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

Mammary Myofibroblastoma: Report of a Case and Review of the Literature

Mammary myofibroblastoma is a benign mesenchymal tumor composed of fibroblasts, myofibroblasts, and a variable number of adipocytes. Mammary myofibroblastoma usually occurs in men of older age and is less common in postmenopausal women. It may also happen in extramammary sites along the milk line. In this instance, it is referred to as mammary-type myofibroblastoma. Rarely multifocal and bilateral tumors have been described. Clinically and radiologically, it can be misinterpreted as a malignant tumor due to its rarity. Size usually does not exceed 3 cm. The diagnosis requires clinicopathological correlation with morphological and immunohistochemical evaluation, especially in limited biopsy specimens. We herewith describe a rare case of mammary myofibroblastoma in a 37-year-old female patient. We also review the literature focusing on the potential differential diagnostic issues and discuss this tumor's ultrastructural and cytogenetic findings.

Retroperitoneal myofibroblastoma in an 88‐year‐old male

Introduction

Extramammary myofibroblastomas are extremely rare.

Case presentation

The patient was an 88‐year‐old male. He presented for evaluation of frequent urination and a “pushing up” sensation from the groin during defecation. Thorough physical and radiographic examinations revealed a retroperitoneal tumor on the right side of the rectum. The pathologic examination of the biopsy tissue showed that the tumor was unlikely to be malignant. Nevertheless, the patient was symptomatic and thus underwent a laparoscopic tumor resection through a transperitoneal approach. The tumor was circumscribed with a solid capsule. Based on the pathologic findings, which included immunostaining, the tumor was diagnosed as a myofibroblastoma. There was no evidence of a recurrence 6 months postoperatively.

Conclusion

We present this case with the clinical course and surgical findings, and discuss the possibility of establishing a preoperative pathologic diagnosis of a myofibroblastoma.

Epithelioid myofibroblastoma of the breast: A case report and review of the literature

INTRODUCTION

Mammary myofibroblastoma (MFB) is a rare tumour. Its clinical and pathologic characteristics have been only sporadically described. A case of epithelioid variant of MFB is reported with the diagnostic tips, the differential diagnoses, and a discussion on the possible pathogenesis.

PRESENTATION OF CASE

A 74 year-old woman presented with a painless nodule in the left breast. Core needle biopsy (CNB) revealed a tumour primarily composed of epithelioid cells. Despite epithelioid appearance of the tumour cells, ductal/lobular components were absent within the tumour. As cell lineage of the epithelioid cells could not be determined with CNB, lumpectomy was performed to obtain definitive diagnosis and, at the same time, to remove the lesion. Histologically, the tumour consisted of multiple epithelioid cell nests that were spread over fibrous stroma infiltrated with adipose tissue. Spindle cells were also present, but they were fewer than epithelioid cell clusters. Occasionally, the tumour cells showed nuclear atypia. It was difficult to determine whether this tumour was benign or malignant solely with Hematoxylin-eosin stain. However, with the aid of immunohistochemical analyses, we could make a histodiagnosis of epithelioid subtype of myofibroblastoma.

DISCUSSION

The differential diagnoses of epithelioid MFB include ductal, lobular, metaplastic carcinomas and mesenchymal tumours. Comprehensive knowledge of classic and variant MFB is necessary for the correct diagnosis.

CONCLUSION

Pathologic diagnosis of epithelioid variant of MFB requires careful evaluation of histology and the use of a panel of immunohistochemistry. Female phenotype of breast stroma may play a role in the pathogenesis of MFB.

Diagnostic challenges of intra-operative frozen consultation for mammary epithelioid myofibroblastoma

Myofibroblastoma (MFB) of the breast is a rare benign neoplasm that exhibits several morphologic variants and presents diagnostic challenges for pathologists, especially in recognizing intra-operative frozen sections. In order to raise awareness of this tumor and avoid misdiagnosis, we describe a case of a 38-year-old female patient diagnosed as epithelioid MFB. This painless tumor was well-circumscribed, found in the left breast and was physically examined over a period of six months. Histologically, this tumor was predominantly composed of epithelioid cells, which arranged as single cells, small clusters or nests. Tumor stroma was collagenized with spindle cells, adipose and focal myxoid areas. This case was misinterpreted as invasive carcinoma in the frozen section. The immunohistochemical profile demonstrated positivity for Vimentin, desmin, SMA, calponin, CD34, ER, PR and AR, whereas pan-keratin, keratin 7, keratin 34βE12, keratin 5/6, EMA, p63 and S100 were negative. RB1 was abnormally negative, confirming the diagnosis of epithelioid MFB. Making a correct diagnosis is primarily dependent on awareness by the pathologist of this unusual variant of MFB and careful integration of clinicopathologic findings to avoid potential diagnostic pitfalls.

A Rare Case of Epithelioid Myofibroblastoma of Breast Mimicking Lobular Carcinoma on Trucut Biopsy: a Diagnostic Pitfall and Literature Review

Epithelioid myofibroblastoma of the breast is a rare benign stromal tumor occurring in the postmenopausal females and elderly males. We report one such case in a 65-year-old female who underwent trucut biopsy from a well-defined right breast lump, which was misinterpreted as invasive lobular carcinoma on histology. Tumor showed mild to moderately pleomorphic tumor cells arranged in single file pattern, loosely dispersed and focally in sheets with inconspicuous nucleoli embedded in a fibrotic and hyalinized stroma. Immunohistochemistry for E-cadherin was negative further substantiating the morphological diagnosis. However, mastectomy specimen revealed it to be a case of epithelioid myofibroblastoma with the help of a large panel of immunohistochemical stains. In this report, we emphasize on the challenges of establishing this rare diagnosis mimicking lobular carcinoma, a diagnostic pitfall on trucut biopsy.

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.

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.

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.

Epithelioid mammary myofibroblastoma mimicking invasive lobular carcinoma

A case of a 53-year-old woman with the epithelioid variant of mammary myofibroblastoma, which was initially misinterpreted as invasive lobular carcinoma, is presented. A needle core biopsy of the 1.6 cm mass showed interlacing bundles of epithelioid myofibroblasts amid dense fibrous tissue associated with lobular carcinoma in situ of the classical type. Most epithelioid cells showed nuclear atypia, and a few exhibited signet-ring cytology. Immunoreactivity for estrogen and progesterone receptors further compounded the deception, and the neoplasm was misinterpreted as invasive lobular carcinoma. Excisional biopsy showed a circumscribed stromal tumor with foci suspicious for invasive lobular carcinoma. The latter was excluded by cytokeratin negativity throughout the tumor. The overall histopathological appearance and immunostaining pattern was confirmatory of myofibroblastoma. This case report emphasizes the potential for mistaking epithelioid myofibroblastoma for invasive lobular carcinoma--particularly in the setting of limited sampling, hormone-receptor immunoreactivity of the lesional cells, and synchronous lobular carcinoma in situ.

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.