Benign spindle cell tumors of the mammary stroma: diagnostic criteria, classification, and histogenesis

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.

Myofibroblastoma of the Breast: Diagnosis, Pathology, and Management

Myofibroblastomas are rare benign spindle cell tumors that occur within both male and female breasts. They are composed of fibroblasts and myofibroblasts and are not associated with malignant potential. On mammographic and sonographic imaging, these tumors may present as oval circumscribed masses that overlap with the appearance of many benign entities, including fibroadenomas. Occasionally, the tumors may demonstrate interval growth or mimic imaging features of malignancy and require biopsy. Correct pathologic diagnosis is important because many morphologic variants exist, which complicates pathologic interpretation. The purpose of this article is to review the range of imaging manifestations and histopathological findings and to discuss current management.

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.

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

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

Practical approach to diagnosis of bland-looking spindle cell lesions of the breast

The diagnosis of bland-looking spindle cell lesions of the breast is often challenging because there is a close morphological and immunohistochemical overlap among the different entities. The present review will discuss reactive spindle cell nodule/exuberant scar, nodular fasciitis, inflammatory pseudotumor, myofibroblastoma (classic type), lipomatous myofibroblastoma, palisaded myofibroblastoma, benign fibroblastic spindle cell tumor, spindle cell lipoma, fibroma, leiomyoma, solitary fibrous tumor, myxoma, schwannoma/neurofibroma, desmoid-type fibromatosis, dermatofibrosarcoma protuberans, low-grade fibromatosis-like spindle cell carcinoma, inflammatory myofibroblastic tumor and low-grade myofibroblastic sarcoma arising in the breast parenchyma. The pathologist should be aware of each single lesion to achieve a correct diagnosis to ensure patient a correct prognostic information and therapy. Accordingly representative illustrations and morphological/immunohistochemical diagnostic clues will be provided.

A case report of a mammary myofibroblastoma in a male and literature review of radiologic and pathologic features of breast myofibroblastoma

We reported a 65-year-old male with a benign mammary myofibroblastoma. This report shows that not all masses of male breast are malignant. To differentiate benign masses from malignant neoplasms, careful preoperative diagnosis should be performed. Preoperative diagnosis of the tumor prevents placing a huge financial and mental burdens on patients.

Utility of STAT6 and 13q14 deletion in the classification of the benign spindle cell stromal tumors of the breast

The boundaries of the benign spindle cell stromal tumors of the breast are still confusing. This is the reason why different names are interchangeably used for the same tumor and vice versa the same name for different tumors. Therefore, we studied the immunoexpression of easily available markers, such as CD34, α-smooth muscle actin, and desmin, with the addition of STAT6, as well as the chromosome 13q14 region by fluorescence in situ hybridization analysis in a series of 19 cases of benign spindle cell stromal tumors of the breast. Based on the morphologic and immunohistochemical findings, the following histotypes were identified: (i) tumors (10/19 cases) with the characteristic morphology of myofibroblastoma and stained with vimentin, CD34, desmin, and α-smooth muscle actin; (ii) fibroblastic benign spindle cell tumors (5/19 cases) composed of fibroblast-like cells stained only with vimentin and CD34; (iii) tumors (2/19 cases) with the typical morphologic features of solitary fibrous tumor and stained with vimentin, CD34, and STAT6; (iv) 1 case of spindle cell lipoma stained with vimentin and CD34; and (v) 1 case of fibroma composed of a paucicellular, diffusely hyalinized stroma with expression of vimentin and CD34. Notably most of the tumors, with the exception of solitary fibrous tumor, showed monoallelic deletion of FOXO1. This finding supports that myofibroblastoma, fibroblastic benign spindle cell tumor, spindle cell lipoma, and fibroma of the breast are histogenetically related lesions which belong to the same tumor entity.

Benign Fibromyxoid Lesion of the Breast: A Distinct Entity From Benign Spindle Cell Tumors of the Mammary Stroma?

Myxoid lesions of the breast can be diagnostically challenging entities. We report 4 cases of CD34+ fibromyxoid lesion that have been previously diagnosed as “benign myxoid lesion,” “nodular mucinosis,” or “mammary myofibroblastoma, myxoid type” on the basis of CD34-positivity. The lesions were microscopically well circumscribed and composed of a paucicellular spindle cell proliferation in a background of myxoid stroma. No epithelial component was identified. The spindle cells showed immunohistochemical reactivity for CD34 and smooth muscle actin. Based on morphologic and immunohistochemical similarities between these cases and myxoid myofibroblastoma, we compared 4 myxoid lesions with cases of typical myofibroblastoma, utilizing retinoblastoma (Rb) antibody and fluorescent in situ hybridization for 13q14 gene rearrangement (encoding the Rb gene). The myxoid lesions showed retention of Rb protein by immunohistochemistry, whereas Rb expression was lost in cases of myofibroblastoma. We identified loss of 13q14 in 3 of 4 cases of myofibroblastoma. Notably, 13q14 gene rearrangement was not observed in any of the myxoid lesions. Our data show that there is at least a subset of CD34+ fibromyxoid lesions that, despite overlapping morphologic and immunohistochemical phenotype and proposed common histogenesis with myofibroblastomas, is genetically distinct from the latter based on Rb analysis.

Leiomyoma of the breast parenchyma: a case report and review of the literature

INTRODUCTION

Benign tumors are often seen in breast screening examinations. However, the differential diagnosis is not always simple because of radiological similarity between the different benign lesions.

CASE REPORT

We present a rare case report of leiomyoma of the breast parenchyma in a 68-year-old asymptomatic patient. The mammographic and ultrasonographic findings were similar to those observed in benign lesions.

CONCLUSION

The histopathological diagnosis requires careful differentiation from lesions that have smooth muscle proliferation, especially leiomyosarcoma. The most commonly performed treatment is resection of the lesion with free margins. Although breast leiomyoma is rare, it should be considered among the differential diagnoses for breast nodules of benign appearance. Resection with safety margins proved to be the only treatment needed.

Differential Diagnosis of Benign Spindle Cell Lesions

Spindle cell lesions of the breast cover a wide spectrum of diseases ranging from reactive tumor-like lesions to high-grade malignant tumors. The recognition of the benign spindle cell tumor-like lesions (nodular fasciitis; reactive spindle cell nodule after biopsy, inflammatory pseudotumor/inflammatory myofibroblastic tumor; fascicular variant of pseudoangiomatous stromal hyperplasia) and tumors (myofibroblastoma, benign fibroblastic spindle cell tumor, leiomyoma, schwannoma, spindle cell lipoma, solitary fibrous tumor, myxoma) is crucial to avoid confusion with morphologically similar but more aggressive bland-appearing spindle cell tumors, such as desmoid-type fibromatosis, low-grade (fibromatosis-like) spindle cell carcinoma, low-grade fibrosarcoma/myofibroblastic sarcoma and dermatofibrosarcoma protuberans.

Mammary Myofibroblastoma in a Transgender Patient on Feminizing Hormones: Literature Review and Case Report

Purpose: Defining the risk of neoplasia associated with gender-affirming hormone therapy (GAHT) is a priority for transgender medical research. The purposes of this article are to present a unique case of breast neoplasia in a transgender individual and to review the existing evidence base on GAHT as a potential risk for breast pathology. Methods: We present the case of a 76-year-old transgender patient who developed an estrogen receptor-positive mammary myofibroblastoma (MFB) after 13 months of treatment on feminizing hormones. To our knowledge, this is the first reported case of MFB occurring in a transgender individual. A literature review was conducted to identify all reported cases of breast neoplasia among transgender individuals receiving feminizing GAHT. Information was abstracted from each of the included cases to describe the existing body of literature and to compare published cases to the case reported in this study. Results: We identified a total of 19 malignant and 3 benign cases of breast neoplasia among transgender women. Ours is the first reported case of MFB in a transgender individual receiving feminizing hormones and the first reported case of breast neoplasia associated with GAHT administered via the estradiol patch. Conclusion: This case reinforces the need for additional reporting of breast neoplasia presenting in transgender individuals treated with feminizing hormones. The relationship between estrogen exposure and breast neoplasia in the transgender population remains poorly defined, and additional research is needed to define risks and inform clinical practice.

Chondrolipoma of the breast as a rare variant of myofibroblastoma: an immunohistochemical study of two cases

Chondrolipoma of the breast is a very rare tumor whose histogenesis remains obscure. We report two cases (56-year-old and 43-year-old women) and present the results of an immunohistochemical study which strongly suggests that this tumor is a variant of myofibroblastoma. The tumors predominantly consisted of lipoma-like, mature adipose tissue, and many islands of hyaline cartilage. A proliferation of spindle cells associated with the deposition of collagen fibers was also seen. On immunohistochemical examination, spindle cells showed cytoplasmic reactivity for vimentin, desmin, bcl-2, and α-smooth muscle actin, as well as nuclear reactivity for estrogen receptor (ER) and progesterone receptor (PgR). Chondrocytes were immunoreactive for ER, PgR, S-100 protein, and Sox9. The nuclei of adipocytes, chondrocytes, and spindle cells were not immunoreactive for Rb (retinoblastoma) protein. The immunoreactivity of spindle cells for muscle markers indicates myofibroblastic differentiation, and the lack of the nuclear expression of Rb protein suggests the close relationship of this tumor with myofibroblastoma and spindle cell lipoma. The immunoreactivity of chondrocytes for ER and PgR suggests that they are derived from metaplasia of hormone-sensitive spindle cells. These findings support the concept that chondrolipoma of the breast could be a lipomatous variant of myofibroblastoma associated with cartilaginous metaplasia and that it should be added to members of the "13q/Rb family of tumors."

Lipomatous tumors of the breast: A contemporary review

Breast tumors with lipomatous or liposarcomatous components are infrequently encountered, but can be a source of diagnostic difficulty if the context of the fatty differentiation is not recognized. Among the true adipocytic tumors, lipoma is the most common lipomatous tumor arising in the breast. Several mammary spindle cell tumors may show adipocytic differentiation, including fibroepithelial tumors and myofibroblastoma. Liposarcomatous components most often arise in malignant phyllodes tumors, as opposed to primary liposarcomas of the breast which are believed to be uncommon. This article will review the spectrum fat-containing tumors of the breast with an emphasis on differential diagnosis and insights from recent molecular studies.

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.

Cytological Features of Palisaded Mammary-Type Myofibroblastoma

Palisaded mammary-type myofibroblastoma is a rare variant of benign stromal spindle cell tumor whose histological features are well known. Nevertheless, no cytological features have been reported to date. In this article, we describe the cytological features of a case of palisaded mammary-type myofibroblastoma in which a preoperative fine needle aspirate was obtained. Smears were moderately cellular, characterized by clusters of spindle cells, disposed in a parallel fashion and immersed in myxoid background. Although the lesion is rare, it is worth distinguishing from benign and malignant spindle cell tumors.

Myofibroblastoma of the Breast: Literature Review and Case Report

Myofibroblastoma of the breast is a rare benign spindle cell tumor. The main aim of this study is to review the literature of this rare tumor. We present a case of a mammary myofibroblastoma occurring in an 82-year-old man, emphasizing the clinical, radiological, and pathological features. The tumor was successfully identified and managed in our hospital. We would like to draw the attention of clinicians to myofibroblastoma as a rare possibility in the differential diagnosis of a breast mass.

Low-grade myofibroblastic sarcoma arising in fibroadenoma of the breast-A case report

BACKGROUND

Myofibroblastic sarcoma or myofibrosarcoma is a malignant tumor of myofibroblasts and known to develop rarely in the breast, but its underlying lesion and tumor cell origin have never been reported yet.

CASE PRESENTATION

A 61-year-old female presented with a gradually growing breast mass with well-demarcated ovoid nodular shape. The tumor was histologically characterized by fascicular-growing spindle cell proliferation with large areas of hyalinized fibrosis and focally ductal epithelial remnants embedded in myxoid stroma, mimicking a fibroadenomatous lesion. It had frequent mitoses of 5-16/10 high-power fields, hemorrhagic necrosis, and focally pericapsular invasion. The spindle cells were diffusely immunoreactive for fibronectin, smooth muscle actin, and calponin, which suggest a myofibroblastic origin. Multiple irregularly thickened vessels with medial or pericytic cell proliferation were found to be merged with the intrinsic tumor cells. The tumor could be diagnosed low-grade myofibroblastic sarcoma arising in an old fibroadenoma.

CONCLUSION

We report a case of a low-grade mammary myofibrosarcoma that showed a background lesion of fibroadenoma first in the worldwide literature and suggest the pericytes or medial muscle cells of the intratumoral vessels as the cell origin of the myofibroblastic sarcoma.

Myofibroblastoma of the mandible in a 3-year-old child

Myofibroblastoma is a rare benign tumor of the head and neck region, which is characterized by a large, rapidly growing, and destructive mass. A 3-year-old boy presented with an 8-week history of a rapidly growing swelling of the right mandible. Examination revealed a firm 13-cm mass occupying the entire right body and ramus of the mandible. The clinical and radiological features were suggestive of a sarcoma. An initial biopsy taken in the referring hospital was inconclusive, and the second biopsy showed a myofibroblastic neoplasm consistent with a desmoplastic fibroma. Progressive tumor growth necessitated a tracheostomy. Right hemimandibulectomy was performed, and the defect was reconstructed with free microvascular fibula flap. Histopathology and immunocytochemistry revealed a myofibroblastoma. This entity differs from other myofibroblasts and fibroblast tumors such as inflammatory myofibroblastic tumor (IMT), myofibroma, and desmoplastic fibroma. The child has been followed up for 2 years.

CONCLUSION

Differentiation between myofibroblasts and fibroblastic tumors as well as some malignancies can be challenging. Myofibroblastoma can behave as a malignant neoplasm, and the clinical distinction of this entity lies primarily in its recognition as a benign neoplasm.

Live fibroblast harvest reveals surface marker shift in vitro

Current methods for the isolation of fibroblasts require extended ex vivo manipulation in cell culture. As a consequence, prior studies investigating fibroblast biology may fail to adequately represent cellular phenotypes in vivo. To overcome this problem, we describe a detailed protocol for the isolation of fibroblasts from the dorsal dermis of adult mice that bypasses the need for cell culture, thereby preserving the physiological, transcriptional, and proteomic profiles of each cell. Using the described protocol we characterized the transcriptional programs and the surface expression of 176 CD markers in cultured versus uncultured fibroblasts. The differential expression patterns we observed highlight the importance of a live harvest for investigations of fibroblast biology.

Wilms' tumor protein (WT1) in mammary myofibroblastoma: an immunohistochemical study

Wilms' tumor protein (WT1) has been immunohistochemically detected in the cytoplasm of some developing, adult normal and neoplastic human tissues, suggesting its complex regulator activity in transcriptional/translational processes. Among neoplastic tissues, WT1 has been documented in the cytoplasm of benign and malignant vascular tumors and in rhabdomyosarcoma, while there are no available studies about its expression in myofibroblastic tumors. Accordingly, we studied immunohistochemically the potential expression of WT1 in mammary myofibroblastoma (MFB), a prototypical myofibroblastic tumor. A series of 18 cases of mammary MFB, including several morphological variants (classic, fibrotic, myxoid, lipomatous, Schwannian-like, and epithelioid variants), were tested with antibodies against the N-terminal of WT1. The most striking finding was a diffuse and strong WT1 cytoplasmic immunostaining restricted to the "epithelioid cell MFB", a rare and diagnostically challenging variant. Conversely the other variants of MFB, including the classic-type, were negative or only focally positive. The present study shows that mammary epithelioid cell MFB should be added to the list of mesenchymal tumors which express WT1 in the cytoplasm of neoplastic cells. Accordingly, we suggest that the detection of WT1 cytoplasmic immunoreactivity is of complementary diagnostic value to conventional myofibroblastic markers in identifying epithelioid cell myofibroblastoma.

[Differential diagnosis of spindle cell tumors of the breast from biopsy material]

Spindle cell proliferations are a rare but diagnostically challenging finding in breast biopsy material. The spectrum of possible diagnoses ranges from benign lesions, such as hamartomas, myofibroblastomas and biphasic tumors, such as adenomyoepitheliomas to malignant lesions, such as metaplastic carcinomas, phyllodes tumors and genuine sarcomas. A correct diagnosis from the preoperative biopsy material helps prevent inappropriate therapy and overtreatment or undertreatment. In this review five morphological patterns of spindle cell tumors of the breast and the most important representatives in this group are discussed.

Atypical epithelioid cell myofibroblastoma of the breast with multinodular growth pattern: a potential pitfall of malignancy

Myofibroblastoma (MFB) of the breast is the prototypical benign spindle cell tumor arising from the mammary stroma. Over the last two decades, several morphological variants of this tumor have been recognized. Epithelioid cell MFB is composed predominantly of neoplastic elements with epithelioid morphology. It represents a potential diagnostic pitfall of malignancy, especially when evaluating small biopsies. We report a unique case of a mammary epithelioid cell MFB composed of large mono- to multi-nucleated cells showing mild to moderate nuclear pleomorphism, predominantly arranged in a multinodular growth pattern. This tumor needs to be distinguished from invasive apocrine, oncocytic, pleomorphic lobular carcinoma, as well as metastases. Immunohistochemistry revealed the fibroblastic/myofibroblatic (positivity for vimentin, desmin, CD34 and focally for α-smooth muscle actin) nature of proliferating cells, and therefore was crucial for a correct diagnosis.

Undifferentiated pleomorphic sarcoma with osteoclast-like giant cells of the female breast

The authors describe a case of undifferentiated pleomorphic sarcoma of the breast occurring in a 50-year-old woman who presented with a palpable mass in her right breast. She first noticed the mass one month previously. Core needle biopsy showed connective tissue including epithelioid and spindle cells. The patient underwent total mastectomy without axillary lymph node dissection. Based on examination of the excised tumor, the initial pathologic diagnosis was atypical spindle-shaped and ovoid cells with uncertain malignant potential. Histological findings with immunomarkers led to the final diagnosis of undifferentiated pleomorphic sarcoma.

This case highlights a rare and interesting variant of primary breast sarcoma and the important role of immunohistochemistry in defining histological type and differential diagnosis. Hence, undifferentiated pleomorphic sarcoma has been a diagnosis of exclusion performed through sampling and critical use of ancillary diagnostic techniques.

Undifferentiated pleomorphic sarcoma of the male breast causing diagnostic challenges

Undifferentiated pleomorphic sarcoma of the breast are uncommon and often present diagnostic challenges. Herein, we report a case of the undifferentiated pleomorphic sarcoma occurring in the male breast. A 76-year-old man presented with a palpable bean-sized mass in his left breast for two months. Core needle biopsy revealed the presence of atypical cells in a fibrous proliferative lesion, which was removed by wide excision. Based on examination of the excised tumor, the initial pathologic diagnosis was atypical spindle cell lesion with uncertain malignant potential. One year later, the patient returned with a recurrent mass atthe previous surgical site. The mass was again surgically removed using wide excision. Based on histological findings with immunomarkers, the final diagnosis was undifferentiated pleomorphic sarcoma. Undifferentiated pleomorphic sarcoma of the breast can cause genuine diagnostic difficulty and appropriate immunohistochemistry is mandatory for differential diagnosis.

Mammary myofibrosarcoma: case report and literature review

A case of myofibrosarcoma of breast is reported. A female patient aged 81 years presented with a mammary mass lesion. Histologically, the tumor consisted of neoplastic spindle cells arranged in fascicles and with variably cellularity and hyalinization. Immunohistochemical studies showed expression of vimentin, smooth-muscle actin, and Bcl-2, but not desmin, S-100, C-kit, or CD34. Proliferative index identified by Ki67 was approximately 30%. Electron microscopy revealed variable amount of rough endoplasmic reticulum, myofilaments, fibronexus junctions, and fibronectin fibrils. The histological, immunohistochemical, and ultrastructural features of this tumor were consistent with myofibrosarcoma. This case will be one of the very few cases of ultrastructurally confirmed mammary myofibrosarcoma reported in the literature and contributes to the recognition of this rare mammary malignant neoplasm. The literature on mammary myofibrosarcoma and its differential diagnosis is also reviewed.

Myofibroblastoma of the breast: Case report and literature review

Myofibroblastoma of the breast is a rare benign mesenchymal tumor. The literature describes relatively few cases of this type of tumor. We report on a new case of myofibroblastoma in a 65-year old man successfully managed at our institution. The purpose of this case report is to highlight characteristics and differential diagnosis of this rare neoplasm.

Myofibroblastoma arising in mammary hamartoma: a case report

Myofibroblastoma (MFB) is a rare mesenchymal tumor arising in breast's soft tissue with a great variety of microscopic features that can be mistaken with a wide variety of biphasic lesions. The authors report a rare case of myofibroblastoma of the breast arising in a mammary hamartoma (MH), present a review of the clinicopathological features of these lesions, and make some diagnostic considerations. The tumour consisted of a well-circumscribed nodule. MFB component comprised about fifty percent of the lesion and was made up of bipolar spindle cells arranged in fascicular clusters separated by bands of hyalinized collagen. There were fat cells and several residual hamartoma glands intermingled and distorted in MFB area. MFB component was positive for Desmin, CD34, bcl-2, and Calponin. To the best of our knowledge, MFB has not been reported in MH, neither has any of the reports described mammary glands joined within MFB.

Benign spindle cell tumor not otherwise specified (NOS) in a male breast

Breast spindle cell tumors (BSCTs), although uncommon, constitute a heterogeneous group of benign and malignant lesions, often necessitating different therapeutic approaches. This study describes the case of a 62-year-old man who displayed a gradually growing retroareolar tumor of the left breast. The mass was well circumscribed, unilateral, and grossly nodular. The patient eventually underwent wide local excision of the mass. The lesion was made up of spindle cells arranged in fascicular clusters, separated by bands of collagen. No mitotic figures were observed. Immunohistochemically, the mass expressed strong and diffuse cytoplasmic staining for vimentin, CD34, CD10, and bcl-2, whereas it was negative for cytokeratins, smooth muscle actin, desmin, S-100 protein, p53, Ki-67, estrogen and progesterone receptors. Diverse histological results and immunohistochemical features established the diagnosis of benign BSCT, not otherwise specified. The patient remains disease-free 12 months after lumpectomy. This case report adds to the spectrum of the benign BSCTs and delineates the nature of different types of these lesions, in order to carefully select optimal therapeutic regimes.

Mammary Myofibroblastoma: A Tumor With a Wide Morphologic Spectrum

Context.—Myofibroblastoma (MFB) of the breast is an unusual benign tumor that belongs to the family of the “benign spindle cell tumors of the mammary stroma.” The name MFB reflects its cellular composition, comprising mainly stromal cells with fibromyofibroblastic and, less frequently, myoid differentiation. Since the original description, the morphologic spectrum of MFB has been expanded by the recognition of several unusual morphologic variants, such as the cellular, infiltrative, epithelioid, deciduoid-like, lipomatous, collagenized/fibrous, and myxoid variants.

Objective.—To review the literature on mammary MFB, discussing the main clinical, radiologic, and pathologic features helpful for diagnosis. Since MFB may show alarming morphologic features, which can lead to a misdiagnosis of malignancy, histologic figures of this tumor, including its more unusual variants, are provided to offer pathologists a practical approach to a correct diagnosis. Histogenesis and pathogenesis of this tumor are also proposed.

Data Sources.—Clinicopathologic data on MFB were extracted from all identified articles through PUB Medline– based research. Histologic figures have been taken from the personal archive of the author.

Conclusions.—The incidence of MFB diagnosis has increased in recent years, likely due to the mammographic screening. Accordingly, this unusual benign tumor may represent a potential diagnostic pitfall, especially when interpreting fine-needle aspiration and/or needle core biopsy. Pathologists should be aware of the wide morphologic spectrum exhibited by MFB to avoid a misdiagnosis of malignancy.

Solitary fibrous tumor of the breast and mammary myofibroblastoma: the same lesion?

Benign stromal tumors of the breast are rare mesenchymal neoplasms that have significant clinical and morphologic overlap. We report the case of a spindle cell tumor occurring in the mammary gland with mixed features of solitary fibrous tumor and mammary myofibroblastoma. The significance of this finding as well as the pathologic and radiologic diagnostic strategies used to differentiate these two lesions are presented based on a review of pertinent literature.