Apocrine carcinoma-and-malignant myoepithelioma in a dog: a case of simultaneous malignant progression of both luminal epithelium and myoepithelium.

A 9-y-old male Boxer dog developed a mandibular skin tumor, which histologically had a locally invasive growth pattern composed of bilayered structures of inner eosinophilic cuboidal tumor cells and outer clear polygonal tumor cells with cytoplasm containing glycogen granules. Both cell populations gradually changed from low-grade morphologic features to highly anaplastic ones. Immunohistochemically, the eosinophilic tumor cells were positive for cytokeratin 8, a useful marker for luminal epithelial cells. In contrast, the clear tumor cells expressed several myoepithelial markers, including α-smooth muscle actin, p63, and cytokeratin 14. Based on these histologic and immunohistochemical characteristics, we diagnosed this apocrine sweat gland tumor as a carcinoma-and-malignant myoepithelioma with high-grade transformation of both luminal and myoepithelial cells. Our case may be a helpful reference for the histogenesis of carcinoma-and-malignant myoepithelioma, in which both the luminal epithelial and myoepithelial components are malignant.

Solid Carcinoma of the Canine Mammary Gland: a Histological Type or Tumour Cell Arrangement?

Mammary neoplasms are the most frequently diagnosed tumours in female dogs and are classified into various histological types, including solid carcinomas. We proposed a subclassification of solid carcinomas based on morphological and immunohistochemical characteristics, and correlated the subtypes with prognostic factors. A total of 135 cases of solid mammary carcinoma were selected from 3,400 canine mammary neoplasms in the archives of the Laboratory of Comparative Pathology, Institute of Biological Sciences, Federal University of Minas Gerais, Brazil. Epidemiological and survival data were obtained, and immunolabelling for chromogranin A, pancytokeratin, cytokeratin 14, Ki67 and p63 was performed. Solid carcinomas were classified into six subgroups: malignant adenomyoepithelioma (68/135), carcinoma with solid pattern (22/135), malignant myoepithelioma (16/135), basaloid carcinoma (14/135), neuroendocrine carcinoma (10/135) and solid papillary carcinoma (5/135). Shorter survival time was associated with the presence of lymphatic invasion (P = 0.009) in the initial clinical staging (I-III). When considering all clinical stages (I-V), vascular invasion (P <0.001) and the presence of regional metastasis (P = 0.004) were important prognostic factors. Basaloid carcinoma and solid papillary carcinoma did not reach the median survival time for early-stage cases, and malignant myoepithelioma had the highest median survival in advanced stages. Carcinoma with a solid pattern was associated with a higher number of regional metastases. Distinguishing the various histological and immunophenotypic subtypes that exhibit a solid arrangement, using histological and immunohistochemical criteria, is essential for understanding the behaviour of these neoplasms and for the selection of more appropriate and specific therapies.

Canine Mammary Carcinoma With Vacuolated Cytoplasm: Glycogen-Rich Carcinoma, a Histological Type Distinct From Lipid-Rich Carcinoma.

Lipid-rich carcinoma is a rare histotype of canine mammary tumors with cytoplasmic vacuolation. In humans, glycogen-rich carcinoma, secretory carcinoma, and myoepithelial neoplasms are included in the differential diagnosis for lipid-rich carcinoma. The aim of the study was to investigate the existence of histotypes other than lipid-rich in canine mammary carcinomas with vacuolated cytoplasm using a diagnostic algorithm based on histopathology, histochemistry, immunohistochemistry, and ultrastructure and to evaluate the molecular phenotype of these neoplasms. Ten mammary carcinomas were collected, histologically reviewed, and subjected to histochemistry (PAS, PAS with diastase, Alcian blue, Sudan III [1 case], and Congo red [1 case]); immunohistochemistry for CK19, CK5/6, CK14, p63, calponin, vimentin, ER, PR, and HER2; and transmission electron microscopy (TEM). Cytokeratin immunolabeling demonstrated the epithelial origin of all tumors. Sudan III and TEM confirmed the diagnosis of lipid-rich carcinoma in 8 tumors (one amyloid-producing). One tumor was reclassified as a glycogen-rich carcinoma based on PAS reactivity that was diastase-labile, and a second tumor was reclassified as a carcinoma-and-malignant myoepithelioma based on the differentiation markers. Lipid-rich carcinomas were basal-like (5/8), null-type (2/8), and luminal A phenotype (1/8). The glycogen-rich carcinoma was basal-like, while the carcinoma-and-malignant myoepithelioma was luminal A. Vacuolated morphology of neoplastic cells in canine mammary carcinoma can indicate either a neoplasm of luminal epithelial origin with cytoplasmic lipid or glycogen, or vacuolated neoplastic suprabasal myoepithelial cells. Glycogen-rich carcinoma is a novel histological type that should be considered in the differential diagnosis for canine mammary carcinomas with vacuolated cytoplasm.

Malignant Myoepithelioma of the Parotid Gland in a Rat.

Myoepitheliomas of the salivary glands have been described in laboratory mice, but not in rats. A 20-week-old Wistar (Han) female rat developed a white to grey firm mass at the left side of the neck. Histologically, the mass was unencapsulated and infiltrated the adjacent tissue. The tumour parenchyma was cell rich without acinar or tubular architecture. The tumour showed a palisading basal cell pattern adjacent to blood vessels. There were areas of necrosis filled with cellular debris. The tumour cells showed strong immunohistochemical labelling for pan-cytokeratin types I and II (AE1/AE3), pan-cytokeratin (cytokeratins 1, 5, 6 and 8), cytokeratin 5, cytokeratin 14, vimentin and podoplanin, and only very slight positivity for cytokeratin 8 in small areas. There was no expression of smooth muscle actin. Based on the histological appearance and the immunohistochemistry, the tumour was diagnosed as a malignant myoepithelioma of the parotid gland originating from the parotid duct.

Biphasic Feline Mammary Carcinomas Including Carcinoma and Malignant Myoepithelioma.

Feline mammary tumors are usually malignant and aggressive carcinomas. Most cases are simple monophasic carcinomas (1 epithelial population), and additional phenotyping is usually not needed. In this study, we describe 10 malignant mammary tumors from 9 female cats that had unusual histomorphology: they appeared biphasic, with 2 distinct cell populations. Initially, they were morphologically diagnosed as either carcinosarcoma (1/10) or malignant pleomorphic tumor (9/10) of the mammary gland, as the latter did not match any previously described histological subtype. Immunohistochemistry (IHC) was performed for pancytokeratin, cytokeratins 8 and 18, cytokeratin 14, cytokeratins 5 and 6, vimentin, p63, calponin, alpha-smooth muscle actin, Ki-67, ERBB2, estrogen receptor alpha, and progesterone receptor. In 7 of 10 cases, the biphasic nature was confirmed and, on the basis of the IHC results, they were classified as carcinoma and malignant myoepithelioma (4/10), ductal carcinoma (1/10), and carcinosarcoma (2/10). The other 3 of 10 cases were monophasic based on IHC. In the cases of carcinoma and malignant myoepithelioma, the malignant myoepithelial cells were 100% positive for vimentin (4/4) and variably positive for p63, calponin, and cytokeratins (4/4). These findings show that, although rare, biphasic mammary carcinomas do occur in cats. In dogs and humans, tumors composed of malignant epithelial and myoepithelial cells have a less aggressive behavior than certain simple carcinomas, and therefore, their identification might also be clinically significant in the cat.

Hepatic Myoepithelial Carcinoma in a Dog: Immunohistochemical Comparison With Other Canine Hepatic Carcinomas.

An 11-year-old female miniature Dachshund dog presented with a solid, soft, gray mass on the hepatic lateral left lobe. Histologically, the mass consisted of neoplastic proliferation of cells with round nuclei and eosinophilic and vacuolated cytoplasm arranged in alveolar, trabecular, and solid patterns. Immunohistochemically, the neoplastic cells were positive for pancytokeratin (CK AE1/AE3), CK5, CK14, vimentin, Sox9, and myoepithelial markers (α-smooth muscle actin, p63, and calponin). The morphological and immunohistochemical findings indicated a diagnosis of myoepithelial carcinoma. We conducted immunohistochemical studies on other representative canine hepatic tumors. Although the myoepithelial phenotype was not observed in the hepatocellular carcinoma, some tumor cells in cholangiocarcinoma showed immunohistochemical features of myoepithelium, suggesting that some neoplastic cells in cholangiocarcinoma may have the potential to differentiate into myoepithelial cells. To our knowledge, this is the first report in veterinary medicine of a hepatic carcinoma with a myoepithelial phenotype.

Canine Spindle Cell Mammary Tumor: A Retrospective Study of 67 Cases.

Canine spindle cell mammary tumor (CSCMT) is an infrequent canine mammary tumor (CMT) composed of spindle or fusiform cells, which represents a challenge for pathologists and clinicians. Mammary tumors submitted for histopathology from 1998 to 2013 and compatible with CSCMTs were retrospectively selected. The tumors were diagnosed based on the hematoxylin and eosin (HE)-stained section; malignant tumors were graded using a canine soft tissue sarcoma grading scheme and a canine mammary tumor grading scheme, and they were further assigned a diagnosis based on immunohistochemistry (IHC) for pancytokeratin, cytokeratin 14, p63, calponin, vimentin, Ki-67, CD31, desmin, myosin, smooth muscle actin, glial fibrillary acidic protein, and S-100. The origin of the tumors was assessed as mammary, skin, or unknown. The prevalence of CSCMT was 1% of all CMTs. CSCMTs included 3 benign tumors (1 angioma and 2 benign myoepitheliomas) and 67 malignant tumors that after IHC were diagnosed as malignant myoepithelioma (64%), carcinoma and malignant myoepithelioma (19%), hemangiosarcoma (8%), undifferentiated sarcoma (5%), peripheral nerve sheath tumor (3%), and fibrosarcoma (2%). The diagnosis based on the HE-stained section differed from the diagnosis after IHC in 75% of the malignant cases. The majority of malignant CSCMTs were solitary (57%) large tumors (6.42 ± 3.92 cm) with low metastatic potential and high survival rate (8% tumor-related mortality). Higher sarcoma grade was associated with older age (P = .034) and greater tumor size (P = .037). Malignant CSCMTs need to be evaluated by IHC to ensure the histotype and the relatively benign clinical behavior, despite their large size.

Epithelial-Myoepithelial Carcinoma in a Canine Salivary Gland.

A 7-year-old male cavalier King Charles spaniel was presented with a cervical subcutaneous mass. The mass had a multilobular growth pattern and each individual lobule contained ductal epithelial cells and myoepithelial cells surrounding the ductal cells. Immunohistochemically, the ductal epithelial cells were positive for cytokeratin (CK) 7 and CAM5.2 and the myoepithelial cells were positive for α-smooth muscle actin and p63. Both types of cells were positive for CK14, a myoepithelial cell marker. Ultrastructurally, the ductal epithelial cells were attached by desmosomes and contained abundant intracytoplasmic tonofilaments. Some ductal epithelial cells contained myofilaments characteristic of myoepithelial cells. Based on these findings, a diagnosis of epithelial-myoepithelial carcinoma was made. It is presumed that the tumour originated from an intercalated duct in a parotid salivary gland.

Salivary Gland Epithelial-Myoepithelial Carcinoma with High-Grade Transformation in a Dog.

An 8-year-old male neutered standard dachshund was presented with a slowly growing mass in the left submandibular salivary gland. Histopathological examination revealed a tumour that was composed of bilayered duct-like structures with an inner layer of ductal cells and an outer layer of clear cells. Both inner and outer cells in the greater part of the tumour exhibited low to moderate atypia and low mitotic activity. However, a focal area towards the periphery showed enhanced cellular atypia and mitotic activity in tumour cells. Immunohistochemically, the outer layer of clear cells expressed myoepithelial markers, while the inner layer cells were positive for a luminal epithelial marker. No local recurrence or lymph node or distant metastasis was observed 18 months following surgery. Based on the morphology and immunohistochemical findings, a final diagnosis of epithelial-myoepithelial carcinoma with high-grade transformation was made.

Histopathological and immunohistochemical features of atypical epithelial tumours of the gland of the third eyelid in seven dogs.

This report documents the histopathological and immunohistochemical features of atypical epithelial tumours of the gland of the third eyelid (GTE) in seven dogs. Cases 1 and 2 were diagnosed as myoepithelioma, comprising of compressive proliferations of interlacing bundles of neoplastic spindle cells expressing cytokeratin 14, p63, calponin and α-smooth muscle actin. Cases 3, 4 and 5 were diagnosed as complex carcinomas comprising of atypical glandular cells expressing cytokeratin 8/18, together with spindle-shaped or round neoplastic cells expressing cytokeratin 14, p63, calponin and α-smooth muscle actin. Cases 6 and 7 were diagnosed as basal cell adenocarcinomas (BCACs) comprising of a mixed proliferation of glandular and basal-type cells expressing cytokeratin 14 and p63. Therefore, in addition to glandular components, these tumours may include neoplastic cells with a myoepithelial or basal cell phenotype. Hence, there is diversity in the features of epithelial neoplasia of the GTE in dogs, similar to tumours in human salivary and lacrimal glands.

Myoepithelioma of the gland of the third eyelid in a dog.

A 12-year-old female miniature dachshund was presented with a tan-white, firm mass (4 × 3 × 2 cm) occupying the left medial canthus. The mass compressed and displaced the left eye dorsally, and it was surgically removed. Microscopically, the mass was composed of interlacing bundles of spindle cells with clear cytoplasm and a small number of atypical glandular epithelial cells. Immunohistochemically, the spindle cells expressed p63, α-smooth muscle actin and calponin, and were negative for cytokeratin AE1/AE3. The glandular epithelial cells expressed cytokeratin AE1/AE3. Based on these findings, this case was diagnosed as a myoepithelioma of the gland of the third eyelid.

Differences in indicators of malignancy between luminal epithelial cell type and myoepithelial cell type of simple solid carcinoma in the canine mammary gland.

Routinely diagnosed simple solid carcinoma (SSC) of the canine mammary gland comprises a heterogeneous group of tumors. Seventy-two cases that had been diagnosed as SSC based on hematoxylin and eosin-stained tissue sections were reclassified immunohistochemically on the basis of myoepithelial markers p63 and α-smooth muscle actin, as well as a luminal epithelial marker cytokeratin 8. Only 23 cases (32%) were true SSC, composed only of luminal epithelial cells, whereas 11 cases (15%) were malignant myoepithelioma (MM), composed predominantly of myoepithelial cells, and 38 cases (53%) were biphasic carcinoma (BC), characterized by biphasic proliferation of luminal epithelial and basal/myoepithelial components. As the pathological parameters were compared between the reclassified tumor types, infiltrative potential, vascular/lymphatic invasion, lymph node metastasis, and Ki-67 labeling index were higher in true SSC compared with MM and BC, suggesting that the former may exhibit a poorer prognosis compared with the latter two.

Results of surgical excision and evaluation of factors associated with survival time in dogs with lingual neoplasia: 97 cases (1995-2008).

OBJECTIVE: To describe the clinical characteristics, treatments, outcomes, and factors associated with survival time in a cohort of dogs with lingual neoplasia that underwent surgical excision. DESIGN: Retrospective case series. Animals-97 client-owned dogs. PROCEDURES: Medical records of dogs with a lingual tumor examined between 1995 and 2008 were reviewed. Records were included if a lingual tumor was confirmed by histologic examination and surgical excision of the mass was attempted. Data were recorded and analyzed to identify prognostic factors. RESULTS: Clinical signs were mostly related to the oral cavity. For 93 dogs, marginal excision, subtotal glossectomy, and near-total glossectomy were performed in 35 (38%), 55 (59%), and 3 (3%), respectively. Surgery-related complications were rare, but 27 (28%) dogs had tumor recurrence. The most common histopathologic diagnoses for the 97 dogs were squamous cell carcinoma (31 [32%]) and malignant melanoma (29 [30%]). Eighteen (19%) dogs developed metastatic disease, and the overall median survival time was 483 days. Median survival time was 216 days for dogs with squamous cell carcinoma and 241 days for dogs with malignant melanoma. Dogs with lingual tumors ≥ 2 cm in diameter at diagnosis had a significantly shorter survival time than did dogs with tumors < 2 cm. CONCLUSIONS AND CLINICAL RELEVANCE: Similar to previous studies, results indicated that lingual tumors are most commonly malignant, and squamous cell carcinoma and malignant melanoma predominate. A thorough physical examination to identify lingual tumors at an early stage and surgical treatment after tumor identification are recommended because tumor size significantly affected survival time.

Isolation, purification, culture and characterisation of myoepithelial cells from normal and neoplastic canine mammary glands using a magnetic-activated cell sorting separation system.

Mammary gland tumours, the most common malignant neoplasm in bitches, often display myoepithelial (ME) cell proliferation. The aim of this study was to isolate, purify, culture and characterise ME cells from normal and neoplastic canine mammary glands. Monodispersed cells from three normal canine mammary glands and five canine mammary tumours were incubated with an anti-Thy1 antibody and isolated by magnetic-activated cell sorting (MACS). Cells isolated from two normal glands (cell lines CmME-N1 and CmME-N2) and four tumours (cell lines CmME-K1 from a complex carcinoma, CmME-K2 from a simple tubulopapillary carcinoma, and CmME-K3 and CmME-K4 from two carcinomas within benign tumours) were cultured in supplemented DMEM/F12 media for 40days. Cell purity was >90%. Tumour-derived ME cell lines exhibited heterogeneous morphology, growth patterns and immunocytochemical expression of cytokeratins, whereas cell lines from normal glands retained their morphology and levels of cytokeratin expression during culture. Cell lines from normal glands and carcinomas within benign tumours grew more slowly than those from simple and complex carcinomas. This methodology has the potential to be used for in vitro analysis of the role of ME cells in the growth and progression of canine mammary tumours.

Complex apocrine carcinoma with dominant myoepithelial proliferation in a dog.

A rare case of complex apocrine carcinoma displaying dominant myoepithelial proliferation developed in the right leg subcutis of a 10-year-old male dog. The major cell population consisted of diffusely proliferating p63-expressing neoplastic cells that were largely myoepithelial in origin co-expressing α-smooth muscle actin. A small portion of the cell population consisted of concomitant basal epithelial cells lacking α-smooth muscle actin expression. The minor population consisted of p63-negative apocrine gland cells that expressed cytokeratin 8. The myoepithelial cell population showed a rather stronger proliferation activity than did the apocrine epithelial population. Thus, this tumor might have been derived from basal epithelial cells characterized by more predominant myoepithelial differentiation than luminal apocrine epithelial differentiation.

Expression of 14-3-3 σ protein in normal and neoplastic canine mammary gland.

14-3-3 σ protein is a negative cell cycle regulator, with both reduced and elevated levels associated with cancer in humans. This study assessed the expression of this protein in canine mammary tissues using immunohistochemistry and Western blotting. 14-3-3 σ was detected in 97% of the mammary tissue samples examined and was found in both myoepithelial (MECs) and epithelial (ECs) cells. Expression levels were elevated and reduced in neoplastic ECs and MECs, respectively (P<0.001). Intense expression of 14-3-3 σ was detected in neoplastic ECs infiltrating blood vessels and lymph nodes and suggests a possible role for this protein in the malignant transformation of mammary neoplasms. Moreover, double immunostaining for 14-3-3 σ and the MEC-specific marker p63, confirmed that 14-3-3 σ is a highly sensitive marker of MECs since all p63-positive cells were also positive for 14-3-3 σ. However, this protein is not exclusive to MECs as ECs also labelled positively.

Increased expression of C5a receptor (CD88) mRNA in canine mammary tumors.

Mammary tumors are among the most common neoplastic conditions in dogs, and there is evidence that inflammation plays a role in the development of some tumor types in dogs. The complement system is a major participant in the inflammatory process and the complement activation component, C5a, is a potent inflammatory peptide. This study investigated the mRNA expression of the major receptor for C5a (C5aR; CD88) in histopathological samples of canine mammary tumors by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) using canine-specific primers for CD88. A total of seven canine mammary tumors (four malignant carcinomas, two benign mixed mammary tumors, and one myoepithelioma) and eight normal mammary glands were analysed. All the tumor samples expressed low levels of CD88 mRNA, while none of the normal mammary tissues showed any detectable expression. These preliminary results suggest that C5a-CD88 interaction may play a contributory role in the inflammatory response associated with mammary tumor development in dogs. Further studies investigating the mechanisms behind complement activation and C5a receptor expression in canine mammary tumors are warranted.

Sebaceous metaplasia in a canine mammary gland non-infiltrative carcinoma with myoepithelial component.

Sebaceous metaplasia in canine mammary tumors is a rare condition with only 1 case documented. The current study describes a case of sebaceous metaplasia in a mammary gland carcinoma of an 8-year-old intact, nulliparous female Poodle dog with a subcutaneous tumor located in the left fifth mammary gland. The lesion measured 0.7 cm × 0.5 cm × 0.6 cm in diameter, was firm, circumscribed, painless, non-haired, and non-ulcerated, and did not adhere to deep tissues. The cut surface was non-lobulated, non-encapsulated, whitish to gray, and opaque. Histological evaluation revealed 3 different populations of cells: the first was composed of columnar to cuboidal malignant epithelial cells arranged in intraductal papillary projections, the second of myoepithelial cells associated with a myxoid stroma, and the third presenting sebaceous metaplasia similar to those previously described in both human and veterinary medicine.

AE1/AE3, vimentin and p63 immunolocalization in canine mammary gland tumours: roles in differentiation between luminal epithelial and myoepithelial lineages.

Mammary tumors are by far the most common tumors in female dogs and effective treatment relies on prompt and accurate diagnostic procedures. Canine mammary tumors may originate from various cell types, such as luminal epithelial, myoepithelial and stromal cells. This study aimed to differentiate luminal epithelial and myoepithelial lineages, using specific markers including AE1/AE3, Vimentin, and p63. Such data can be useful for prognosis. Canine mammary tumors were collected by surgical resection and tissue samples were investigated using the avidin-biotin-immunoperoxidase method with used primary antibodies against AE1/AE3, vimentin, and p63. Luminal epithelial-origin tumors were found to be immunoreactive with AE1/AE3 and vimentin monoclonal antibody, while myoepithelial-origin tumors were positive for p63 and vimentin . In addition, canine mixed tumors showed reactivity with all three antibodies. In summary, AE1/AE3, p63 and vimentin can be used as specific immunohistochemical markers to distinguish lumino-epithelial and myoepithelial lineages of canine mammary tumors.

A mammary gland adenomyoepithelioma in a C57BL/6 mouse.

Mammary gland adenomyoepitheliomas are benign complex mammary gland tumors composed of neoplastic cells of epithelial and myoepithelial origins, described in many species (humans, dogs, cats, rats) and rarely in mice. We report here an adenomyoepithelioma in a C57BL/6 female mouse. Histologically, tubes and cords formed by neoplastic epithelial cells were separated by bundles of neoplastic myoepithelial cells in a clear and partially mucinous matrix. The tumor displayed characteristics of a benign neoplastic proliferation with a compressive growth pattern, and moderate cellular pleomorphism and mitotic index. At immunohistochemistry, the epithelial cells were strongly cytokeratin positive; the myoepithelial cells were weakly cytokeratin positive and strongly smooth muscle actin positive. This is to our knowledge, the first report of a mammary gland adenomyoepithelioma in a C57BL/6 mouse.