Antibodies to Novel Myoepithelium-Associated Proteins Distinguish Benign Lesions and Carcinoma in Situ From Invasive Carcinoma of the Breast:

Is it ductal carcinoma in situ with microinvasion or "Ductogenesis"? The role of myoepithelial cell markers

Mammary myoepithelial cells have been under-recognized for many years since they were considered less important in breast cancer tumorigenesis compared to luminal epithelial cells. However, in recent years with advances in genomics, cell biology, and research in breast cancer microenvironment, more emphasis has been placed on better understanding of the role that myoepithelial cells play in breast cancer progression. As the result, it has been recognized that the presence or absence of myoepithelial cells play a critical role in the assessment of tumor invasion in diagnostic breast pathology. In addition, advances in screening mammography and breast imaging has resulted in increased detection of ductal carcinoma in situ and consequently more diagnosis of ductal carcinoma in situ with microinvasion. In the present review, we discuss the characteristics of myoepithelial cells, their genomic markers and their role in the accurate diagnosis of ductal carcinoma in situ with microinvasion. We also share our experience with reporting of various morphologic features of ductal carcinoma in situ that may mimic microinvasion and introduce the term of ductogenesis.

Microinvasive Carcinoma of the Breast

Microinvasive carcinoma of the breast is a controversial entity for a number of reasons. First, the identification of areas of microinvasion is often problematic for the pathologist. Second, varying definitions for this lesion have been used by different authors. Third, studies of microinvasive carcinoma have been limited by small patient numbers. As a consequence, there are differences of opinion regarding both the clinical significance of microinvasion and the management of patients with this lesion. The purpose of this article is to review the controversies surrounding microinvasive carcinoma of the breast.

Intracystic Papillary Carcinoma in a Man with Gynecomastia

Male breast cancer is a rare disease in the male breast whereas gynecomastia is quite common. An elevation of the estrogen-to-androgen ratio increases the risk of both of these diseases. However, a connection between gynecomastia and subsequent breast cancer development is controversial and unclear. Imaging studies including mammography and ultrasound provide valuable information in leading to a correct diagnosis. Traditionally, intracystic papillary carcinoma, also known as encapsulated papillary carcinoma, has been considered a form of ductal carcinoma in situ. Recent immunohistochemical studies, demonstrating an absence of myothelium, in many cases would be more compatible with the diagnosis of invasive malignancy. However, intracystic papillary carcinoma holds a favorable prognosis with local therapy alone. We report a case of intracystic papillary carcinoma in a male patient with long-standing gynecomastia diagnosed eight years prior by mammography. The patient presented with a breast lump on both occasions. Current work-up consisted of both mammography and ultrasound. Ultrasound provided key information revealing a complex mass requiring further evaluation. Ultrasound-guided core needle biopsy revealed intracystic papillary carcinoma with confirmation upon surgical excision.

Fine-needle aspiration of superficial myxoid neurofibroma in the region of the breast

Myxoid neurofibromas are benign spindle cell tumors of perineural cell origin with a broad pathologic differential diagnosis, which includes myxoma, myxoid liposarcoma, myxoid dermatofibrosarcoma protuberans, and low-grade fibromyxoid sarcoma. We present an unusual case of superficial myxoid neurofibroma in the region of the breast that underwent pre-operative fine-needle aspiration (FNA). The differential diagnosis for a myxoid subcutaneous lesion should include myxoid neurofibroma when myxoid material is encountered in an otherwise hypocellular FNA.

Use of CD10 as a marker of canine mammary myoepithelial cells

CD10 is an important cell marker in the diagnosis of acute lymphoblastic leukaemia and of breast myoepithelial (ME) cells in humans. The objective of this study was to assess the value of CD10 as a marker of canine ME cells using immunohistochemistry on routinely processed normal, dysplastic and neoplastic mammary tissue. Five different CD10 positive cell types were identified on the basis of cell morphology, pattern of immunoreactivity, and on the co-expression of additional cell lineage-specific markers. Type 1 cells were typical fusiform cells with a ME cell phenotype (calponin- and cytokeratin [CK] 14-positive, CK8/18-negative). Type 2 cells were typical or atypical polyhedral cells with a luminal epithelial (LE) cell phenotype (calponin- and CK14-negative, CK8/18-positive). Type 3 cells had a type 1 phenotype with variable morphology, and type 4 were atypical neoplastic cells with a mixed ME/LE phenotype. Type 5 cells were typical fusiform cells with a stromal phenotype. Type 1 cells were considered normal ME cells and were found in all sample types; type 2 cells were considered normal or neoplastic LE cells and were also found in all sample types; types 3 and 4 cells were restricted to tumour samples and to malignant tumours, respectively, and type 5 cells were found in all sample types, although predominantly in neoplastic tissue. The findings indicate that the CD10 antigen is a sensitive (although not specific) marker of canine ME cells in normal, dysplastic and neoplastic mammary tissue. Differences in the distribution and staining intensity of CD10-positive cells suggest a number of potential roles for this protein in the pathogenesis of canine mammary neoplasia.

Morphological and immunohistochemical observations on leiomyoma of the ventral ligament of the oviduct of the hen

Leiomyomas of the ventral ligament (LVLs) of the oviduct from 2-year-old spent layers were examined. These tumours can be present either as single large masses or as multiple smaller nodules. The most common site of origin of the tumours was the centre of the free margin of the ventral ligament, but some small tumours were observed at the insertion of this ligament into the magnum of the oviduct. Most samples were highly vascular and some blood vessels within the tumours had vacuolation of the smooth muscle cells. These findings suggest that the proliferative processes leading to LVLs may include transformation of the blood vessels of the ventral ligament. Immunohistochemically, the tumour cells expressed vimentin, α-smooth muscle actin, desmin and heavy-caldesmon. These avian leiomyomas have been proposed as a model for similar tumours in other species.

Calponin expression and myoepithelial cell differentiation in canine, feline and human mammary simple carcinomas

Calponin is a 34-kDa smooth muscle-specific protein that has been shown to be a highly sensitive marker of myoepithelial cells in canine, feline and human mammary tissue and tumours. The expression of calponin was studied in 15 canine, 32 feline and 28 human simple mammary carcinomas using a monoclonal mouse antihuman calponin antibody and the avidin-biotin peroxidase complex (ABC) immunohistochemical technique. Calponin expression was compared with the expression of cytokeratin 14, a marker of normal mammary myoepithelial cells in the three species. Four different types of calponin-positive cells were identified: (1) Type 1: cytokeratin-14-positive pre-existing myoepithelial cells forming a continuous layer with images of focal disruptions; (2) Type 2: cytokeratin-14-positive isolated nests of fusiform, polygonal or round cells without atypia; (3) Type 3: cytokeratin-14-positive atypical cells indistinguishable from non-reactive atypical cells, which should have never been detected in haematoxylin and eosin-stained sections and (4) Type 4: cytokeratin-14-negative stromal fusiform cells around the neoplastic growth or cell nests, identified as myofibroblasts. Calponin-negative and cytokeratin-14-positive atypical neoplastic cells were observed in three canine, 28 feline and two human carcinomas. The latter were indicative of altered expression of high-molecular-weight cytokeratins in luminal epithelial-type simple carcinomas. Our findings show that calponin is a good marker of myoepithelial cell differentiation in feline, human and, particularly, canine simple carcinomas. The high number (six out of 15) of canine tumours with type 3 cells points to the need of both introducing calponin examination in the routine diagnostic schedule and performing further studies on its prognostic significance.

Immunohistochemical staining of papillary breast lesions

The separation of ductal papilloma from intraductal papillary carcinoma of the breast on hematoxylin and eosin stained sections often presents diagnostic difficulty. Immunohistochemical staining is often employed in diagnosis, historically with smooth muscle actin (SMA). In this study, the staining characteristics of a panel of myoepithelial markers (calponin, p63, P-cadherin), were compared with SMA, and the epithelial expression of CD44s was assessed in 99 papillary lesions. SMA, calponin, and p63 demonstrated myoepithelial cells in 61%, 63%, and 65% of papillary lesions, respectively. However, specificity was quite variable. Calponin-stained stromal myofibroblasts (35% of cases), vessel pericytes (92%), and endothelial cells (69%), though each to a lesser degree than SMA. Calponin also showed cross reactivity with epithelium in 18% of cases. p63 was almost completely restricted to myoepithelial cell nuclei, and did not stain vascular smooth muscle or myofibroblasts. However, p63 stained the epithelial component in one papillary carcinoma, a basal layer of cells in 1 biphasic invasive carcinoma, and the cytoplasm in 1 case. P-cadherin stained both epithelial and myoepithelial cells. The epithelial expression of CD44s and did not distinguish papillomas from papillary carcinomas. Thus, P-cadherin and CD44s are not useful in the characterization of papillary lesions. Given increased specificity as compared with SMA, the combination of p63 and calponin is recommended for analysis of breast papillary lesions.

Immunophenotypic overlap between adenoid cystic carcinoma and collagenous spherulosis of the breast: potential diagnostic pitfalls using myoepithelial markers

Adenoid cystic carcinoma of the breast is a rare neoplasm whose cribriform architecture may mimic invasive cribriform carcinoma, cribriform ductal carcinoma in situ, and collagenous spherulosis. The diagnosis may be even more challenging in needle core biopsies. Immunohistochemical expression of p63 and c-kit distinguishes adenoid cystic carcinoma from invasive cribriform carcinoma and ductal carcinoma in situ. A formal comparison of the immunophenotype of adenoid cystic carcinoma to collagenous spherulosis has not been reported. Of concern is the overlap in myoepithelial markers between these two entities. Both may express S100, smooth muscle actin, and p63. This overlap may cause diagnostic confusion yet is under-emphasized in the literature. The expression profile of newer myoepithelial markers has not been studied in this setting. We evaluated smooth muscle actin, p63, calponin, smooth muscle myosin heavy chain, as well as c-kit, in nine cases of cribriform pattern adenoid cystic carcinoma of the breast in comparison to 12 cases of collagenous spherulosis. Both entities strongly expressed p63 and smooth muscle actin; in adenoid cystic carcinoma, the basaloid myoepithelial-like tumor cells expressed these markers, but the ductular epithelial cells did not. Neither calponin nor smooth muscle myosin heavy chain was expressed in adenoid cystic carcinoma but both were strongly expressed in collagenous spherulosis. Whereas the ductular epithelial cells of adenoid cystic carcinoma were positive for c-kit in all cases, collagenous spherulosis was negative for c-kit. Positive p63 expression by a cribriform breast lesion is not sufficiently specific to confirm a diagnosis of adenoid cystic carcinoma. A broader panel that includes calponin or smooth muscle myosin heavy chain and c-kit is required to exclude collagenous spherulosis in settings in which the distinctive morphologic features that separate these entities are not conspicuously present. Reliance on p63 or smooth muscle actin alone poses a potential diagnostic pitfall in evaluating cribriform breast lesions.

Intracystic papillary carcinomas of the breast: a reevaluation using a panel of myoepithelial cell markers

Intracystic papillary carcinomas (IPC) of the breast have traditionally been considered to be variants of ductal carcinoma in situ (DCIS). However, it is not clear if all lesions categorized histologically as IPC are truly in situ carcinomas, or if some such lesions might represent circumscribed or encapsulated nodules of invasive papillary carcinoma. Given that the demonstration of a myoepithelial cell (MEC) layer around nests of carcinoma cells is a useful means to distinguish in situ from invasive carcinomas of the breast in problematic cases, assessment of the presence or absence of a MEC layer at the periphery of the nodules that comprise these lesions could help resolve this issue. We studied the presence and distribution of MEC at the periphery of the nodules of 22 IPC and, for comparison, 15 benign intraductal papillomas using immunostaining for 5 highly sensitive markers that recognize various MEC components: smooth muscle myosin heavy chain, calponin, p63, CD10, and cytokeratin 5/6. All 22 lesions categorized as IPC showed complete absence of MEC at the periphery of the nodules with all 5 markers. In contrast, a MEC layer was detected around foci of conventional DCIS present adjacent to the nodules of IPC. Furthermore, all benign intraductal papillomas, including those of sizes comparable to those of IPC, showed a MEC layer around virtually the entire periphery of the lesion with all 5 MEC markers. In conclusion we could not detect a MEC layer at the periphery of the nodules of any of 22 lesions categorized histologically as IPC. One possible explanation for this observation is that these are in situ lesions in which the delimiting MEC layer has become markedly attenuated or altered with regard to expression of these antigens, perhaps due to their compression by the expansile growth of these lesions within a cystically dilated duct. Alternatively, it may be that at least some lesions that have been categorized as IPC using conventional histologic criteria actually represent circumscribed, encapsulated nodules of invasive papillary carcinoma. Regardless of whether these lesions are in situ or invasive carcinomas, available outcome data indicate that they seem to have an excellent prognosis with adequate local therapy alone. Therefore, we believe it is most prudent to continue to manage patients with these lesions as they are currently managed (ie, similar to patients with DCIS) and to avoid categorization of such lesions as frankly invasive papillary carcinomas. Given our observations, we favor the term "encapsulated papillary carcinoma" over "intracystic papillary carcinoma" for circumscribed nodules of papillary carcinoma surrounded by a fibrous capsule in which a peripheral layer of MEC is not identifiable.

p63 and CD10: Reliable Markers in Discriminating Benign Sclerosing Lesions From Tubular Carcinoma of the Breast?

The immunohistochemical detection of myoepithelial cells in benign sclerosing lesions of the breast is useful in distinguishing them from tubular carcinoma. So far, this detection has been carried out using antibodies against cytoskeletal proteins, such as alpha-smooth muscle actin (1A4) and calponin. However, the specificity of these markers has been questioned since they may be expressed in stromal myofibroblasts and vascular smooth muscle. Recently, two novel myoepithelial markers have been described: the nuclear protein p63, a member of the p53 family, and the surface antigen CD10, also known as common acute lymphoblastic leukemia antigen (CALLA). The authors assessed the use of p63 and CD10 in the differential diagnosis between benign sclerosing lesions, such as sclerosing adenosis and radial scar, and tubular carcinoma, in comparison to the traditional myoepithelial markers 1A4 and calponin. p63, CD10, 1A4, and calponin were expressed in myoepithelial cells of all benign lesions and were consistently negative in all cases of tubular carcinoma. In contrast to cytoskeletal proteins, p63 and CD10 were mostly confined to myoepithelial cells and thus were more specific than the traditional counterparts. However, 1A4 was more intensely expressed and more reproducible than the novel markers. In conclusion, p63 and CD10 may be used as a complement to 1A4 in distinguishing benign sclerosing lesions from tubular carcinoma of the breast.

Myoepithelial cell cocktail (p63+SMA) for the evaluation of sclerosing breast lesions

Sclerosing breast lesions may sometimes mimic the appearance of infiltrating carcinoma due to the entrapment of ductular structures in a fibrotic core. The immunohistochemical detection of the outer myoepithelial cell layer that is indicative of a non-infiltrating lesion is a valuable clue for the diagnosis of such ambiguous cases. The myoepithelial cell markers smooth muscle actin (SMA) and p63 are most commonly used since their specificity and sensitivity are well established. However, recent studies have indicated that some morphologically distinct myoepithelial cells fail to stain for SMA and that p63 positivity can be rarely expressed by a subset of malignant epithelial cells. Moreover, SMA can also be positive in stromal myofibroblastic cells and normal vessels that can be found close to the entrapped ductules and might be erroneously interpreted as myoepithelial cells. In this study, we used a double-immunolabeling technique combining both SMA and p63 antibodies (myoepithelial cell cocktail), in order to investigate whether this technique is advantageous over either marker used alone, in diagnosing sclerosing breast lesions. Our results indicate that p63 alone is not a useful myoepithelial cell marker if applied in large sclerosing breast lesions, however, in smaller lesions it is still of high value. On the contrary, SMA proved significantly useful in the evaluation of myoepithelial cells in larger but not in smaller complex sclerosing lesions. The myoepithelial cell cocktail has a staining sensitivity identical to that of SMA. Nevertheless, in a certain number of cases the cocktail might be useful in differentiating myoepithelial cells from stromal myofibroblasts or vascular smooth muscle cells due to the false impression of a higher staining intensity of the cocktail resulting from the expression of both nuclear and cytoplasmic/membranous antibodies that occupy a wider area of the cell under control.

Diagnostic utility of p75 neurotrophin receptor (p75NTR) as a marker of breast myoepithelial cells

We evaluated the low affinity neurotrophin receptor (p75NTR) as a marker of breast myoepithelial cells. Immunohistochemical staining for p75NTR was performed on paraffin sections of 122 malignant breast lesions, 28 benign lesions and the adjacent normal breast tissue. The staining pattern was compared to those of myosin heavy chain and p63. p75NTR immunostain was consistently positive and compatible with p63 and myosin immunoreactivity in the myoepithelial cells of the normal mammary gland, benign breast lesions (six usual ductal hyperplasias, six specimens with sclerosing adenosis, eight intraductal papillomas, six fibroadenomas), and carcinoma in situ (18 ductal carcinomas in situ, two noninvasive papillary carcinomas, two lobular carcinomas in situ). The luminal cells were negative for p75NTR, but rare positive cells were noticed in the solid areas of some of the usual ductal hyperplasias. Four of 64 invasive ductal carcinomas (6%) and all metaplastic carcinomas (n = 3, 100%) showed a variable degree of p75(NTR) positivity. No p75NTR expression was found in the malignant cells in all in situ carcinomas, invasive lobular carcinomas (n = 11), tubular carcinomas (n = 10), invasive papillary carcinomas (n = 6), mucinous carcinomas (n = 4), and medullary carcinomas (n = 2). No myosin immunoreactivity was seen in the luminal/tumor cells, but p63 pattern of staining in the luminal/tumor cells was quite similar to that of p75NTR. Although significant p75NTR immunoreactivity was noticed in the vessels, nerves, and stromal component of fibroadenomas, no difficulties in the evaluation of the immunostain of myoepithelial cells were encountered. Our study shows that p75NTR is a useful marker for breast myoepithelial cells and can be used to rule out invasive disease as well as to evaluate difficult for diagnosis sclerosing lesions. Our data suggest a role of neurotrophins in the development of fibroepithelial breast tumors and some of the breast carcinomas.

Nodular Mucinosis of the Breast: A Case Report With Pathologic, Ultrasonographic, and Clinical Findings and Review of the Literature

Nodular mucinosis is an extremely rare breast lesion. This benign mass usually presents clinically as a poorly circumscribed, subareolar, myxoid mass in young female patients. We report a case of this rare breast lesion and discuss its clinical, radiologic, and histopathologic features. A 21-year-old white woman presented with a mass in the left breast of 6 months' duration. She had never been pregnant or had any history of breast feeding, surgery, trauma, or use of exogenous hormones or a family history of breast cancer. Clinical breast examination demonstrated a 1 cm “rubbery” mass directly under and continuous with the left nipple. The skin that covered the mass had an edematous and irregular appearance without erythema or drainage from the nipple. Ultrasonography demonstrated a 1-cm, nonintraductal, circumscribed, homogeneous, isoechoic mass that was continuous or part of the base of the left nipple. The mass was smooth, with a thin echogenic rim. Doppler flow showed some vascularity. These findings suggested a benign breast lesion, including a fibroadenoma or nipple adenoma. Despite reassurance, the patient desired excision of the lesion. Gross examination revealed a nodular, rubbery-firm, ovoid, pink, polypoid mass that measured 1.5 × 0.9 × 0.8 cm. Microscopic examination showed a well-circumscribed tumor with a nodular appearance, which consisted of an accumulation of pink myxoid tissue and contained spindle cells with bland-appearing nuclei, no mitosis, and mild cellularity. The pink myxoid tissue was stained with Hale colloidal iron and Alcian blue. The Alcian blue stain was removed by pretreatment with hyaluronidase. The spindle cells stained with vimentin and smooth muscle actin; however, they did not express smooth muscle myosin or cytokeratin. This report presents and discusses the pathologic, ultrasonographic, and clinical findings of this rare entity.

Current Practical Applications of Diagnostic Immunohistochemistry in Breast Pathology

In recent years, immunohistochemistry has assumed an increasingly prominent role in diagnostic breast pathology. Immunohistochemistry is now frequently used in the evaluation of many epithelial proliferations of the breast. Common applications include the use of myoepithelial markers to evaluate for stromal invasion, E-cadherin to distinguish between ductal and lobular neoplasia, high molecular weight cytokeratins to differentiate usual ductal hyperplasia from ductal carcinoma in situ, immunohistochemical profiles to characterize site of origin of metastatic carcinomas, and cytokeratin stains to detect metastases in sentinel lymph nodes. Recent advances, practical considerations, and potential pitfalls in the use of immunohistochemistry in these five diagnostic categories are discussed herein.

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.

Immunohistochemical distinction of invasive from noninvasive breast lesions: a comparative study of p63 versus calponin and smooth muscle myosin heavy chain

Identification of myoepithelial cells using antibodies to cytoskeletal proteins, such as smooth muscle myosin heavy chain (SMM-HC) and calponin, can play an important role in distinguishing invasive carcinoma from its histologic mimics. However, antibodies to these proteins may also cross-react with stromal myofibroblasts and vascular smooth muscle cells. It has recently been demonstrated that myoepithelial cells express the nuclear protein, p63, a member of the p53 gene family. We compared the patterns of reactivity of antibodies with p63, calponin, and SMM-HC on 85 breast lesions, including 11 cases of sclerosing adenosis, 33 cases of ductal carcinoma in situ, including 10 that showed microinvasion, 6 cases of lobular carcinoma in situ, and 35 cases of infiltrating ductal carcinoma. All three antibodies were positive on the vast majority of myoepithelial cells in all cases. A small minority of cases showed focal gaps in the revealed myoepithelial cell layer, reflected in discontinuous positive immunostaining around noninvasive epithelial nests (including ductal carcinoma in situ). No case showed p63 expression by myofibroblasts or vascular smooth muscle cells, whereas myofibroblasts expressed, in 8% and 76% of cases, SMM-HC and calponin, respectively. Although no tumor cell reactivity was noted with antibodies to calponin or SMM-HC, tumor cells in 11% of cases showed at least focal p63 expression. And although antibodies to p63 offer excellent sensitivity and increased specificity for myoepithelial detection relative to antibodies to calponin and SMM-HC, they have the following diagnostic limitations: 1) they occasionally demonstrate an apparently discontinuous myoepithelial layer, particularly around ductal carcinoma in situ, and 2) they react with a small but significant subset of breast carcinoma tumor cells. p63 may represent a myoepithelial marker that can complement or replace SMM-HC and/or calponin in the analysis of difficult breast lesions.

Immunocytochemical expression of epidermal growth factor receptor in myoepithelial cells of the breast

The immunohistochemical expression and distribution of epidermal growth factor receptor (EGFr) in mammary myoepithelial cells (MECs) in normal tissue, benign epithelial proliferative lesions, and in situ carcinoma was performed. Results of the current study demonstrated that MECs stained constantly and strongly for EGFr, creating an outer continuous ring surrounding the epithelium of ducts and acini in healthy, in proliferative epithelial lesions, and in in situ carcinoma, both of ductal and lobular type. Foci of microinvasion were easily appreciated for the complete loss of EGFr immunostaining. Epidermal growth factor receptor expression in normal epithelia ranged from negative to weakly positive; it was positive in hyperplasia, whereas it was not constantly negative in in situ carcinoma. In conclusion, immunohistochemical staining for EGFr is diagnostically useful for MEC identification. The specific EGFr in MECs leads the authors to suggest that its expression may be related to the recently recognized high-specialized paracrine function by which the MECs exert the natural mechanical and functional role in the juxtaposition between epithelium and stoma.

Immunolocalization of the smooth muscle-specific protein calponin in complex and mixed tumors of the mammary gland of the dog: assessment of the morphogenetic role of the myoepithelium

The immunohistochemical expression of the smooth muscle-specific protein calponin was studied to assess the contribution of myoepithelial cells to the histogenesis of spindle cells of complex and mixed tumors of the mammary gland of the dog and the origin of cartilage and bone in mixed tumors. Formalin-fixed tissues from 55 benign and malignant tumors (49 also containing surrounding normal mammary gland) were evaluated. Periacinar and periductal myoepithelial cells of all the 49 normal mammary glands were diffusely stained by the anti-human calponin monoclonal antibody. Calponin was found in 53 (98%) of the tumors studied, reacting with the myoepithelium-like cells of 86% of benign tumors and their remnants in 85% of malignant tumors. Five different types of calponin-immunoreactive myoepithelial cells were identified: hypertrophic myoepithelial cells. fusiform cells, stellate myoepithelial cells, rounded (myoepithelial) cells, and chondroblasts. Differences in staining intensity and staining pattern among these five types of cells suggested a transition of myoepithelial cells to chondroblasts. Stromal myofibroblasts also showed calponin immunoreactivity, but they did not react with a cytokeratin 14 monoclonal antibody, which recognizes myoepithelial cells in mammary gland. Calponin appears to be a very sensitive marker of normal and neoplastic myoepithelium in the canine mammary gland, and its identification in different cell types of complex and mixed tumors of the mammary gland of the dog suggests a major histogenetic role for myoepithelial cells.

p63, a p53 homologue, is a selective nuclear marker of myoepithelial cells of the human breast

Myoepithelial cells (MCs) constitute the basal cell layer of normal mammary epithelia, and their identification is of particular diagnostic value because they are retained in most benign lesions while being lost in malignancy. Several MC immunocytochemical markers are currently available for diagnostic purposes, with special reference to smooth muscle-related antigens. p63 is a member of the p53 gene family, and its germline mutations are associated with severe mammary developmental defects in both rodents and humans. Different p63 isoforms have been identified, some of which (DeltaNp63) are preferentially expressed in the epithelial basal cells of different organs and have been considered as possible markers of stem cells/reserve cells. We investigated immunohistochemically 384 samples of normal and diseased human breast, including 300 invasive carcinomas, using four antibodies recognizing all p63 isoforms, or the DeltaNp63 isoforms. Twenty cytologic specimens were also investigated. Furthermore, snap-frozen tissue samples from three fibroadenomas and 10 invasive ductal carcinomas with their paired non-neoplastic tissues and three corresponding lymph node metastases were evaluated for the expression of p63 mRNA by RT-PCR. In normal breast tissue p63 immunoreactivity was confined to the nuclei of MCs. In all benign lesions p63-immunoreactive cells formed a continuous basal rim along the epithelial structures. Stromal cells, and in particular myofibroblasts, were consistently unreactive. Adenomyoepitheliomas showed nuclear staining in most neoplastic cells. A peripheral rim of p63-immunoreactive cells was retained surrounding lobular and ductal carcinoma in situ, although it was discontinuous as opposed to the normal structures. Invasive breast carcinomas were consistently devoid of nuclear p63 staining, with the exception of the two adenoid-cystic carcinomas, of the two ductal carcinomas with squamous metaplasia, and of 11 (4.6%) ductal carcinomas not otherwise specified, showing p63 immunoreactivity in a minor fraction (5-15%) of the neoplastic cells. In comparison with other MC markers, p63 was the most specific, being restricted exclusively to MCs, whereas antibodies to smooth muscle actin and, to a lesser extent, calponin also decorated stromal myofibroblasts. In the cytologic preparations p63 immunoreactivity was a consistent feature of "naked nuclei" and of a subset of cells surrounding benign epithelial clusters. RT-PCR experiments with primers specific for different p63 isoforms documented that normal tissues and fibroadenomas preferentially expressed the DeltaNp63 isoforms. Our study demonstrates that in normal and pathologic breast tissues MCs consistently express the DeltaNp63 isoforms. We suggest p63 as a reliable, highly specific, and sensitive MC marker in both histologic and cytologic preparations. Furthermore, because p63 immunoreactivity in adult epithelia is normally restricted to progenitor cells, it can be speculated that it might be a clue for the identification of the still elusive breast progenitor cells.

Use of a novel marker, calponin, for myoepithelial cells in fine-needle aspirates of papillary breast lesions

Benign and malignant papillary lesions of the breast (PBL) can be difficult to distinguish in fine-needle aspirates (FNA). This study evaluates the use of smooth muscle actin (SMA) and a new smooth muscle-specific protein, calponin, for identifying myoepithelial cells (MEC) by immunohistochemical methods in paraffin-embedded cell blocks of FNA of PBL. Formalin-fixed, paraffin-embedded cell blocks of 40 cases of PBL were stained using SMA and calponin, steam heat-induced epitope retrieval, and an avidin biotin-complex technique. Staining was evaluated in MEC, epithelial, and stromal cells. The diagnosis of benign vs. malignant papillary lesion was made by using cytomorphological criteria and the presence/absence of MEC in the cell block. These results were compared to the original cytologic and subsequent histologic diagnoses. Of 40 cases of FNA diagnosed as PBL, there were 27 intraductal papillomas (IP), 6 papillary lesions with atypical features (PLAF), and 7 papillary carcinomas (PC). In all of the IP, MEC stained both with SMA and calponin. None of the PC cases was positive for MEC with calponin, and 2 out of 7 cases were weakly positive by SMA. In 6 cases of PLAF, 2 were negative for MEC, both by SMA and calponin, and a malignant papillary lesion was confirmed by histology. The remaining 4 cases were positive for MEC with both markers and were confirmed to be benign by histology. SMA stained stromal cells strongly in all of the cases where stroma was present (18 of a total of 40 cases of PBL), while calponin stained stroma focally in only 7 cases. More than half of all cases had nuclear staining of epithelial cells with SMA; calponin did not show any nuclear staining.

Comparative genomic hybridization analysis of myoepithelial carcinoma of the breast

Although there seems to be a common stem cell for the two epithelial cell types in the breast, the vast majority of breast cancers exhibit a luminal phenotype. Pure myoepithelial carcinomas are rare. We report our findings of genetic alterations in these tumors. We have analyzed 10 cases of pure myoepithelial cell carcinomas using laser capture microdissection and comparative genomic hybridization. The mean number of changes was 2.1 (range 0-4), compared with a mean of 8.6 (range 3.6-13.8) in unselected ductal carcinomas. Common alterations included loss at 16q (3/10 cases), 17p (3/10), 11q (2/10), and 16p (2/10), regions also commonly deleted in ductal carcinomas. The single case in which both pure myoepithelial carcinoma and invasive ductal carcinoma was present showed 2 alterations in the myoepithelial tumor (losses at 17p and 17q), whereas the invasive ductal component showed 15 alterations (5 gains and 9 losses), including loss at 17p. The sharing of 17p loss in myoepithelial and ductal carcinoma is consistent with a common stem cell model in the breast. The relatively few genetic alterations in otherwise aggressive neoplasms suggests that myoepithelial tumors may be a good model for the delineation of genes important in breast tumorigenesis.

Immunohistochemical detection of maspin is a useful adjunct in distinguishing radial sclerosing lesion from tubular carcinoma of the breast

Maspin is a recently described member of the serpin family of protease inhibitors that is consistently expressed at high levels in mammary myoepithelial cells. This feature was used in the immunohistochemical evaluation of tubular carcinoma (TC) and radial sclerosing lesion (RSL) of the breast, and compared with other markers of myoepithelial cells. Ten cases of TC and 11 cases of RSL were studied for the expression of maspin, alpha-smooth muscle actin (alpha-SMA), metallothionein (MT), and S-100 protein by immunohistochemistry. Myoepithelial cells stained strongly and diffusely for maspin creating a pattern of an outer continuous ring surrounding the epithelium of tubules of all RSLs. This pattern was absent in all TCs; however, the single-layered epithelium comprising the tubules of two TCs was positive for maspin with a moderate to strong intensity. Myoepithelial cells were not positive for MT in a consistent manner. Benign nonproliferative epithelium stained focally and weakly for maspin in four of 11 cases of RSL and was negative for MT in all 11 cases. Foci of mild to moderate epithelial hyperplasia noted in five of 11 cases of RSL stained diffusely with a weak to moderate intensity for maspin and focally with a strong intensity for MT. alpha-SMA was consistently expressed in myoepithelial cells but also in stromal myofibroblasts and blood vessels, creating a pattern that was less satisfactory than maspin in distinguishing RSL from TC. Immunohistochemical staining for S-100 protein was of no differential diagnostic value. In conclusion, immunohistochemical staining for maspin is diagnostically useful and superior to MT, S-100, and alpha-SMA, in distinguishing RSL from TC. The epithelial immunoreactivity for maspin in two of 10 TCs merits further investigation from a prognostic viewpoint.

Differential Expression of Myoepithelial Markers in Salivary, Sweat and Mammary Glands

Myoepithelial cells (MECs) are contractile elements showing a combined epithelial and smooth muscle phenotype. Among the numerous immunohistochemical markers employed to detect MECs, smooth muscle actin (SMA) is the most widely used. Recently, other markers of smooth muscle differentiation have been demonstrated in MECs, such as calponin, heavy caldesmon (h-caldesmon), and smooth muscle myosin heavy chain (SMM-HC). In the present study normal salivary, mammary, and sweat glands have been studied with four markers of smooth muscle differentiation (SMA, calponin, h-caldesmon, and SMM-HC). The four markers were differentially expressed in the various types of glands. In parotid glands MECs mainly expressed calponin and caldesmon; in submandibular and in cutaneous apocrine and eccrine glands, MECs strongly expressed SMA, calponin, and caldesmon; in minor salivary glands all four markers were equally strongly expressed; and in mammary glands SMA, calponin, and SMM-HC were present both in periductal and periacinar MECs while caldesmon was present in periductal MECs only. In addition to MECs, SMA stained stromal myofibroblasts, sometimes hampering the identification of MECs. Among the other markers, calponin stained only rare stromal myofibroblasts, while caldesmon and SMM-HC were confined to MECs. In conclusion, these latter markers are very useful for identifying MECs. It is suggested that the differential expression of smooth muscle contractile proteins might reflect different functions of MECs in the various sites. Int J Surg Pathol 8(1):29-37, 2000

Immunoreactivity of ductal cells with putative myoepithelial markers: A potential pitfall in breast carcinoma

The identification of an intact layer of myoepithelial cells (MECs) located between epithelial cells and the basal lamina is useful in differentiating benign breast lesions and carcinoma in situ from invasive breast carcinoma. In the present study we used three antibodies considered to be putative markers of MECs (S100 protein, muscle-specific actin [HHF-35], and smooth muscle actin [SMA]) in 100 formalin-fixed, paraffin-embedded histologic sections of breast in an attempt to compare their value in demonstrating MECs in benign breast tissue and breast carcinomas. We concluded that for identifying MECs in benign breast tissue, SMA appears to be the most reliable, followed closely by HHF-35, but S100 is very unreliable for this purpose. In breast carcinoma, all three stains showed variable cross-reactivity with myofibroblasts, being greatest with SMA. A significant number of tumor cells in ductal carcinoma, both intraductal and invasive, stain with these markers and this "cross-reactivity" is extremely high with HHF-35. Thus, immunohistochemistry should be interpreted cautiously in differentiating benign, in situ, and invasive breast neoplasms. The "cross-reactivity" also suggests the possibility of myoepithelial differentiation and/or high actin content of breast tumor cells.

Distribution of calponin and smooth muscle myosin heavy chain in fine-needle aspiration biopsies of the breast

The cell types that may be present in any fine-needle aspiration biopsy (FNAB) of breast include epithelial cells (EC), myoepithelial cells (MEC), bipolar stromal cells (BSC), vascular pericytes/endothelial cells (VPEC), and adipose cells (AC). The recognition of most of these benign cellular elements in aspirates of the breast is relatively straightforward, based on distinct cytomorphologic criteria. However, there is controversy regarding the recognition of MEC because BSC are often referred to as MEC by cytopathologists. It is important to identify MEC in breast aspirates, because their presence has been associated with benign epithelial proliferations. In this study we used immunocytochemical methods on archival cytology slides with antibodies specific for MEC, calponin, and smooth muscle myosin heavy chain (SMMHC), to determine the distribution of MEC in FNAB of the breast and to ascertain the distribution of MEC in in situ and invasive carcinomas. Fifteen benign FNABS of breast and corresponding tissue biopsies were obtained along with 10 malignant FNABS and corresponding excisional breast biopsies from 1989-1993. Calponin and SMMHC antibodies were used on archival alcohol-fixed Papanicolaou-stained direct smears as well as the corresponding tissue sections. The distribution and pattern of positive immunostaining with both antibodies were recorded on the benign elements and the carcinomas for both cytologic and histologic slides. Benign breast tissues demonstrated strong continuous immunostaining for calponin and SMMHC of MEC. The interlobular stromal cells as well as intralobular stromal cells showed no immunostaining with either antibody. In cytologic preparations, MEC staining with calponin and SMMHC appeared as spindle cells between epithelial cells or along the edges of the epithelial groups. The bipolar stromal cells did not stain with either antibody. The tissues with DCIS (ductal carcinoma in situ) often showed the presence of MEC with strong calponin immunostaining, but sometimes the immunostaining was discontinuous or entirely absent around markedly dilated ducts. The SMMHC antibody was invariably negative, with architectural DCIS in dilated ducts. Two cases of DCIS with prominent periductal fibrosis or inflammation were positive for calponin, but the periductal stromal cells were calponin- and SMMHC-negative. Invasive carcinoma was negative for both calponin and SMMHC, but areas of DCIS were often positive in a discontinuous pattern. In conclusion, 1) Benign cellular elements from breast tissue FNAB showed strong continuous decoration of MEC with both calponin and SMMHC. Vascular pericytes and vascular smooth muscle were positive for both antibodies, but these cells were not observed in the FNAB. Benign proliferative epithelium showed no local increase in MEC with either antibody. Bipolar stromal cells in tissue and smears did not stain for MEC antibodies. 2) BSC did not correspond morphologically to MEC, and were not decorated with calponin or SMMHC. 3) Calponin-positive MEC were commonly associated with in situ ductal lesions, although they may at times have been discontinuous or absent entirely. DCIS may be recognized in FNAB by the presence of calponin-positive MEC associated with tumor cell groups. 4) Invasive carcinomas were invariably negative for MEC with these antibodies.

Double immunolabeling with cytokeratin and smooth-muscle actin in confirming early invasive carcinoma of breast

Histopathological identification of invasive breast carcinoma in its earliest phases is fraught with pitfalls. Preinvasive malignant lesions complicated by radial scar, sclerosing adenosis, and lobular cancerization, among other lesions, may simulate invasive carcinoma. Fibrosis, inflammatory reaction, and other stromal changes around in situ carcinoma may mask microinvasive foci on routine stains. Conventional immunohistochemistry to demonstrate basement membrane or myoepithelial cell layer may not, by itself, be unequivocally diagnostic of invasion. We performed a novel double immunoenzyme labeling technique using an avidin-biotin complex peroxidase-diaminobenzidine system for smooth-muscle actin followed by an alkaline phosphatase anti-alkaline phosphatase-new fuchsin system for cytokeratin antigen on formalin-fixed, paraffin-embedded histology sections to evaluate 32 such problematic cases. The initial histologic impression with hematoxylin and eosin staining alone was as follows-first group: microinvasive carcinoma-10; second group: carcinoma in situ--"stromal invasion cannot be ruled out"--15; third group: frankly infiltrating carcinoma of various grades and morphologic types-6. The last group served as positive control for invasion. One fibroadenoma with fine-needle-aspiration-induced artifact simulating stromal invasion was also included. The double immunoenzyme labeling technique imparted a dark brown color to the myoepithelial cells and a vivid red color to the epithelial cells, making individual or loosely cohesive groups of malignant epithelial cells infiltrating the stroma easily detectable, whereas their in situ counterparts were contained within dark brown myoepithelial boundaries. The TNM 1997 definition of pT1mic, i.e., extension of malignant cells in the stroma with no focus measuring >0.1 cm, was followed to classify microinvasion. In the first group, microinvasion was confirmed in six cases but was not demonstrable in four. In the second group, definite invasion was identified in five cases, ruled out in nine, and in one case the suspicion of early invasion could not be entirely ruled out even after double immunoenzyme labeling. Thus, it was possible to render a definite opinion regarding presence or absence of invasion in 24 of 25 (96%) cases diagnosed as or suspected to be microinvasive. The precise and simultaneous elucidation of topography between malignant cells and myoepithelial cells on a single permanent section makes this technique a useful diagnostic tool in the evaluation of those cases of breast carcinoma that exhibit equivocal invasion.

Malignant phyllodes tumor of breast with lung metastases mimicking the primary

We report a case of recurrent malignant phyllodes tumor with liposarcomatous transformation metastasizing to the lung. The unusual feature of this case was that the metastases reproduced the primary tumor and contained ductal structures and elements of sarcoma. The origin of the ductal structures in the lung metastases was confirmed to be from the phyllodes tumor, on the basis of their immunophenotype. The epithelial cells were positive for steroid receptors and GCDFP-15, and the myoepithelial cells were positive for anti-smooth-muscle-specific proteins. We also reevaluated by immunohistochemistry a case of phyllodes tumor previously published by West et al., allegedly containing epithelial structures of supposed breast origin within lung metastases. The epithelial component was shown to consist of entrapped alveolar lining cells.