An epithelial and spindle cell breast tumour of myoepithelial origin. An immunohistochemical and ultrastructural study

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: A case report and review of the literature

Malignant myoepithelioma of the breast is an extremely rare tumor composed entirely or almost entirely of malignant spindle cells with myoepithelial differentiation. Only a limited number of case reports have been descibed to date; therefore the biological behavior and treatment outcomes of this rare tumor have not been clearly determined. Herein, we present a case of a 74-year-old woman who was admitted with inflammatory-like cancer of the breast, presenting with invasion of the chest wall and axillary lymph node metastasis at the time of diagnosis. The histological examination revealed a tumor composed of epithelioid and spindle cells with moderate to marked nuclear atypia, with foci of hemorrhage and necrosis. The tumor cells were immunoreactive for vimentin, p63, p53, CD10, cytokeratin (CK)8/18, CKAE1-3 and S-100. Finally, a diagnosis of myoepithelial carcinoma of the breast was established. Neoadjuvant chemotherapy was first administered and proved to be ineffective. Due to locoregional progression that was associated with the development of an abscess and subsequent excessive bleeding, a palliative mastectomy was performed. Postoperatively, one more cycle of systemic chemotherapy was administered. However, the patient experienced an early relapse to the chest wall and succumbed to septic shock due to persistent local infection. The aggressiveness and chemoresistance of the tumor in this case was consistent with the existing bibliography.

Myoepithelial Carcinoma: A Rare Neoplasm of the Breast

BACKGROUND: Malignant myoepitheliomas of the breast are extremely rare. There has been a limited number of published reports of myoepithelial carcinomas originating from the breast. CASE REPORT: We describe a malignant myoepithelioma of the breast in a 56-year-old woman. Histological examination showed polygonal epithelioid cells and spindle cells with moderate to marked nuclear atypia. Immunohistochemistry showed reactivity in the spindle cells for smooth muscle actin, cytokeratin (AE1/AE3), and p63, indicating a myoepithelial cell lineage of tumor cells. The patient underwent radical surgical excision of the lesion and axillary lymph node dissection. She demonstrated no evidence of recurrence over an 11-month follow-up. CONCLUSIONS: We suggest myoepithelial carcinomas of the breast be managed with appropriate surgical clearance. A multidisciplinary approach is usually required.

Extensive extranodal metastases of basal-like breast cancer with predominant myoepithelial spindle cell differentiation

A differentiation towards myoepithelial cells has been demonstrated in several types of lesions in the breast. These include multifocal myoepitheliomatosis, the rare mixed tumor or pleomorphic adenoma, adenoid cystic carcinoma, adenomyoepithelioma and myoepithelial carcinoma (malignant myoepithelioma). Myoepithelial carcinoma is the only lesion purely composed of myoepithelial cells. All these tumors are benign and/or of low-grade malignancy, with the exception of malignant myoepithelioma. In contrast to the statement of the current World Health Organization (WHO), recent studies have reported that regional and distant metastases may occur in about 50% of pure myoepithelial carcinomas. The presented case of a breast carcinoma with dominant myoepithelial/spindle cell differentiation in a 58-year-old woman is an excellent example to document the highly aggressive biological behavior of this tumor phenotype. Despite an extensive chemotherapy and radiotherapy, the tumor was rapidly progressive, forming a finally exulcerating local tumor relapse and widespread metastases to the myocardium, lungs, liver, kidneys and skin. Similarities in morphology and biological behavior compared to patients with "triple-negative" (hormone receptor and Her2) monophasic sarcomatoid carcinomas and pure spindle cell sarcomas are discussed.

Salivary gland-type tumors of the breast: a spectrum of benign and malignant tumors including "triple negative carcinomas" of low malignant potential

Salivary gland-type neoplasms of the breast are uncommon and comprise numerous entities analogous to that more commonly seen in salivary glands. The clinicopathologic spectrum ranges from benign to malignant but there are important differences as compared with those of their salivary counterpart. In the breast, benign adenomyoepithelioma is recognized in addition to malignant one, whereas in the salivary gland a histologically similar tumor is designated as epithelial-myoepithelial carcinoma without a separate benign subgroup. Mammary adenoid cystic carcinoma is a low-grade neoplasm compared with its salivary equivalent. It is also important to appreciate that in contrast to "triple negative" conventional breast carcinomas with aggressive course, most salivary-type malignant breast neoplasms behave in a low-grade manner. Most of these tumors are capable of differentiating along both epithelial and myoepithelial lines, but the amount of each lineage-component varies from case to case, contributing to diagnostic difficulties. Well established examples of this group include pleomorphic adenoma, adenomyoepithelioma, and adenoid cystic carcinoma. Another family of salivary gland-type mammary epithelial neoplasms is devoid of myoepithelial cells. Key examples include mucoepidermoid carcinoma and acinic cell carcinoma. The number of cases of salivary gland-type mammary neoplasms in the published data is constantly increasing but some of the rarest subtypes like polymorphous low-grade adenocarcinoma and oncocytic carcinoma are "struggling" to become clinically relevant entities in line with those occurring more frequently in salivary glands.

Bilateral synchronous spindle cell, apocrine and scirrhous carcinoma breast cancer in a case or malignant lymphoma

An unusual case of synchronous bilateral breast cancer occurring during combination chemotherapy and radiation to the outside of the breast for malignant lymphoma is reported. Two histologically rare carcinomas, spindle cell carcinoma and apocrine carcinoma, were observed in this case. A 77-year-old woman, who had been treated for stage IIIA non-Hodgkin's lymphoma, developed bilateral breast tumors. Aspiration biopsy cytology findings of the tumor in the left breast showed several clusters of adenocarcinoma cells and some large atypical spindle shaped cells, which suggested spindle cell carcinoma. The cytologic findings of the right breast tumor were highly suggestive of scirrhous carcinoma. A modified radical mastectomy was performed on both breasts. Pathological examination disclosed two separate cancer lesions in the left breast. The lesion which had been detected before the operation, was a spindle cell carcinoma. Another lesion, detected for the first time by pathological examination, was an apocrine carcinoma. The lesion in the right breast was a scirrhous carcinoma. Since non-invasive foci were detected in these three cancer lesions, each lesion was thought to be a primary cancer. All dissected bilateral axillary lymph nodes showed malignant lymphoma. Immuno-histochemistry of the spindle cell carcinoma revealed positive immunoreactivity for cytokeratin, which suggested the epithelial as well as mesenchymal nature of this tumor. Synchronous existence of malignant lymphoma and three independent breast cancers including spindle cell carcinoma and apocrine carcinoma is very rare.

Metaplastic breast carcinomas are basal-like tumours

AIMS

Recently, an immunohistochemical panel comprising antibodies against HER2, oestrogen receptor (ER), epidermal growth factor receptor (EGFR) and cytokeratin (CK) 5/6 was reported to identify basal-like breast carcinomas, as defined by cDNA microarrays. Our aim was to analyse a series of metaplastic breast carcinomas (MBCs) using this panel plus two other basal markers (CK14 and p63) and progesterone receptor (PR), to define how frequently MBCs show a basal-like immunophenotype.

METHODS AND RESULTS

Sixty-five cases were retrieved from the pathology archives of the authors' institutions and reviewed by three of the authors. Immunohistochemistry with antibodies for HER2, ER, EGFR, CK5/6, CK14 and p63 was performed according to standard methods. All but six cases (91%) showed the typical immunoprofile of basal-like tumours (ER- and HER2-, EGFR+ and/or CK5/6+). When CK14 and p63 were added to the panel, two additional cases could be classified as basal-like. The majority of MBCs lacked PR, except 4/19 (21%) carcinomas with squamous metaplasia.

CONCLUSIONS

Our results demonstrate that MBCs show a basal-like phenotype, regardless of the type of metaplastic elements. Moreover, as these neoplasms frequently overexpress EGFR (57%), patients with MBC may benefit from treatment with anti-EGFR drugs.

EGFR amplification and lack of activating mutations in metaplastic breast carcinomas

Metaplastic breast carcinomas are reported to harbour epidermal growth factor receptor (EGFR) overexpression in up to 80% of the cases, but EGFR gene amplification is the underlying genetic mechanism in around one-third of these. In this study, EGFR gene amplification as defined by chromogenic in situ hybridization and protein overexpression was examined in a cohort of 47 metaplastic breast carcinomas. Furthermore, the presence of activating EGFR mutations in exons 18, 19, 20, and 21 was investigated. Thirty-two cases showed EGFR overexpression and of these, 11 (34%) harboured EGFR gene amplification. In addition, EGFR amplification showed a statistically significant association with EGFR overexpression (p < 0.0094) and was restricted to carcinomas with homologous metaplasia. Ten cases, five with and five without EGFR amplification, were subjected to microarray-based CGH, which demonstrated that EGFR copy number gain may occur by amplification of a discrete genomic region or by gains of the short arm of chromosome 7 with a breakpoint near the EGFR gene locus, the minimal region of amplification mapping to EGFR, LANCL2, and SEC61G. No activating EGFR mutations were identified, suggesting that this is unlikely to be a common alternative underlying genetic mechanism for EGFR expression in metaplastic breast carcinomas. Given that metaplastic breast carcinomas are resistant to conventional chemotherapy or hormone therapy regimens and that tumours with EGFR amplification are reported to be sensitive to EGFR tyrosine kinase inhibitors, these findings indicate that further studies are warranted to explore EGFR tyrosine kinase inhibitors as potential therapeutic agents for metaplastic breast carcinomas harbouring amplification of 7p11.2.

Clinical presentation and long-term outcome of pure myoepithelial carcinoma of the breast

INTRODUCTION

Pure myoepithelial carcinoma of the breast is a rare tumour of controversial histogenesis. Little is known about its natural history and long-term outcome following treatment.

METHODS

All patients with pure myoepithelial carcinoma treated at our institution between 1970 and 2001 were studied with respect to pathological features, outcome and prognosis.

RESULTS

Six patients were identified. The median age was 60 (40-66) years and median follow-up was 34.5 months (range 14-76) months. Four tumours were T1 and one was T2 (one tumour size unknown). There were two moderately differentiated and three well-differentiated tumours (grade could not be assessed in one patient). Oestrogen and progesterone receptor could be assessed in five patients and all were negative. Primary treatment was wide local excision with clear radial margins. Lymph node assessment was negative in all patients. One patient received adjuvant radiotherapy. Three patients developed local recurrence at 15, 38 and 50 months and two patients developed distant metastasis at 30 and 79 months. The local recurrences were treated by further excision but two patients developed distant metastasis at intervals of 15 and 26 months, respectively. Two patients have died of the disease and four remain well. The 2-year and 5-year survival was 88% (SE, 6) and 55% (SE, 16), respectively. Large tumour size is a prognostic indicator of poor outcome.

CONCLUSION

Pure myoepithelial carcinoma of the breast adopts an aggressive clinical course with an outcome comparable to poorly differentiated adenocarcinoma of the breast.

Salivary-type neoplasms of the breast and lung

Salivary-type tumors occur in multiple sites in the human body, likely related to a basic structural homology between exocrine glands in these different anatomic areas. This paper reviews these salivary gland tumor types in breast tissue and lung. Salivary-type tumors of both breast and lung are relatively uncommon in comparison to their salivary gland counterparts. This may be attributable in part to lack of familiarity with these tumors in extra-salivary sites, and in part to histologic overlap with other primary and metastatic tumor types. Recognition of these entities is improving as the clinical and pathologic features are better delineated, and tumors are more accurately classified. Prediction of malignant behavior is not always possible in these unusual sites. In some instances, such as adenoid cystic carcinoma, behavior is known to differ considerably from that of analogous primary salivary gland tumors and in other instances there are simply too few reported cases to allow for adequate prognostication. In fact, more recent papers discuss the need to consider a spectrum encompassing benign and malignant lesions, in both breast and lung. Of course, some entities show clear-cut evidence of malignancy with documented potential for metastasis, others show bland features and well-reported benign behavior, and the less well-defined entities reside between these two extremes. The molecular pathology of salivary gland tumors has been reasonably well investigated in that location; however; there are few molecular studies devoted to salivary-type tumors of the breast and lung. This represents a potential area for future growth in further clarifying these tumors and their behavior.

Salivary gland-like tumours of the breast: surgical and molecular pathology

Breast glands and salivary glands are tubulo-acinar exocrine glands that can manifest as tumours with similar morphological features, but that differ in incidence and clinical behaviour depending on whether they are primary in breast or salivary glands. Salivary gland-like tumours of the breast are of two types: tumours with myoepithelial differentiation and those devoid of myoepithelial differentiation. The first and more numerous group comprises a spectrum of lesions ranging from "bona fide" benign (such as benign myoepithelioma and pleomorphic adenoma), to low grade malignant (such as adenoid cystic carcinoma, low grade adenosquamous carcinoma, and adenomyoepithelioma), to high grade malignant lesions (malignant myoepithelioma). The second group comprises lesions that have only recently been recognised, such as acinic cell carcinoma, oncocytic carcinoma of the breast, and the rare mucoepidermoid carcinoma.

Multifocal, nascent, and invasive myoepithelial carcinoma (malignant myoepithelioma) of the breast: an immunohistochemical and ultrastructural study

This report describes the light microscopic (LM), immunohistochemical (IHC), and electron microscopic (EM) features of a multifocal, nascent, and invasive myoepithelial carcinoma of the breast. By LM, the spindle cells disclosed fibrillar acidophilic cytoplasm, mild nuclear atypia, and a low mitotic index. Myoepithelial differentiation was established through IHC (single- and double-labeling techniques) and EM: periductal and infiltrating spindle cells coexpressed total muscle actin, alpha-smooth muscle actin, vimentin, cytokeratin 14, and pankeratin, and their EM features were characteristic of myoepithelial cells, i.e., perinuclear tonofilaments, subplasmalemmal bundles of microfilaments with dense bodies, intermediate junctions, poorly developed desmosomes, pinocytic vesicles, and fragmented external lamina. No invasive epithelial cells disclosed luminal differentiation (by LM, IHC, EM), identifying, thus, this neoplasm as a pure spindle cell myoepithelial carcinoma of the breast.

Malignant adenomyoepithelioma of the breast with malignant proliferation of epithelial and myoepithelial elements: a case report and review of the literature

Malignant adenomyoepithelioma of the breast is a rare lesion characterized by malignant proliferation of epithelial and myoepithelial cells that show characteristic histologic and immunohistochemical features. Eleven cases have been reported, 4 of which showed evidence of distant metastasis. The authors report a case of malignant adenomyoepithelioma in the axillary tail of a 71-year-old woman, one of the oldest patients described so far, and review the literature. Malignancy in the current case was evidenced by the presence of local invasion, high mitotic rate, and severe cytologic atypia. The tumor was associated with adenosis and lobular adenomyoepithelial hyperplasia. Malignant adenomyoepithelioma is a rare neoplasm, diagnosable by light microscopy and immunohistochemistry. To date, it has only been reported in women, who ranged in age from 26 to 76 years. Metastases have only been documented in tumors 2.0 cm in diameter or larger.

Spindle cell carcinoma of the breast: a case report and an immunohistochemical study including p53 and Ki-67 expression

A rare case of spindle cell carcinoma (SpCC) of the breast occurring in a 51-year-old Japanese woman is reported. A firm and well-circumscribed tumor, measuring 9 x 8.5 x 8.5 cm, was located on the upper lateral region of the right breast. Microscopically, the tumor consisted of sheets of both malignant spindle cells and poorly differentiated ductal carcinoma containing squamoid islands with gradual transition to the spindle cell component. The immunocytochemical expression of epithelial markers was recognized in the spindle cells, as well as in the carcinomatous cells. Moreover, the spindle cell component expressed vimentin, alpha-smooth muscle actin and S-100 protein. Ultrastructurally, in addition to the features of adenocarcinoma, squamous or myoepithelial differentiation was confirmed in the spindle cell component. These findings thus suggest an epithelial origin with squamous differentiation and myoepithelial participation in the genesis of SpCC. In a comparative study, the expression of p53 protein and Ki-67 as a proliferation marker in each component of this tumor was also investigated. The mean p53 labeling index (LI) in both the carcinomatous and spindle cell area was similar, however the mean MIB-1 LI in the spindle cell area was significantly higher than that in the carcinomatous area. The results indicate that p53 overexpression is involved in the tumorigenesis of both components in the SpCC, and the spindle cell component shows a higher degree of proliferative activity than the carcinomatous component.

Metaplastic breast carcinoma invading chest wall

Metaplastic breast carcinoma refers to a heterogeneous group of neoplasms in which the typical glandular growth pattern of the tumor undergoes metaplasia, either epithelial or stromal. A 59-year-old woman presented with a breast mass that recurred in 1 year and showed invasion of the chest wall. Histological sections of both the tumor and the recurrence showed a tumor composed predominantly of stromal spindle cells with neoplastic epithelial ducts. Squamous metaplasia was seen in some ducts. Immunohistochemical staining showed positive cytokeratin and epithelial membrane antigen staining of the epithelial cells. Smooth muscle actin, S100, and vimentin were diffusely positive in the stromal cells. Electron microscopy of the original lesion showed cells with squamous epithelial and smooth muscle characteristics, and other cells that formed lumens into which microvilli projected. Electron microscopy of the recurrent lesion showed primarily spindle-shaped cells with abundant tonofilaments in the perinuclear cytoplasm, desmosomes with associated tonofilaments, filaments with focal densities, often aligned parallel with the cell membranes, surface attachment plaques, and fragments of basement membrane. Pinocytotic vesicles were rare. These metaplastic cells are derived from myoepithelial cells which are multipotential and able to differentiate into epithelial or stromal cells.

Intralobular growth of myoepithelial cell carcinoma of the breast

Two cases of intralobular carcinoma of the breast showing myoepithelial cell differentiation are reported. One was an in situ lesion localized within a fibroadenoma; the second was predominantly in situ, but areas of invasion were present. The neoplastic cells had round to ovoid nuclei and were polygonal to spindle in shape displaying glycogen rich clear cytoplasm. Alpha-smooth muscle actin was present in the cytoplasm of the neoplastic cells in both cases. In one case the same cells displayed cytoplasmic microfilaments at electron microscopic level. Intralobular growth of neoplastic myoepithelial cells has never been described in the literature, and this line of differentiation has to be added to the endocrine and apocrine features occasionally observed in in situ lobular carcinomas of the breast.

Adenomyoepithelioma of the breast: report of a case initially examined by fine-needle aspiration

This report describes the morphologic features of an adenomyoepithelioma of the breast that was first examined by fine-needle aspiration. On retrospective review of the cytology, the stromal elements of this adenomyoepithelioma showed extensive metachromasia on Diff-Quik stain, had elongated nuclei, and on Papanicolaou stain showed elongated, pale, wispy cytoplasm. Clusters of stromal cells were usually intimately associated with epithelial elements. While the main differential consideration, cystosarcoma phylloides, can show similar features, it may be possible to distinguish the two lesions in some instances.

Immunohistochemistry with keratin, vimentin, desmin, and alpha-smooth muscle actin monoclonal antibodies in canine mammary gland: normal mammary tissue

Normal canine mammary gland tissue was studied immunohistochemically with monoclonal antibodies (MoAbs) directed against various human keratin types, vimentin, desmin, and alpha-smooth muscle actin. Both ductal and alveolar luminal cells were immunoreactive with MoAbs recognizing respectively human keratins no. 7, 8, 18 and 19. In addition, some ductal luminal cells were labelled with a keratin 4 and a keratin 10 MoAb. Basal/myoepithelial cells were immunoreactive only with MoAbs directed against keratin 14, keratins 14 and 17, and alpha-smooth muscle actin. The vimentin MoAb merely labelled solitary loose intraluminal cells representing macro-phages or sloughed epithelial cells. These findings correspond largely to observations made in human breast tissue.

Immunohistochemistry with keratin, vimentin, desmin, and alpha-smooth muscle actin monoclonal antibodies in canine mammary gland: benign mammary tumours and duct ectasias

Duct ectasias (n = 2) and different types of benign canine mammary tumours (n = 19) were studied immunohistochemically with monoclonal antibodies (MoAbs) directed against various human keratin types (K), alpha-smooth muscle actin, vimentin, and desmin. In the duct ectasias and in most tumours the epithelial structures revealed an inner and outer cell layer. The inner cell layer was characterized by labelling with K 7, 8, 18, 19 and mostly also with K 4 and/or K 10 MoAbs. The outer cell layer was almost invariably labelled by K 14, K 14 and 17, and a-smooth muscle actin MoAbs. The labelling patterns of both duct ectasias and tumours corresponded largely to the patterns observed in normal mammary gland tissue, although a more distinct heterogeneity was seen. Tumours histomorphologically assumed to be of a myoepithelial origin did not show immunohistochemical features of myoepithelial cells. The myoepithelial nature of the vast majority of spindle-shaped cells present in the adenomas of the complex type and in the fibroadenomas of the benign mixed type could not be confirmed immunohistochemically. These cells, however, unequivocally expressed vimentin, suggesting proliferation of stromal cells in these tumours, which in the fibroadenomas of the benign mixed type may show metaplasia to bone or cartilage. In the duct ectasias and in some tumours, a fraction of elongated stromal cells, probably representing myofibroblasts, was labelled with the alpha-smooth muscle actin MoAb.

The biology of breast tumor progression. Acquisition of hormone independence and resistance to cytotoxic drugs

Many breast tumors appear to follow a predictable clinical pattern, being initially responsive to endocrine therapy and to cytotoxic chemotherapy but ultimately exhibiting a phenotype resistant to both modalities. Using the MCF-7 human breast cancer cell line as an example of an 'early' phenotype (estrogen and progesterone receptor positive, steroid responsive, low metastatic potential), we have isolated and characterized a series of hormone-independent but hormone-responsive variants (MIII and MCF7/LCC1). However, these variants remain responsive to both antiestrogens and cytotoxic drugs (methotrexate and colchicine). MIII and MCF7/LCC1 cells appear to mimic some of the critical aspects of the early progression to a more aggressive phenotype. An examination of the phenotype of these cells suggests that some hormone-independent breast cancer cells are derived from hormone-dependent parental cells. The development of a hormone-independent phenotype can arise independently of acquisition of a cytotoxic drug resistant phenotype.

Bronchioloalveolar adenocarcinoma with myoepithelial cells

A unique variant of papillary lung carcinoma in a 58-year-old woman with both Clara cell and myoepithelial components is reported. The tumor was characterized by the presence of glandular spaces lined by two cell layers. The superficial (luminal) layer was made up of columnar cells with ultrastructural and immunohistochemical features of Clara cells, and occasional interspersed type 2 pneumocytes. The cells of the basal layer possessed ultrastructural and immunohistochemical features of myoepithelial cells. Myoepithelial cells have not previously been reported in a bronchioloalveolar adenocarcinoma.