLUSION

Fibromatosis-like metaplastic carcinoma of the breast is a rare subtype of metaplastic carcinoma that is often misdiagnosed, and the diagnosis relies on medical history collection, complete sampling, and full use of immunohistochemical assessment. The risk of lymph node and distant metastasis is low, and the current treatment is based on complete surgical resection. The efficacy of systemic radiotherapy and chemotherapy is not clear.

Nontoxic Fluorescent Nanoprobes for Multiplexed Detection and 3D Imaging of Tumor Markers in Breast Cancer

Multiplexed fluorescent immunohistochemical analysis of breast cancer (BC) markers and high-resolution 3D immunofluorescence imaging of the tumor and its microenvironment not only facilitate making the disease prognosis and selecting effective anticancer therapy (including photodynamic therapy), but also provides information on signaling and metabolic mechanisms of carcinogenesis and helps in the search for new therapeutic targets and drugs. The characteristics of imaging nanoprobe efficiency, such as sensitivity, target affinity, depth of tissue penetration, and photostability, are determined by the properties of their components, fluorophores and capture molecules, and by the method of their conjugation. Regarding individual nanoprobe components, fluorescent nanocrystals (NCs) are widely used for optical imaging in vitro and in vivo, and single-domain antibodies (sdAbs) are well established as highly specific capture molecules in diagnostic and therapeutic applications. Moreover, the technologies of obtaining functionally active sdAb–NC conjugates with the highest possible avidity, with all sdAb molecules bound to the NC in a strictly oriented manner, provide 3D-imaging nanoprobes with strong comparative advantages. This review is aimed at highlighting the importance of an integrated approach to BC diagnosis, including the detection of biomarkers of the tumor and its microenvironment, as well as the need for their quantitative profiling and imaging of their mutual location, using advanced approaches to 3D detection in thick tissue sections. The existing approaches to 3D imaging of tumors and their microenvironment using fluorescent NCs are described, and the main comparative advantages and disadvantages of nontoxic fluorescent sdAb–NC conjugates as nanoprobes for multiplexed detection and 3D imaging of BC markers are discussed.

Fibroepithelial Lesions of the Breast: Update on Molecular Profile With Focus on Pediatric Population

CONTEXT.—

This review article derives from the breast pathology lecture at the Eighth Princeton Integrated Pathology Symposium (PIPS VIII).

OBJECTIVE.—

To provide a literature review and update on fibroepithelial lesions of the breast with molecular findings and findings regarding the pediatric population.

DATA SOURCES.—

The sources include extensive literature review, personal research, and experience.

CONCLUSIONS.—

Given significant differences in prognosis and management of fibroepithelial lesions, we aim to provide readers with pertinent definitions, pathomorphology, molecular findings, and management for each diagnosis, with insights on the pediatric population.

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.

High-Grade Spindle Cell Lesions of the Breast: Key Pathologic and Clinical Updates

Most of the high-grade spindle cell lesions of the breast are malignant phyllodes tumors (MPTs), spindle cell carcinomas (SpCCs), and matrix-producing metaplastic breast carcinomas (MP-MBCs). MPTs have neoplastic spindle stromal cells and a classic leaf-like architecture with subepithelial stromal condensation. MPTs are often positive for CD34, CD117, and bcl-2 and are associated with MED12, TERT, and RARA mutations. SpCCs and MP-MBCs are high-grade metaplastic carcinomas, whereas neoplastic epithelial cells become spindled or show heterologous mesenchymal differentiation, respectively. The expression of epithelial markers must be evaluated to make a diagnosis. SAS, or rare metastatic spindle cell tumors, are seen in the breast, and clinical history is the best supporting evidence. Surgical resection is the standard of care.

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.

Specific cell differentiation in breast cancer: a basis for histological classification

Breast parenchyma progenitor cells show a high degree of phenotypic plasticity reflected in the wide range of morphology observed in benign and malignant breast tumours. Although there is evidence suggesting that all breast cancer (BC) arises from a common epithelial progenitor or stem cell located at the terminal duct lobular units (TDLUs), BC shows a broad spectrum of morphology with extensive variation in histological type and grade. This is related to the complexity of BC carcinogenesis including initial genetic changes in the cell of origin, subsequent genetic and epigenetic alterations and reprogramming that occur at various stages of BC development and the interplay with the surrounding microenvironment, factors which influence the process of differentiation. Differentiation in BC determines the morphology, which can be measured using histological grade and tumour type. Histological grade, which measures the similarity to the TDLUs, reflects the degree of differentiation whereas tumour type reflects the type of differentiation. Understanding BC phenotypic differentiation facilitates the accurate diagnosis and histological classification of BC with corresponding clinical implications in terms of disease behaviour, prognosis and management plans. In this review, we highlight the potential pathways that BC stem cells follow resulting in the development of different histological types of BC and how knowledge of these pathways impacts our ability to classify BC in diagnostic practice. We also discuss the role of cellular differentiation in producing metaplastic and neuroendocrine carcinomas of the breast and how the latter differ from their counterparts in other organs, with emphasis on clinical relevance.

GATA binding protein 3 (GATA3) as a marker for metaplastic spindle cell carcinoma of the breast

Spindle cell lesions of the breast comprise a diverse set of tumors; harboring significant histological and immunohistochemical (IHC) overlap. Accurate diagnosis and classification of spindle cell lesions in the breast remains challenging, especially in core biopsies. In the current study, we evaluated a spectrum of spindle cell lesion of the breast with a panel of IHC antibodies in an effort to differentiate metaplastic spindle cell carcinoma from its benign and malignant mimickers. Our study included 92 patients who underwent breast core biopsies or breast resections at Northwell Health who were diagnosed with benign and malignant tumor/tumor-like spindle cell lesions. Tumors subtypes in this the study included: angiosarcoma, nodular fasciitis, fibromatosis, myofibroblastoma, phyllodes tumors (benign, borderline and malignant), primary sarcomas and metaplastic spindle cell carcinoma. Our biomarker panel included high molecular weight keratin (HMWK), CAM5.2, AE1/AE3, p63, CD34 and GATA3. GATA3 expression was significantly higher in metaplastic carcinomas (88.9 % vs 4.1 %, p < 0.001), when compared to other spindle cell lesions. The sensitivity and specificity for detecting metaplastic carcinomas reached 84.2 % and 97.3 %, respectively. Regarding cytokeratin panels, none of the three individual markers were as sensitive or specific for metaplastic breast carcinoma. GATA3 is the most specific and sensitive marker forfor the identification of metaplastic spindle cell carcinoma of the breast.

Fibroepithelial lesions revisited: implications for diagnosis and management

Fibroepithelial lesions of the breast, comprising the fibroadenoma and phyllodes tumour, are a unique group of neoplasms that share histological characteristics but possess different clinical behaviour. The fibroadenoma is the commonest benign breast tumour in women, while the phyllodes tumour is rare and may be associated with recurrences, grade progression and even metastasis. The diagnosis of fibroadenoma is usually straightforward, with recognised histological variants such as the cellular, complex, juvenile and myxoid forms. The phyllodes tumour comprises benign, borderline and malignant varieties, graded using a constellation of histological parameters based on stromal characteristics of hypercellularity, atypia, mitoses, overgrowth and the nature of tumour borders. While phyllodes tumour grade correlates with clinical behaviour, interobserver variability in assessing multiple parameters that are potentially of different biological weightage leads to significant challenges in accurate grade determination and consequently therapy. Differential diagnostic considerations along the spectrum of fibroepithelial tumours can be problematic in routine practice. Recent discoveries of the molecular underpinnings of these tumours may have diagnostic, prognostic and therapeutic implications.

Metaplastic carcinomas of the breast without evidence of epithelial differentiation: a diagnostic approach for management

AIMS

Although rare, malignant sarcomatoid breast tumours without evidence of epithelial differentiation comprise a diagnostic challenge with management implications. Earlier studies have generally considered these to be primary breast sarcomas; however, supporting evidence is lacking and management remains variable. This study aimed to provide an evidence-based approach to improve the consistency of diagnosis and management for such cases.

METHODS AND RESULTS

A large series (n = 140) of metaplastic breast carcinoma (MBC) diagnosed in Nottingham over 18 years was analysed. Only cases with available data on immunohistochemical expression of cytokeratins (CKs) were included. The prevalence and pattern of expression for various CKs were assessed and details of tumours negative for CKs were collected. A diagnostic approach based on our experience is provided. Forty-seven cases (34%) showed foci of conventional type invasive breast carcinoma or ductal carcinoma in situ (DCIS), while 93 cases (66%) were diagnosed as MBC based on morphology and/or CK expression. Ninety-seven cases (69%) were negative for one or more CKs, with 18 cases (13%) negative for five or more CKs. Eight cases (6%) lacked expression of all CKs tested. Further examination showed evidence of carcinomatous nature in five cases, and three were diagnosed as MBC following extensive diagnostic work-up and based on our experience.

CONCLUSION

This study suggests that MBC represents a spectrum of neoplasms, with some lacking CK expression. Sarcomatoid neoplasms of the breast lacking evidence of carcinomatous morphology and CK expression may represent an extreme end of differentiation that can be considered as carcinomas rather than sarcomas for management purposes (following extensive work-up).

Core needle biopsy diagnosis of fibroepithelial lesions of the breast: a diagnostic challenge

Fibroepithelial lesions (FEL) of the breast are biphasic neoplasms consisting of proliferative epithelial and stromal components and include fibroadenoma, phyllodes tumour and periductal stromal tumour. Core needle biopsy (CNB) is a commonly used diagnostic modality for investigation of breast lesions. As the accurate diagnosis of FEL requires integrated assessment of both epithelial and stromal components, this may create problems in small biopsies with limited sampling. In this review, common problems encountered in CNB of FEL are discussed, including establishing a diagnosis of borderline/malignant phyllodes tumour in a biopsy consisting of malignant spindle cells, differentiating phyllodes tumour from fibroadenoma on CNB, grading of phyllodes tumour of intermediate histological grade and assessment of periductal stromal tumours. The approaches are detailed systematically based on histology, immunohistochemistry and molecular characterisation. This comprehensive approach may aid in dealing with the overlapping histological appearance of FEL and sampling limitations of CNB.

Breast fibromatosis: Imaging and clinical findings

Breast fibromatosis is a rare histologically benign tumor with local aggressive potential, and imaging and clinical findings of breast fibromatosis require attention. We retrospectively evaluated the images of 20 patients with histologically proven breast fibromatosis on mammography, magnetic resonance imaging (MRI), and ultrasonography. The lesions were assessed concerning the location, fascia involvement, imaging characteristics, and follow-up outcomes. Altogether, there were 22 lesions: 10 lesions involved the superficial fascia system including four lesions additionally involving the deep fascia and pectoralis major, and 12 lesions were inside the glandular parenchyma with two lesions originated from the prior surgery site. The detection rates of mammography, ultrasound, and MRI for breast fibromatosis were 33.3% (3/9), 90% (18/20), and 100% (3/3), respectively. We found that fascia involvement may be a characteristic of breast fibromatosis. The lesion located inside glandular parenchyma is prone to be underestimated, whereas combined MR with ultrasound is recommended for the diagnosis. The complete excision with negative margins is important for a good prognosis.

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.

Immunohistochemistry for diagnosis and prognosis of breast cancer: a review

Breast cancer is the most prevalent malignant tumor and main oncologic cause of mortality in women. Although most diagnosis of breast pathology is accomplished using hematoxylin and eosin stained sections, some cases require immunohistochemistry for proper evaluation. We investigated the latter cases including distinctions between ductal and lobular carcinoma, in situ and invasive carcinoma, typical ductal hyperplasia and atypical ductal hyperplasia/ductal carcinoma in situ, papillary and spindle cell lesion assessment, metastasis evaluation, and assessment of prognostic and therapy markers. E-cadherin is used to differentiate ductal and lobular carcinoma; 34βE12, CK8, p120 catenin and β-catenin also produce consistent results. Myoepithelial cell (MEC) stains are used to evaluate in situ and invasive carcinoma; calponin, smooth muscle myosin heavy chain and p63 are sensitive/specific markers. 34βE12 and CK5/6 are positive in ductal hyperplasia, which enables its differentiation from atypical ductal hyperplasia and ductal carcinoma in situ. CK 5/6, ER and MEC markers are consistent options for evaluating papillary lesions. Spindle cell lesions can be assessed using β-catenin, SMA, CD34, p63, CKs and hormone receptors. It is important to differentiate primary carcinomas from metastases; the most commonly used markers to identify breast origin include mammaglobin, GCDFP-15, GATA3 and ER, although none of these is completely sensitive or specific. Immunohistochemistry can be used to evaluate central prognostic and predictive factors including molecular subtypes, HER2, hormone receptors, proliferation markers (Ki-67) and lymph-vascular invasion markers including ERG, CD31, CD34, factor VIII and podoplanin. Owing to the complexity of mammary lesions, diagnosis also depends on each particular situation, evaluation of cytological characteristics revealed by immunochemistry and correlation with histological findings.

Accuracy and clinical implications of pre-operative breast core needle biopsy diagnoses of fibroepithelial neoplasms and sarcomatoid carcinomas

PURPOSE

Accurate classification of breast phyllodes tumors (PTs) on core biopsy can be challenging. The differential diagnosis of benign PT (BP) is fibroadenoma (FA), whereas the differential diagnosis of malignant PT (MP) is sarcomatoid (metaplastic) carcinoma (SC).

METHODS

Here, we compare the pre-excision core biopsy diagnosis and clinicopathologic features of histologically confirmed MP, borderline PT (BLP), BP, FA, and SC. Consecutive cases of 34 histologically confirmed PT (14 MP, 10 BLP, 10 BP), 13 SC, and 10 FA were identified.

RESULTS

A core biopsy diagnosis of SC was made only in SC (77%, p = 0.003). The diagnosis "malignant neoplasm" or "atypical spindle cell neoplasm" was made in 100% MP and 23% SC, but no other tumor (p = 0.0001). The diagnosis "phyllodes tumor" was made only in PT (44% BLP, 11% BP, p = 0.06). The diagnosis "fibroepithelial lesion" was made in 44% BLP, 67% BP, and 29% FA. The diagnosis "FA" was made most commonly in FA (57%) (versus 22% BP and no other tumor; p = 0.002). Neoadjuvant therapy was given only in SC (23%, p = 0.03); adjuvant therapy was given in 46% SC and 13% MP (p = 0.04).

CONCLUSIONS

A pre-operative core biopsy diagnosis of "malignant spindle cell neoplasm" separates MP and SC from BLP, BP, and FA. However, MP and SC can have overlapping features on core biopsy. Thus, one must be careful not to overcall SC on core biopsy, as patients diagnosed with SC may receive neoadjuvant therapy. A core biopsy diagnosis of "phyllodes tumor" is specific for PT and can guide treatment planning of a wide local excision.

Primary Breast Atypical Lipomatous Tumor/ Well-Differentiated Liposarcoma and Dedifferentiated Liposarcoma

Atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) and its higher-grade counterpart, dedifferentiated liposarcoma (DDL), are extraordinarily rare tumors in the breast. The main differential diagnostic consideration of primary breast ALT/WDL is malignant phyllodes tumor with liposarcomatous differentiation, and the main differential diagnostic consideration of DDL in the breast is metaplastic breast carcinoma, particularly the spindle cell type, with heterologous sarcomatous differentiation. These differential diagnoses may be particularly challenging when evaluating limited core needle biopsy sampling. MDM2 and/or CDK4 protein overexpression and gene amplification are beneficial ancillary studies that can help establish the diagnosis of primary breast ALT/WDL and DDL, and effectively rule out the diagnoses of malignant phyllodes tumor and metaplastic breast carcinoma.

Phyllodes Tumor with Osteosarcomatous Differentiation: A Comparative Immunohistochemical Study between Epithelial and Mesenchymal Cells

Aims and background

Phyllodes tumor of the breast with osteosarcomatous differentiation is rare and very little is known about its molecular profile.

Methods and study design

An immunohistochemical panel with 37 primary antibodies including cytokeratins, mesenchymal markers, key regulators of the cell cycle, oncogenes, apoptosis-related proteins, metalloproteinases and their inhibitors was performed on a formalin-fixed paraffin-embedded sample of phyllodes tumor with osteosarcomatous differentiation in a 49-year-old woman.

Results

Antiapoptotic stimuli (survivin) predominated in sarcomatous cells. Antiproteolytic stimuli (TIMP-1, TIMP-2 and PAI) were preponderant in all cells, a surprising fact in view of the aggressiveness of the neoplasm. The immunoprofile of the osteoblastic and stromal cells was quite similar, except for c-erbB-3, c-myc, cyclin D1 and p21. Both exhibited positive cells for actin, MyoD1 and GFAP.

Conclusions

Our results suggest that this osteosarcoma may have originated from metaplasia of stromal cells that underwent a malignant change.

Rare variant of metaplastic carcinoma of the breast: a case report and review of the literature

Background

Metaplastic carcinoma encompasses a group of neoplasms characterized by differentiation of the neoplastic epithelium into squamous cells and/or mesenchymal-looking elements. Spindle cell carcinoma is a rare variant of this special histological type. Its prognosis remains poor, with a high rate of local recurrence and distant metastasis. To date, only a small number of cases have been described. There is no clear agreement on this histological subtype.

Case presentation

We report a case of a 53-year-old Moroccan woman who consulted our institution following palpation of a nodule of the left breast. Mammography in combination with breast ultrasonography revealed a lesion classified as Breast Imaging Reporting and Data System 4 with microcalcification. The patient was diagnosed with spindle cell carcinoma of the breast. The diagnosis was based primarily on histological and immunohistochemical studies of the breast biopsy and secondarily on the surgical specimen. No local or distant metastasis was found. The treatment used was total surgical excision followed by radiotherapy.

Conclusions

We describe the features (epidemiological, clinical, histological, immunohistochemical, and therapeutic outcomes) of our patient’s case and compare them with literature data.

A Diagnostic Approach to Fibroepithelial Breast Lesions

Fibroepithelial breast lesions encompass a heterogeneous group of neoplasms that range from benign to malignant, each exhibiting differing degrees of stromal proliferation in relation to the epithelial compartment. Fibroadenomas are common benign neoplasms that may be treated conservatively. Phyllodes tumors are relatively rare lesions, and classified as benign, borderline, or malignant based on histologic evaluation of various parameters. The diagnostic interpretation of "gray-zone" fibroepithelial lesions often imposes formidable demands on a pathologist's skills. This article offers practical recommendations for the diagnostic workup of these lesions, including the appropriate utilization of ancillary investigations and the approach to core needle biopsies.

Fibromatosis of the Breast: Diagnostic Accuracy of Core Needle Biopsy

OBJECTIVES

Fibromatosis of the breast is an uncommon neoplasm with potential for local recurrence. Treatment has traditionally been surgical excision with current trends toward conservative management. Given the option of observation after diagnosis by core needle biopsy (CNB), we sought to evaluate the accuracy of CNB for diagnosing fibromatosis.

METHODS

We identified a total of 31 cases in which fibromatosis had been diagnosed or included in the differential diagnosis on a CNB, an excision, or both. Morphology and immunohistochemical results were reviewed.

RESULTS

Aberrant nuclear immunoreactivity for β-catenin and absent staining for CD34 were the most useful studies to diagnose fibromatosis, and one or both were performed in 21 (68%) cases. High molecular weight cytokeratins and p63 were helpful to exclude spindle cell carcinoma. Of 26 cases confirmed as fibromatosis on excision, 22 (85%) were diagnosed as fibromatosis or fibromatosis was favored in the differential diagnosis on CNB. More frequent use of immunohistochemistry would likely have resulted in a greater number of definitive diagnoses. Fibromatosis was rarely mistaken for other nonmalignant stromal lesions, with no cases misdiagnosed as carcinoma.

CONCLUSIONS

CNB can be an accurate method of diagnosing fibromatosis, allowing observation for a select group of patients.

Diagnosis of Metaplastic Breast Carcinoma: Keratin OSCAR Versus Other Cytokeratins

Metaplastic breast carcinoma (MBC) is a heterogenous group of tumors that diverge from conventional glandular differentiation. The metaplastic component can be focal or may be present purely posing diagnostic challenges. Since MBC may show focal immunostaining or may even be negative for some cytokeratins (CK), different CKs are often needed to prove their epithelial origin. OSCAR is a relatively new broad-spectrum anti-CK antibody. Thirty MBC cases diagnosed at our institution were retrieved, including 7 spindle cell carcinomas. Representative slides were immunostained for CK-OSCAR, CK-AE1/AE3, CAM5.2, CK-903, and CK5/6. Nineteen spindle cell lesions were used as controls, including 6 malignant and 10 borderline phyllodes tumor, 1 inflammatory pseudotumor, 1 solitary fibrous tumor, and 1 nodular fasciitis case. All 30 cases (100%) of metaplastic carcinomas were positive for CK-OSCAR, compared with 27/30 (90%, P=0.076) for CK-AE1/AE3, 21/30 (70%, P≤0.01) for CK-903, 19/30 (63.3%, P≤0.01) for CAM5.2, and 15/30 (50%, P≤0.01) for CK5/6. All control cases were negative for CK-OSCAR. All 7 spindle cell carcinomas were also positive for CK-OSCAR (100%) compared with 6/7 (85.7%) for CK-AE1/AE3, 4/7 (57%) for CK-903, 3/7 (42.8%) for CAM5.2, and 2/7 (28.5%) for CK5/6. Our data show that CK-OSCAR is more sensitive than other individual CKs in diagnosing MBC. Coupled with high specificity, CK-OSCAR may potentially be used in lieu of a panel of CKs to identify the epithelial origin of these tumors, especially in spindle cell tumors. This is particularly useful in limited core biopsy specimens, to help guide treatment and simultaneously lower testing costs.

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.

Fibroepithelial lesions; The WHO spectrum

Fibroepithelial lesions of the breast comprise a morphologically and biologically heterogeneous group of biphasic tumors with epithelial and stromal components that demonstrate widely variable clinical behavior. Fibroadenomas are common benign tumors with a number of histologic variants, most of which pose no diagnostic challenge. Cellular and juvenile fibroadenomas can have overlapping features with phyllodes tumors and should be recognized. Phyllodes tumors constitute a spectrum of lesions with varying clinical behavior and are graded as benign, borderline or malignant based on a set of histologic features according to recommendations by the World Health Organization (WHO). Recent developments have significantly expanded our understanding of the pathogenesis of fibroepithelial lesions, highlighting fibroadenomas as true neoplasms and underscoring a commonality with phyllodes tumors in the form of recurrent MED12 exon 2 mutations. In addition, sequencing studies have elucidated pathways associated with phyllodes tumor progression. Accurate diagnosis and grading of phyllodes tumors are important for patient management and prognosis, as grade broadly correlates with increasing local recurrence risk, and essentially only malignant tumors metastasize. However, classification of fibroepithelial lesions in many cases remains challenging on both core biopsy and excision specimens. A commonly encountered problem at the benign end of the spectrum is the distinction of benign phyllodes tumor from cellular fibroadenoma, which is largely due to the subjective nature of histologic features used in diagnosis and histologic overlap between lesions. Grading is further complicated by the requirement to integrate multiple subjective and ill-defined parameters. On the opposite end of the histologic spectrum, malignant phyllodes tumors must be distinguished from more common metaplastic carcinomas and from primary or metastatic sarcomas, which can be especially difficult in core biopsies. Immunohistochemistry can be useful in the differential diagnosis but should be interpreted with attention to caveats. This review provides an overview and update on the spectrum of fibroepithelial lesions, with special emphasis on common problems and practical issues in diagnosis.

Phyllodes Tumor of the Breast: Histopathologic Features, Differential Diagnosis, and Molecular/Genetic Updates

CONTEXT

-Phyllodes tumor (PT) of the breast is a rare fibroepithelial neoplasm with risks of local recurrence and uncommon metastases. The classification proposed by the World Health Organization for PTs into benign, borderline, and malignant is based on a combination of several histologic features. The differential diagnosis between PT and fibroadenoma and the histologic grading of PT remain challenging. In addition, the molecular pathogenesis of PT is largely unknown.

OBJECTIVE

-To provide an updated overview of pathologic features, diagnostic terminology, and molecular alterations of PT.

DATA SOURCES

-Current English literature related to PT of the breast.

CONCLUSIONS

-Phyllodes tumor shows a wide spectrum of morphology. There are no clearly distinct boundaries between PT and fibroadenoma. Strict histologic assessment of a combination of histologic features with classification can help to achieve the correct diagnosis and provide useful clinical information. The genomic landscapes of PT generated from genomic sequencing provide insights into the molecular pathogenesis of PT and help to improve diagnostic accuracy and identify potential drug targets in malignant PT.

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.

The Expression of p63 and Cytokeratin 5 in Mixed Tumors of the Canine Mammary Gland Provides New Insights into the Histogenesis of These Neoplasms

Cytokeratin 5 and p63 have been described as basal and myoepithelial cell markers in human breast. Mixed tumors of the canine mammary gland have been associated with a myoepithelial origin. Cytokeratin 5 expression has not been evaluated in these tumors. We investigated the relation between cytokeratin 5 and p63 double-immunohistochemical expression in 23 mixed tumors of the canine mammary gland (10 benign mixed tumors and 13 carcinomas arising from benign mixed tumors) and their origin. Cytokeratin 5 and p63 co-expression was observed in myoepithelial cells of benign mixed tumors, as well as in squamous differentiation of carcinoma arising from benign mixed tumors. Though a few interstitial spindle cells of the mesenchymal components expressed both p63 and cytokeratin 5, the basal epithelial cells were labeled only by cytokeratin 5. The co-expression of p63 and cytokeratin 5 in myoepithelial cells and squamous differentiation suggest that, like in human breast, cytokeratin 5 can also be considered a myoepithelial- and squamous-cell differentiating marker in canine tumors. The presence of some interstitial spindle cells stained for p63 and cytokeratin 5 might be associated with a myoepithelial origin of the mesenchymal component of mixed tumors of the canine mammary gland. Moreover, contrary to p63, basal epithelial cells were labeled by cytokeratin 5, indicating that cytokeratin 5 may not represent an exclusive myoepithelial cell marker but also a basal epithelial cell marker in canine mixed tumors. According to these data, basal epithelial cells may be related to the origin of the epithelial component of mixed tumors of the canine mammary gland.

Use of Immunohistochemical Stains in Epithelial Lesions of the Breast

BACKGROUND

During the last few decades, immunohistochemistry (IHC) has become an integral part of pathology. Although hematoxylin and eosin (H & E) stain remains the fundamental basis for diagnostic pathology of the breast, IHC stains provide useful and sometimes vital information. Moreover, considering the role of hormonal therapy in hormone receptor-positive breast tumors, as well as the availability of targeted chemotherapeutic agents for HER2-positive cases, IHC studies represent a major part of workups.

METHODS

A literature search was performed to explore the uses of IHC stains related to the diagnoses of breast lesions and prognostic/predictive information.

RESULTS

Selective use of IHC stains in conjunction with H & E examination helps resolve most diagnostic issues encountered by surgical pathologists during their day-to-day practice. Pathologists should be familiar with the use of each immunostain and its limitations to avoid interpretative errors.

CONCLUSIONS

IHC stains help guide the differential diagnosis of challenging epithelial lesions of the breast. They should be selectively and judiciously used and their findings must be interpreted with the differential diagnoses in mind and with an understanding of possible pitfalls.

Phyllodes tumours of the breast: a consensus review

Phyllodes tumours constitute an uncommon but complex group of mammary fibroepithelial lesions. Accurate and reproducible grading of these tumours has long been challenging, owing to the need to assess multiple stratified histological parameters, which may be weighted differently by individual pathologists. Distinction of benign phyllodes tumours from cellular fibroadenomas is fraught with difficulty, due to overlapping microscopic features. Similarly, separation of the malignant phyllodes tumour from spindle cell metaplastic carcinoma and primary breast sarcoma can be problematic. Phyllodes tumours are treated by surgical excision. However, there is no consensus on the definition of an appropriate surgical margin to ensure completeness of excision and reduction of recurrence risk. Interpretive subjectivity, overlapping histological diagnostic criteria, suboptimal correlation between histological classification and clinical behaviour and the lack of robust molecular predictors of outcome make further investigation of the pathogenesis of these fascinating tumours a matter of active research. This review consolidates the current understanding of their pathobiology and clinical behaviour, and includes proposals for a rational approach to the classification and management of phyllodes tumours.

Expression of p40 and laminin 332 in metaplastic spindle cell carcinoma of the breast compared with other malignant spindle cell tumours

AIMS

To determine the use of p40 and laminin 332 (LN332) immunostains for diagnosing metaplastic carcinoma by studying the expression of these and other routine markers in spindle cell metaplastic carcinomas and other malignant spindle cell tumours.

METHODS

We identified cases of spindle cell metaplastic carcinoma (n=36) and other atypical/malignant spindle cell tumours, including 20 phyllodes tumours (14 borderline, six malignant) and 23 spindle cell sarcomas (three primary to breast). Immunohistochemical staining was performed for p40 and two LN332 chains, β3 (kalinin B1) and γ2 (lamC2). The expression of these markers was compared with p63 and cytokeratins.

RESULTS

p40 and p63 expression was seen in 21 of 36 (58.3%) and 33 of 36 (91.7%) metaplastic carcinomas, respectively. No phyllodes tumours showed stromal expression of p40 or p63. One of 23 (4.3%) sarcomas showed focal weak p63 staining. LamC2 and kalinin B1 expression was seen in 28 of 36 (77.8%) and 26 of 36 (72.2%) metaplastic carcinomas, respectively. LamC2 and kalinin B1 each showed positive stromal cell expression in two of 20 (10%) phyllodes tumours. No sarcomas showed staining with lamC2. Kalinin B1 staining was seen in 17 of 23 (73.9%) sarcomas, including two of three primary breast sarcomas. Cytokeratin expression was seen in 32 of 36 (88.9%) metaplastic carcinomas and diffuse staining was most often seen in 34βE12 and CK5.

CONCLUSIONS

The diagnostic value of relatively novel markers p40 and LN332 was found to be less than that of routinely used markers (p63 and cytokeratins). p40 proved to be a specific marker but lacked the sensitivity of p63, while LN332 showed staining in a significant proportion of phyllodes tumours and sarcomas.

Keratin Expression Patterns in Stromal Cells of Benign Sclerosing Lesions of the Breast: A Potential Diagnostic Pitfall

Context

Metaplastic carcinomas arising in association with benign sclerosing lesions (BSLs) are rare malignancies in which a neoplastic spindle cell proliferation can be recognized extending beyond the boundaries of the complex sclerosing lesion or papilloma. However, in cases in which the metaplastic carcinoma is of the low-grade fibromatosis-like type or is a low-grade adenosquamous carcinoma, distinction from the background BSL can be a significant challenge. Cytokeratin (CK) and/or p63 immunostains are helpful in confirming the diagnosis of metaplastic carcinoma, but the expression patterns of these markers in the stromal cells of BSLs have not been well characterized.

Objective

To characterize the expression patterns of CKs and p63 in BSLs.

Design

We evaluated the spindle cell component of 55 BSLs using CK 5/6, CK 903, CK MNF116, and p63.

Results

A total of 45 cases (81%) showed no staining for CKs or p63 in benign stromal cells. CK 5/6, CK 903, and p63 were positive in one case each. CK MNF116 stained spindle cells within 10 BSLs. No cases showed spindle cell reactivity for all 4 markers. Positive cases demonstrated very focal, weak staining of spindle cells; only 1 case showed focal, moderate CK staining. Spindle cell positivity was not associated with lesion type, growth pattern, spindle cell atypia, or mitoses.

Conclusions

These findings suggest that although the presence or absence of expression of CK 5/6, CK 903, and p63 may be useful to distinguish BSL from metaplastic carcinomas arising in this setting, CK MNF116 positivity may be a diagnostic pitfall.

Low-Grade Fibromatosis-like Spindle Cell Carcinoma of the Breast

Low-grade fibromatosis-like spindle cell carcinoma is a rare tumor in the breast, and represents a variant of the very heterogeneous group of metaplastic carcinomas of the breast. These tumors warrant distinction because of their resemblance to pure fibromatosis, their propensity for local recurrence, and their favorable prognosis among the metaplastic carcinomas of the breast. The diagnosis is potentially challenging, particularly on core needle biopsies, because of the morphologic overlap with other low-grade spindle cell lesions. Recognition of a proliferation of cytologically bland spindle cells with areas of epithelial differentiation in combination with immunohistochemistry using antibodies against cytokeratins and myoepithelial markers should aid in producing a definitive diagnosis. These tumors can be locally aggressive with an increased incidence of local recurrence, but the potential for lymph node or distant metastasis is low. Complete excision with adequate margins is considered curative in the majority of cases.

Application of immunohistochemistry in breast pathology: a review and update

CONTEXT

Immunohistochemistry is a valuable tool in routine breast pathology, used for both diagnostic and prognostic parameters. The diagnostic immunomarkers are the scope of this review. Most breast lesions can be diagnosed on routine hematoxylin-eosin sections; however, in several scenarios, such as morphologically equivocal cases or metastatic tumors of unknown primary, the appropriate application of immunohistochemistry adds true value in reaching an accurate diagnosis.

OBJECTIVE

To evaluate the diagnostic utility of the most commonly studied immunomarkers in the field of breast pathology by review of the literature, using the database of indexed articles in PubMed (US National Library of Medicine, Bethesda, Maryland) from 1976 to 2013.

DATA SOURCES

Literature review, and author's research data and personal practice experience.

CONCLUSIONS

The appropriate use of immunohistochemistry by applying a panel of immunomarkers and using a standardized technical and interpretational method will complement the morphologic assessment and aid in the accurate classification of difficult breast lesions and the identification of metastasis from a breast primary.

A subset of malignant phyllodes tumors express p63 and p40: a diagnostic pitfall in breast core needle biopsies

Breast phyllodes tumors are rare fibroepithelial neoplasms of variable grade, and one key differential of malignant phyllodes on core biopsy is sarcomatoid carcinoma. p63 is reported to be sensitive and specific for sarcomatoid carcinoma, with rare expression in phyllodes in limited series. The p63 deltaNp63 isoform, p40, is postulated to be more specific for squamous differentiation but has not previously been evaluated in breast phyllodes or sarcomatoid carcinoma. Tissue microarrays containing 34 unambiguous phyllodes tumors (10 benign, 10 borderline, 14 malignant), 13 sarcomatoid carcinomas, and 10 fibroadenomas were labeled by immunohistochemistry for p63, p40, CD34, and cytokeratins AE1/AE3, 34betaE12, and CK8/18. No borderline phyllodes tumor, benign phyllodes tumor, or fibroadenoma labeled with p63, p40, or cytokeratin. However, p63 labeled 57% malignant phyllodes tumors and 62% sarcomatoid carcinomas, and p40 labeled 29% malignant phyllodes (focal) and 46% sarcomatoid carcinomas. Among established markers, cytokeratins labeled 21% malignant phyllodes tumors (focal) and 100% sarcomatoid carcinomas. CD34 labeled 57% malignant phyllodes tumors and no sarcomatoid carcinomas. Focal p63, p40, and cytokeratin labeling can be seen in malignant phyllodes tumors but not in lower-grade fibroepithelial lesions, and immunoreactivity with these markers alone is not diagnostic of sarcomatoid carcinoma on core needle biopsy. In the differential diagnosis of malignant phyllodes, p40 is a more specific but less sensitive marker of sarcomatoid carcinoma than p63. These results are consistent with the sarcoma literature in which p63 labeling has been increasingly reported and suggest caution in classifying malignant spindle cell tumors of the breast on core biopsy.

Benign phyllodes tumor of the breast recurring as a malignant phyllodes tumor and spindle cell metaplastic carcinoma

We report a unique case of a 59-year-old woman diagnosed with a benign phyllodes tumor (PT), which recurred twice in the same location over a 7-year period: first as a malignant PT and then as a malignant PT with coexisting spindle cell metaplastic breast carcinoma (MBC). The MBC was differentiated from the malignant PT by expression of cytokeratins (CKs) AE1/AE3, CK MNF-116, CK 5/6, and p63. Somatic mutation analysis using a next-generation sequencing platform revealed a shared mutation in F-box and WD repeat domain containing 7, a tumor suppressor gene that encodes a ubiquitin ligase-associated protein, in the original benign PT and the first recurrent malignant PT. Chromosomal microarray analysis showed shared genetic gains and losses between the malignant PT and MBC. This case highlights the utility of immunohistochemistry to differentiate malignant PT from spindle cell MBC, describes a novel mutation in PT, and demonstrates a biologic relationship between these 2 entities.

Metaplastic carcinoma of the breast: an immunohistochemical study

Background

Metaplastic breast carcinoma is a rare entity of breast cancer expressing epithelial and/or mesenchymal tissue within the same tumor. The aim of this study is to evaluate the clinicopathological features of metaplastic breast carcinoma and to confirm the triple negative, basal-like and/or luminal phenotype of this type of tumor by using immunohistochemical staining.

Methods

Seven cases of MBC were evaluated for clinico-pathological features including follow up data. Cases were studied immunohistochemically by CK-Pan, Vimentin, ER, PR, HER2, basal markers (CK5/6, p63, EGFR, SMA and S-100), luminal cytokeratins (CK8, CK18 and CK19), markers for syncytial cells (β-HCG and PLAP), as well as prognostic markers (p53, ki-67 and calretinin).

Results

The mean age of the patients was 36 years. Three cases showed choriocarcinomatous features. All of our cases were negative for ER, PR and HER2. Six out of the 7 cases showed basal-like differentiation by demonstrating positivity with at least one of the basal/myoepithelial markers. Also 6 out of the 7 cases expressed luminal type cytokeratins (CK8, CK18 and/or CK19). P53 was positive in 3 cases, ki-67 was strongly expressed in only one case, while calretinin was expressed in 6 cases.

Conclusion

Metaplastic breast carcinoma presents in our population at a younger age group than other international studies. All cases are categorized immunohistochemically under the triple negative group of breast cancer and 86% of them exhibited basal-like and luminal phenotype. Majority of cases developed local recurrence and distant metastasis in a relatively short period of time.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1101289295115804

Fibromatosis-like metaplastic carcinoma of the breast has a claudin-low immunohistochemical phenotype

Fibromatosis-like metaplastic carcinoma (FLMCa) of the breast is a rare low-grade spindle cell carcinoma, of which the biological characteristics have not been well studied. This study aims to assess, in FLMCa, immunohistochemical expression of claudins (CLDN) and features connected with the claudin-low subtype, such as the presence of tumor initiating cells (TIC), epithelial-mesenchymal transition (EMT) phenotype, as well as EGFR activating mutations. Three cases of FLMCa were retrieved from our hospital archives. Histological and immunohistochemical characteristics were reviewed. Expression of CLDN-1, CLDN-3, CLDN-4 and CLDN-7, CD44 and CD24 (TIC phenotype), and vimentin and E-cadherin (EMT features) were studied. EGFR mutations on exons 18, 19, 20, and 21 were investigated by real-time PCR. In all cases, the low-grade spindle cell component was predominant, with two cases presenting <5 % of epithelioid and squamous areas. The tumors expressed basal cytokeratins and vimentin and were hormone receptor and ERBB2 negative. CLDN membrane expression was negative in the spindle cell component. The epithelioid areas were CLDN-1 positive. Nuclear/cytoplasmatic expression of CLDN-4 was observed in all components, except in one case in which it was strongly expressed in the non-spindle areas. All three cases were CD44+/CD24-. E-cadherin was focally expressed in epithelioid cells, only in the squamous areas. Activating EGFR mutations were not found. One patient developed local recurrences, metastases and died. FLMCa have the immunohistochemical profile of claudin-low breast tumors, with low expression of adhesion molecules, presence of TIC and EMT phenotype. No EGFR activating mutations were found.

Fibroepithelial tumors of the breast: pathologic and immunohistochemical features and molecular mechanisms

CONTEXT

The 2 main prototypes of fibroepithelial tumors of the breast include fibroadenoma and phyllodes tumor (PT). Although both tumors share some overlapping histologic features, there are significant differences in their clinical behavior and management. Phyllodes tumors have been further divided into clinically relevant subtypes, and there is more than one classification scheme for PT currently in use, suggesting a lack of consistency within different practices. Accurate differentiation between fibroadenoma and PT, as well as the grading of PT, may sometimes be challenging on preoperative core needle biopsy. Some immunohistochemical markers have been suggested to aid in the pathologic classification of these lesions.

OBJECTIVE

To discuss the salient histopathologic features of fibroepithelial tumors and review the molecular pathways proposed for the initiation, progression, and metastasis of PTs. Also, to provide an update on immunohistochemical markers that may be useful in their differential diagnosis and outline the practice and experience at our institution from a pathologic perspective.

DATA SOURCES

Sources included published articles from peer-reviewed journals in PubMed (US National Library of Medicine).

CONCLUSIONS

Fibroepithelial tumor of the breast is a heterogenous group of lesions ranging from fibroadenoma at the benign end of the spectrum to malignant PT. There are overlapping histologic features among various subtypes, and transformation and progression to a more malignant phenotype may also occur. Given the significant clinical differences within various subtypes, accurate pathologic classification is important for appropriate management. Although some immunohistochemical markers may be useful in this differential diagnosis, histomorphology still remains the gold standard.

Metaplastic breast cancer: histologic characteristics, prognostic factors and systemic treatment strategies

Metaplastic breast cancer (MBC) is a rare subtype of invasive breast cancer that tends to have an aggressive clinical presentation as well as a variety of distinct histologic designations. Few systemic treatment options are available for MBC, as it has consistently shown a suboptimal response to standard chemotherapy regimens. These characteristics result in a worse overall prognosis for patients with MBC compared to those with standard invasive breast cancer. Due to its rarity, data focusing on MBC is limited. This review will discuss the clinical presentation, breast imaging findings, histologic and molecular characteristics of MBC as well as potential future research directions.