Accuracy and Comparison of Core Needle Biopsy Diagnoses With Excision Specimen for Diagnosing Fibroepithelial Lesions of the Breast.

Background Core needle biopsy (CNB) for fibroepithelial lesions (FELs) of the breast is commonly encountered by histopathologists. The distinction between fibroadenoma (FA) and phyllodes tumor (PT) can be challenging due to overlapping histological features and the limited nature of CNB material.  Objective This study aimed to assess the accuracy of CNB diagnosis of FA and PT by comparing it with a diagnosis on subsequent surgical excision specimen. Materials and methods A total of 166 cases of FELs of the breast who underwent CNB and subsequent surgical excision between January 2001 and December 2020 were included in our study. All microscopy glass slides were reviewed, and diagnosis confirmed. Results While 125 (75%) cases based on CNB received a definitive diagnosis of either fibroadenoma or PT, the remaining 41 (25%) cases were better classified on excision specimens and were descriptively diagnosed as fibroepithelial lesions on CNB. Diagnoses on CNB and on subsequent excision specimens were concordant in 113 (90.4%) cases. Among 12 cases that were discordant, three cases diagnosed as FA on CNB were upgraded to PT on excision specimens. Nine cases diagnosed as PT on CNB were diagnosed as FA on excision specimens. These included conventional, cellular, juvenile, and complex FA types. Three PTs, which were reported as FA on CNB, measured 6, 12.5, and 17.5 cm in the greatest dimension. Among 23 cases of PT which were further categorized on CNB, tumor categories changed on excision specimens in three cases. The diagnostic accuracy of CNB diagnosis was 90.4%. Conclusion CNB diagnosis showed good accuracy. PT diagnosis should be strongly considered in all tumors measuring >5 cm, especially those exceeding 10 cm. Cellular, juvenile, and complex FAs can be misdiagnosed as PT on CNB. Correlation with clinical and radiological findings can be helpful in establishing correct diagnosis.

Fibroepithelial Neoplasm with Hybrid Features of Benign Phyllodes Tumor, Juvenile Papillomatosis, and Juvenile Fibroadenoma: A Case Report.

Phyllodes tumor is an uncommon breast fibroepithelial neoplasm mainly found in middle-aged patients, presenting a morphologic continuum from benign to malignant. Juvenile papillomatosis represents a rare benign proliferative breast tumor primarily affecting young individuals and carries a potential elevated risk of subsequent breast cancer development. Juvenile fibroadenoma is a well-circumscribed biphasic neoplasm that often occurs in adolescent girls, characterized by a pericanalicular growth pattern with usual-type epithelial hyperplasia and gynaecomastia-like micropapillary proliferation. Herein, we present an unusual example of a 26-year-old woman with a left breast outer lower quadrant palpable mass. Ultrasonography identified a 5.9 cm lobulated hypoechoic solid mass with scattered small cysts. The preoperative biopsy initially diagnosed a fibroepithelial lesion, considering giant cellular fibroadenoma and phyllodes tumor in the differential. Subsequent complete excision revealed areas of benign phyllodes tumor features closely admixed with distinctive elements such as prominent multiple cysts exhibiting apocrine and papillary apocrine metaplasia, duct papillomatosis, and duct stasis characteristic of juvenile papillomatosis, and hyperplastic ductal epithelium with micropapillary projections demonstrating a pericanalicular growth pattern indicative of juvenile fibroadenoma. The diagnosis was conclusively established as a fibroepithelial lesion with combined features of benign phyllodes tumor, juvenile papillomatosis, and juvenile fibroadenoma. Further investigation uncovered a family history of breast cancer. Molecular analysis revealed a pattern of unique and overlapping mutations within these distinct histopathological areas. This unusual presentation with hybrid features within a single tumor is described for the first time in the literature along with the molecular signature of the individual components.

De-escalating indications for excision when breast core needle biopsy returns fibroepithelial lesion-not further characterized.

PURPOSE: Surgical excision is often performed to exclude phyllodes tumor (PT) when Core Needle Biopsy (CNB) of the breast returns fibroepithelial lesion-not further characterized (FEL-NFC). If imaging or CNB pathology features can be identified that predict a very low probability of borderline/malignant PT, thousands of women could be spared the expense and morbidity of surgical excisions. METHODS: This retrospective cohort study includes 180 FEL-NFC from 164 patients who underwent surgical excisional biopsy. RESULTS: The upgrade rate from FEL-NFC to benign PT was 15%, and to borderline/malignant PT 7%. Imaging features predicting upgrade to borderline/malignant PT included greater size (p = 0.0002) and heterogeneous echo pattern on sonography (p = 0.117). Histologic features of CNB predicting upgrade to borderline/malignant PT included "pathologist favors PT" (p = 0.012), mitoses (p = 0.014), stromal overgrowth (p = 0.006), increased cellularity (p = 0.0001) and leaf-like architecture (p = 0.077). A three-component score including size > 4.5 cm (Size), heterogeneous echo pattern on sonography (Heterogeneity), and stromal overgrowth on CNB (Overgrowth) maximized the product of sensitivity x specificity for the prediction of borderline/malignant PT. When the SHO score was 0 (72% of FEL-NFC) the probability of borderline/malignant PT on excision was only 1%. CONCLUSION: The combination of size ≤ 4.5 cm, homogeneous echo pattern, and absence of stromal overgrowth is highly predictive of a benign excision potentially sparing most patients diagnosed with FEL-NFC the expense and morbidity of a surgical excision.

Clinicopathological Parameters Predicting Malignancy in Phyllodes Tumor of the Breast.

Introduction Phyllodes tumor (PT) is an uncommon fibroepithelial neoplasm of the breast. It is a biphasic tumor with stromal and epithelial components, with a tendency to recur. Because of its wide range of disease manifestations, it has been subclassified into three categories, i.e., benign, borderline, and malignant, based on several histological parameters. This study was conducted to evaluate the clinicopathological features associated with malignancy in breast PTs. Methods We conducted a retrospective study at the Department of Histopathology at Liaquat National Hospital, Karachi, Pakistan. A total of 146 biopsy-proven cases of PTs were enrolled in the study. Clinical data were obtained from the clinical referral forms. Specimens were obtained from either lumpectomy or simple mastectomy. The specimens obtained were received at the laboratory where after gross examination, paraffin-embedded tissue blocks were prepared, which were sectioned, stained, and studied by a senior histopathologist. Pathological features, such as mitotic count, necrosis, stromal atypia, stromal overgrowth, and heterologous elements, were observed. Based on these features, the PTs were classified into benign, borderline, and malignant tumors. Results The mean age of the PTs in our setup was 40.65 ± 12.17 years with a mean size of 9.40 ± 6.49 cm. Malignant PT was found to be the most prevalent in our population, accounting for 63 (43.2%) cases, followed by borderline (51, 34.9%) and benign (32, 21.9%). A significant association was found between the tumor subtype and patient age, i.e., patients diagnosed with malignant and borderline PTs were found to be of older age (mean 42.82 ± 12.94 and 42.05 ± 11.31 years, respectively) than those diagnosed with benign PTs (mean age 34.12 ± 9.75 years). Moreover, malignant PTs were associated with larger tumor size (mean 11.46 ± 6.08) compared with the other two subtypes. Conclusion We found a significant association among patient age, tumor size, and PT subtype. Therefore, apart from the usual histological parameters, patient age and tumor size are important parameters for predicting the behavior of breast PT and should be considered for management.

Fibroadenoma vulva: Experience based on FNA of vulvar lesion.

Vulval fibroadenoma is an extremely rare lesion, mostly seen in young adults. A 51-years-old woman presented with a painless, mobile, and pedunculated vulval mass. Fine-needle aspiration (FNA) was performed and was diagnosed as a benign fibroepithelial lesion possibly fibroadenoma vulva, which was later confirmed as fibroadenoma vulva histopathologically. It is just not rare to find fibroadenoma vulva, but this should also be kept as a differential when diagnosing such cytomorphology in FNA lesions. This is important to avoid unnecessary incisional biopsy before excision.

Fibroepithelial Lesion Spectrum: A Case Report Documenting a Possible Transformation to a Malignant Phyllodes Tumor.

We discuss the radiological-pathological aspects of a rare case of transformation of a presumed fibroadenoma (FA) to a malignant phyllodes tumor (PT) and review the literature. Phyllodes tumors often show heterogeneous histologic features with some areas indistinguishable on core needle biopsy. A core biopsy is often a small representation of a larger lesion. As such, a complete excisional biopsy is often needed for a definitive pathologic diagnosis. Careful clinical and imaging correlation and follow-up are necessary, even in a benign fibroepithelial lesion (FEL).

"Growing fibroadenoma": Are there clinical and pathological features predicting a phyllodes tumor on surgical excision?

In cases of growth of FA on imaging, core needle biopsies (CNB) are often performed to rule out phyllodes tumor (PT). We aim to focus on "growing FAs" and to identify clinical and histopathologic features that are likely to predict a PT on excision. Thirty-four FAs with radiologic documentation of growth were included. Various clinical and pathological features such as age, body mass index (BMI), lesion size, and growth rate were recorded. On excision, 17 cases (50 %) were FAs, whereas 16 (47 %) were re-classified as benign PT despite only 19 % being suspicious for PT on CNB. PT patients were older (mean age 42.6) than those with FAs (mean age 28.2), p = 0.0002. All false negative cases demonstrated intracanalicular growth. Mitotic rate was the most significant histologic feature in PT on excision compared to others, such as lesion circumscription and stromal cellularity. Recognition and careful counting of mitotic rate, especially with intracanalicular patterns in growing FAs, can potentially prevent missing a PT on CNB. In patients with "growing FAs" who are ≥40 years of age, excision may be recommended due to the high likelihood of PT diagnosis on excision and high false negative rate on CNB.

Race-Related Differences in the Clinical Presentation and Histopathologic Features of Phyllodes Tumor.

BACKGROUND: Phyllodes tumor (PT) is a rare fibroepithelial lesion of the breast with variable malignant potential. Black women have a higher incidence of a related benign tumor, fibroadenoma, but there are limited epidemiological data on PT. The aim of our study was to evaluate race-related differences in the clinicopathologic features and outcomes of PT. METHODS: Our institutional pathology database was queried for breast specimen reports from 01/2009 to 10/2019 to identify patients with a pathologic diagnosis of PT. Chart review and detailed slide review were performed to obtain clinical and histopathologic variables, respectively. RESULTS: Among twelve patients, two had malignant PT, three had borderline PT, and seven had benign PT. All patients with malignant and borderline PT were black, compared with 29% of those with benign PT. There were no apparent race-related differences in specific histopathologic features among black vs. non-black women with benign PT. Malignant and borderline PT were relatively larger than benign PT, with mean tumor sizes of 9.0 cm (standard deviation [SD] 4.7 cm), 12.2 cm (SD 9.4 cm), and 5.4 cm (SD 5.8 cm), respectively. Two women had a local recurrence, both of whom were black. DISCUSSION: In this single-institution retrospective study, we observed disproportionate rates of aggressive histopathologic features and disparate outcomes among black women with PT. A multi-institutional PT registry would facilitate improved knowledge about race-related differences in the presentation and outcomes of this rare tumor.

Complex Fibroadenoma with Pronounced Squamous Metaplasia: A Rare Case Report, Differential Diagnostic Considerations, and Associated Breast Cancer Risk.

Squamous metaplasia of the breast is a rare and unusual finding. A number of benign and malignant differential entities exist when squamous cells are present in a breast lesion. Our patient was found to have pronounced squamous metaplasia and keratin cysts arising in a complex fibroadenoma. The rare nature of squamous metaplasia arising in such a lesion poses some diagnostic challenges, as squamous epithelium and squamous metaplasia in the breast may raise suspicion for malignancy. Herein we present a unique case and discussion of benign and malignant differential entities. We also retrospectively reviewed a series of complex fibroadenomas in our institution, including the demographic and histologic features, and more importantly the associated breast cancer risk.

Transformation of a Benign-Appearing Fibroepithelial Lesion to a Giant Malignant Phyllodes Tumor of the Breast.

This is a case of a woman who presented with a left breast mass that was initially diagnosed as fibroadenoma on core biopsy and, after three years without any surgical intervention, was found to be a malignant phyllodes tumor. Initially, a core needle biopsy of the mass showed probable fibroadenoma. Because of the initial benign seeming diagnosis and the need to treat her tongue cancer, the patient did not recognize the need for a recommended surgical consultation and excision. Three years later, she presented after the mass had enlarged to encompass nearly the whole left breast. Core needle biopsy revealed spindle cell proliferation with scattered benign-looking tubules. Due to the large size of the mass, she underwent a total mastectomy, and the final pathology demonstrated a malignant phyllodes tumor. This case demonstrates a case of progression of a benign-appearing fibroepithelial lesion to a malignant phyllodes tumor three years later.

Radiologic-Pathologic Correlation of Fibroepithelial Lesions: A Pictorial Review.

Fibroepithelial lesions (FEL) of the breast encompass a spectrum of masses ranging from benign to malignant. Although these lesions are on the same biologic spectrum, differences in their clinical behaviors necessitate different management approaches. While imaging features are nonspecific, small size (less than 3 cm), oval shape, circumscribed margins, growth in diameter less than 20% in six months, and homogeneous echotexture on US favor fibroadenoma (FA). Conversely, larger size (3 cm or larger), rapid growth, irregular shape, noncircumscribed margins, and heterogeneous echotexture suggest possible phyllodes tumor (PT). Histopathologically, increased stromal cellularity, stromal atypia, and mitotic activity characterize PT, while FA typically lack these features. In this review, we summarize the imaging and pathology characteristics of nonmalignant FEL, including simple, juvenile, and complex FA, and benign and borderline PT and highlight the collaborative role of radiologists and pathologists in informing diagnosis and clinical management.

Tumor filodes bilateral, una rara forma de manifestación clínica: reporte de caso / Bilateral phyllodes tumor, a rare form of clinical presentation: A case report

Resumen ANTECEDENTES: La incidencia de tumores filodes es del 0.3 al 1% de todos los tumores primarios de la mama. Su presentación bilateral puede ser sincrónica o asincrónica y es excepcional. Estos tumores se clasifican (OMS) en fibroepiteliales, benignos, limítrofes o malignos. Aparecen en mujeres con límites muy amplios de edad, aunque lo más frecuente es entre los 35 y 55 años. El diagnóstico definitivo se establece con base en el reporte histopatológico. Su tratamiento es quirúrgico. CASO CLÍNICO: Paciente de 50 años, con antecedentes obstétricos de dos embarazos y dos cesáreas. Acudió a consulta debido a la aparición de una masa palpable en ambas mamas. Carecía de antecedentes relevantes para cáncer de mama. Con base en la mastografía se determinó que se trataba de un tumor categoría BI-RADS 4A. La biopsia excisional, con estudio transoperatorio, determinó que era un tumor filodes de bajo grado (benigno). Se procedió a la extirpación de ambos tumores, con márgenes libres suficientes, a fin de disminuir el riesgo de recidivas. Se determinó un plan de seguimiento con mastografía anual en las que se ha obtenido la categoría BI-RADS 2. Hasta el momento, la paciente permanece libre de enfermedad. CONCLUSIONES: Los tumores filodes son sumamente raros y más aún su aparición bilateral. Es importante integrar un diagnóstico temprano y efectuar un correcto procedimiento quirúrgico que evite las recidivas porque éstas tienden a ser cada vez más agresivas. Sigue siendo motivo de controversia la indicación de radioterapia y quimioterapia en estos tumores, que solo se reservan como tratamiento alternativo ante tumores sumamente agresivos.

Abstract BACKGROUND: The incidence of phyllodes tumors is 0.3% to 1% of all primary breast tumors. Their bilateral presentation may be synchronous or asynchronous and is exceptional. These tumors are classified (WHO) as fibroepithelial, benign, borderline or malignant. They appear in women with very wide age limits, although the most frequent is between 35 and 55 years of age. The definitive diagnosis is established based on the histopathological report. Treatment is surgical. CLINICAL CASE: 50-year-old patient with obstetric history of two pregnancies and two cesarean sections. She came for consultation due to the appearance of a palpable mass in both breasts. She had no relevant history of breast cancer. Based on the mastography it was determined to be a BI-RADS 4A category tumor. The excisional biopsy, with trans-operative study, determined that it was a low-grade (benign) phyllodes tumor. Both tumors were excised, with sufficient free margins, in order to reduce the risk of recurrence. A follow-up plan was determined with annual mastography in which BI-RADS category 2 has been obtained. So far, the patient remains free of disease. CONCLUSIONS: Phyllodes tumors are extremely rare and even more so their bilateral occurrence. It is important to integrate an early diagnosis and to perform a correct surgical procedure to avoid recurrences because they tend to be more and more aggressive. The indication of radiotherapy and chemotherapy in these tumors remains controversial and is only reserved as an alternative treatment for highly aggressive tumors.

Diagnosis on Excision Biopsy of Breast Tissues Labeled As Fibroepithelial Tumors on Trucut Samples in a Developing Country.

INTRODUCTION: Fibroadenomas (FAs) and phyllodes tumors (PTs) are less prevalent but allied to have malignant transformation in many instances. It is a challenge to diagnose the phyllodes by conventional trucut biopsy technique. OBJECTIVE: To evaluate the histological characteristics of tumors labeled as fibroepithelial lesions of breast tissues on trucut biopsy and compare with a diagnosis on excision biopsy. METHODS AND MATERIALS: It was a descriptive cross-sectional study that was carried out in Shaukat Khanum Memorial Hospital and Research Centre within six years from January 2015 to January 2021. In trucut samples, stromal cellularity, stromal cell nuclear atypia, mitotic count, stromal overgrowth, the enhancement of stromal cellularity adjacent to epithelium were scrutinized. In each category, the activity was seen as absent, mild, moderate, or severe. Mitotic activity was graded as 0-1, 0-5, 5-10, >10. RESULTS: A total of 125 patients were registered for the study. The mean age of patients in our study was 33.86 ± 9.95 years. The mean size was 41.02 ± 27.38 mm with a mean lump duration of 7.52 ± 5.34 months. In the FA group, the trucut sampling report showed the stromal cellularity as mild in 62 (69.7%) and stromal cell nuclear atypia as absent in 68 (76.4%) cases. But in the phyllodes tumor group, the stromal cellularity was severe in 10 (27.8%) patients and stromal cell nuclear atypia was severe in five (13.9%). The ultimate outcome showed that 89 (71.2%) patients had FA and 36 (28.8%) had PT at excision. CONCLUSION: Assessment of tumor size, stromal cellularity, mitoses, and enhancement of stromal cellularity adjacent to epithelium are useful markers for diagnosing the PT in trucut needle biopsy.

Keratin cyst as a diagnostic pitfall in aspiration cytology of phyllodes tumor.

BACKGROUND: Phyllodes tumor (PT) is a fibroepithelial lesion of breast known for presence of a heterogenous stroma. However occurrence of a keratin cyst within PT is a rare incidence. An inadequate sampling during fine needle aspiration (FNA) of such lesions may result in an erroneous cytological diagnosis. CASE REPORT: In the present case, ultrasound guided FNA smears from the breast lump in a 31-year-old lady with a clinical suspicion of malignancy, were repeatedly interpreted as an epidermal inclusion cyst, which was ultimately reported as a borderline PT on mastectomy. CONCLUSION: The case report aims at highlighting the importance of a diligent FNA technique keeping in mind the possibility of the various uncommon lesions especially while dealing with such a heterogenous tumor as phyllodes.

Phyllodes Tumors of the Breast: A Single-Center Experience.

OBJECTIVE: We aimed to analyze the clinicopathological findings, treatment approach, and treatmen outcomes in patients diagnosed with phyllodes tumor (PT). MATERIALS AND METHODS: The clinicopathological data of 26 patients with PT, who were treated between 2008 and 2019, were retrospectively analyzed. RESULTS: Mean age was 35.07±13.95 years (range: 14-71), while mean tumor size was 54.76±29.24 mm (range: 25-135). Benign, borderline, and malignant PT were detected in 18 (69.2%), 3 (11.5%), and 5 (19.2%) patients, respectively. Marginless excision was performed in 20 patients (76.9%), while six (23.1%) patients underwent mastectomy. A statistically significant correlation of tumor type with mean tumor size and mean age was observed (p=0.041 and p=0.013, respectively). Margin positivity on first excision was more frequent in the malignant tumors (p=0.02). No statistically significant correlation of PT type with presence of breast cancer in the family history, and tumor localization was observed (p=0.79 and p=0.13, respectively). Mean postoperative follow-up duration was 56 months (range: 6-147). Local recurrence was not observed in any of the patients. Lung and left vastus lateralis muscle metastases were encountered. The patient with lung metastasis became exitus because of the same reason 6 months after detection of the metastasis. CONCLUSION: PT is a rare fibroepithelial tumor of the breast that is characterized by a mixed histology seen in younger ages when compared to the classical breast tumors. The probability of PT should be considered in the presence of a rapid-growing mass in the breast. In addition, it should also be considered that the contribution of imaging techniques may be limited.

Recurrent myoid hamartoma of the breast mimicking malignancy.

Myoid (muscular) hamartoma is a rare form of benign breast hamartoma composed of differentiated mammary glandular and stromal structures, fatty tissue and areas of smooth muscle from which its name originates. It is considered to be a variant of a mammary hamartoma. We report the clinical presentation, imaging appearances and treatment of the initial and recurrent presentation of this rare tumour in a 61year old female, which mimicked malignancy.  Although rare, myoid hamartoma's can reoccur and when they do they imaging appearances of benign and malignant tumours can overlap tend to mimic malignancy and histological diagnosis is mandatory.

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.

A Radiomics Approach for the Classification of Fibroepithelial Lesions on Breast Ultrasonography.

A radiomics-based classifier to distinguish phyllodes tumor and fibroadenoma on gray-scale breast ultrasonography was developed and validated. A total of 93 radiomics features were extracted from representative transverse plane ultrasound images of 182 fibroepithelial lesions initially diagnosed by core needle biopsy. High-throughput radiomics features were selected using the intra-class correlation coefficient between two radiologist readers and the Least Absolute Shrinkage and Selection Operator regression through 10-fold cross-validation. When applied to the validation set, the radiomics classifier for the differentiation of phyllodes tumors and benign/fibroadenomas achieved an area under the receiver operating characteristic curve of 0.765 (95% confidence interval [CI]: 0.597-0.888) with an accuracy of 0.703 (sensitivity: 0.857; specificity: 0.5). Our radiomics signature-based classifier may help predict phyllodes tumors among fibroepithelial lesions on breast ultrasonography.

Imaging and management of fibroepithelial breast lesions on percutaneous core needle biopsy.

The purpose of this study is to review the clinical presentation, multi-modality appearance, and management of the most common benign and malignant fibroepithelial lesions of the breast. Fibroepithelial lesions of the breast may exhibit characteristic features on mammography, ultrasound, and MRI, although definitive diagnosis most often requires biopsy and at times, surgical excision. Knowledge of the imaging features can assist in refining the differential diagnosis and guiding appropriate management.

Phyllodes Tumor of the Breast: A Clinicopathological Evaluation of 55 Cases.

OBJECTIVE: Phyllodes tumors are biphasic tumors consisting of epithelial and stromal components that account for less than 1% of all breast tumors. According to the World Health Organization (WHO) phyllodes tumors are classified into three categories as benign, borderline and malignant. It has been reported that these tumors are usually benign and both the stromal component and the epithelial component may progress to malignancy. In this descriptive study, it was aimed to present the cases of phyllodes tumor and to evaluate the clinicopathological features of these tumors in the light of the literature. MATERIALS AND METHODS: In our study, 55 cases of phyllodes tumor diagnosed between 2005-2018 in the Department of Medical Pathology were retrospectively studied. A total of 55 cases were included in the study. RESULTS: All cases were female with a mean age of 39.7+15.2 years. Fifty-seven tumors diagnosed in 55 cases were classed as benign in 20 cases (35.1%), borderline in 14 cases (24.6%) and malignant phyllodes tumors in 23 cases (40.3%). Ductal carcinoma in situ (solid and cribriform type) were detected in one case with malignant phyllodes tumor, whereas invasive ductal carcinoma was detected in one case. Bilateral ductal carcinoma in situ was present in the patient with invasive ductal carcinoma. CONCLUSION: These tumors which rapidly grow into large masses can be clinically and pathologically confused with benign lesions, macroscopic and microscopic evaluation of concomitant in situ-invasive carcinomas should be considered. Phyllodes tumors have an important role in breast surgery and pathology.