Metastatic myoepithelioma of the breast

Breast lesions with myoepithelial phenotype

Myoepithelial cells (MECs) constitute a continuous layer of cells surrounding the breast glands, localised between the epithelial cells (ECs) and the basal membrane. MECs play important roles in normal mammary gland as they produce basal membrane and stimulate secretion. During neoplastic transformation, MECs act as a barrier preventing stromal invasion. MECs themselves can undergo a great variety of changes, ranging from hyperplastic to metaplastic, to neoplastic, and giving rise to a wide spectrum of morphological pictures sometimes difficult to interpret on routine diagnoses. Several benign and malignant breast tumours can present features of MECs differentiation. As these latter tumours are quite infrequent, the purpose of the present study is to offer a review of the morphological spectrum of MECs lesions, with correlations to prognosis.

Malignant Myoepithelioma of the Breast Clinically and Histologically Masquerading as Angiosarcoma: Cytological Findings and Review of the Literature

BACKGROUND

Malignant myoepithelioma of the breast is an exceptionally rare, aggressive tumor with a diverse morphology, the cytological features of which have only occasionally been described.

CASE REPORT

Our case comprises a 74-year-old woman who was admitted to our hospital with an erythematous, inflammatory-like mass of her left breast with nipple ulceration, and clinically fixed to the chest wall. The woman underwent fine-needle aspiration and biopsy. The aspirates consisted mainly of loose aggregates of large, highly pleomorphic, polygonal epithelioid cells as well as aggregates of spindle cells with prominent, easily detectable mitoses and single, multinucleated pleomorphic giant cells. The cytological diagnosis was consistent with high-grade malignancy. Histologically, the lesion consisted broadly of eosinophilic epithelioid cells with globoid cytoplasm in a reticulated, angiomatoid pattern and of spindle (sarcomatoid) cells in a storiform pattern, highly suspicious of angiosarcoma. A final diagnosis of malignant myoepithelioma was made.

CONCLUSION

We present the cytological findings in comparison with the unusual histological features of a malignant myoepithelioma of the breast. A high degree of suspicion with a keen eye for morphological details coupled with relevant immunohistochemistry will aid in arriving at the correct diagnosis.

K5/K14-positive cells contribute to salivary gland-like breast tumors with myoepithelial differentiation

Salivary gland-like tumors of the breast show a great variety of architectural patterns and cellular differentiations such as glandular, myoepithelial, squamous, and even mesenchymal phenotypes. However, currently little is known about the evolution and cellular differentiation of these tumors. For that reason, we performed an in situ triple immunofluorescence lineage/differentiation tracing (isTILT) and qRT-PCR study of basal (K5/K14), glandular (K7/K8/18), and epidermal-specific squamous (K10) keratins, p63, and smooth muscle actin (SMA; myoepithelial marker) with the aim to construct and trace different cell lineages and define their cellular hierarchy in tumors with myoepithelial differentiation. isTILT analysis of a series of 28 breast, salivary, and lacrimal gland tumors, including pleomorphic adenomas (n=8), epithelial-myoepithelial tumors (n=9), and adenoid cystic carcinomas (n=11) revealed that all tumor types contained K5/K14-positive progenitor cells in varying frequencies from a few percent up to 15%. These K5/K14-positive tumor cells were found to differentiate to glandular- (K8/18-positive) and myoepithelial-lineage (SMA-positive)-specific cells and were also shown to generate various heterologeous cell differentiations such as squamous and mesenchymal progenies. p63 was co-expressed with K5/K14 in basal-like progenitor cells, myoepithelial, and squamous cells but not in glandular cells. Our results show that the corresponding counterpart tumors of breast and salivary/lacrimal glands have identical cellular compositions. Taken together, our isTILT and RNA-expression data indicate that look-alike tumors of the breast represent a special subgroup of basal-type tumors with benign or usually low malignant potential.

Metastatic tumors in the breast: a report of 5 cases and review of the literature

Breast cancer is the most common malignancy in women. However, metastases to the breast from nonmammary malignant neoplasms are rare and were detected at a rate of 0.28% in our series. Clinical and pathologic findings in 5 cases of metastatic tumors (malign mesenchymal tumor, squamous cell carcinoma of the tongue, non-Hodgkin lymphoma, and Sézary syndrome) in the breast are presented and discussed with respect to the literature. Detailed clinical history and a multidisciplinary approach are useful in establishing correct diagnosis and preventing unnecessary radical surgery.

Cytologic findings in malignant myoepithelioma: a case report and review of the literature

Background

Myoepithelioma of the breast is a rare tumor and the cytologic features have only been described in one previous report.

Case presentation

The present case comprises a 70 year old woman with a mammographic equivocal and ultrasonographic suspicious lesion. The aspirates were cellular and consisted mainly of single spindle or polymorphic, polygonal cells. The nuclei were generally large, ranging from 2 - > 5 × RBC. Most nuclei had a distinct medium-sized nucleolus. The nuclear outlines were irregular with buds and folds. The chromatin was granular. In the background there was abundant granular metachromatic ground substance and some metachromatic stromal fragments. A few mitotic figures were found. The cytologic diagnosis was suspicious for malignancy and a metaplastic carcinoma where only the non-epithelial component had been aspirated, or a non-epithelial lesion, was suggested.

Macroscopically the tumor was round, seemingly well circumscribed, firm and with a white cut surface. The lesion consisted of spindled and polygonal cells with distinct pleomorphism. There were 6–9 mitoses per high power field (HPF). The tumor infiltrated in the surrounding fatty tissue. On immunohistochemistry, tumor cells were positive for smooth muscle actin, keratin MNF 116 and vimentin. Desmin and S-100 were negative.

Ultrastructurally, there were abundant tonofilaments, including globular filamentous bodies and granulated endocytoplasmic reticulum with many dilated cisterns. The histologic diagnosis was malignant myoepithelioma.

Conclusion

The case mirrors completely the WHO definition and the previous cytological and histological descriptions of malignant myoepitheliomas in the literature which describe a spindle cell population with unequivocal nuclear atypia, metachromatic background substance and mitoses.

[Salivary gland-like tumors of the breast]

A subset of rare benign and malignant breast tumors with and without myoepithelial differentiation are morphologically and histogenetically similar to salivary gland tumors, but may differ in incidence and clinical behavior. The clinicopathological, immunohistochemical, molecular and prognostic features of ten salivary gland-like tumor entities of the breast are discussed and compared with their respective counterparts in the salivary glands.