P-Glycoprotein and Breast Cancer Resistance Protein in Canine Inflammatory and Noninflammatory Grade III Mammary Carcinomas

P-glycoprotein (P-gp/ABCB1) and breast cancer resistance protein (BCRP/ABCG2) expression are frequently related to multidrug resistance (MDR) in neoplastic cells. Canine inflammatory and grade III noninflammatory mammary carcinomas (IMC and non-IMC) are aggressive tumors that could benefit from chemotherapy. This study describes the immunohistochemical detection of P-gp and BCRP in 20 IMCs and 18 non-IMCs from dogs that had not received chemotherapy. Our aim was to determine if P-gp and BCRP expression was related to the \u201cinflammatory\u201d phenotype, to establish a basis for future studies analyzing the response to chemotherapy in dogs with highly malignant mammary cancer. Immunolabeling was primarily membranous for P-gp with a more intense labeling in emboli, and immunolabeling was membranous and cytoplasmic for BCRP. P-gp was expressed in 17 of 20 (85%) IMCs compared to 7 of 18 (39%) non-IMCs (P = 0.006). BCRP was expressed within emboli in 15 of 19 (79%) emboli in IMC, 12 of 15 (80%) primary IMCs, and 12 of 18 (67%) non-IMCs, without statistically significant differences (P >.05). All IMCs and 67% of non-IMCs expressed at least 1 of the 2 transporters, and 63% (12/19) of IMCs and 39% (7/18) of non-IMCs expressed both P-gp and BCRP. P-gp and BCRP evaluation might help select patients for chemotherapy. P-gp, expressed in a significantly higher percentage of IMCs vs non-IMCs, might play a specific role in the chemoresistance of IMC

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

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)\u2013stained 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 \ub1 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

Canine spindle cell mammary tumours : diagnosis, grading and clinical behaviour

Introduction: Canine spindle cell mammary tumours (CSCMTs) represent 0.64% of all mammary tumours and their characteristics and clinical behaviour are mostly unknown. The aims of this study were to characterize microscopical features, clinical aspects and bio- logical behaviour in a series of CSCMTs. Materials and Methods: A total of 70 CSCMTs with demonstrated mammary origin were included in the study. Histology and immunohis- tochemical expression (in 58 cases) of CKAE1/AE3, CK14, vimentin, calponin, p63 and CD31 were evaluated. CSCMTs were graded as sar- comas (s-grade) and as mammary tumours (m-grade) when possible. Results: Dogs with CSCMTs were of different breeds, generally entire (25% neutered) and with a mean age of 10.7 years. CSCMTs were large in size (mean 6.8 cm, 53.1% T3) with infrequent lymph node (6.9%) and distant (3.1%) metastases at diagnosis. Lymph node metas- tases were associated with a high mitotic index (P 5 0.07) and m-grade III (P 5 0.011). After immunohistochemistry (IHC), the most com- mon diagnoses were malignant myoepithelioma (MM) (59.3%), carci- noma and MM (16.9%), haemangiosarcoma (8.5%) and PWT/PNST (6.8%). MMs, best marked by calponin, were frequently solitary tu- mours (P 5 0.049). CSCMTs had a low recurrence/metastatic rate (27.6%). Distant metastases were associated with extensive necrosis (O50%) in the primary tumour (P 5 0.025) and the histological type of CSCMT (P 5 0.04). Cause of death was generally the develop- ment of other non-CSCMT malignant mammary tumours (P 5 0.023). Conclusions: CSCMTs generally demonstrated low recurrent/met- astatic potential. Extension of necrosis and identification of the spe- cific histological type with the aid of IHC may assist in the identification of CSCMTs with malignant behaviour