道下 正貴

A 21-year-old neutered female domestic shorthaired cat was presented with a history of inappetence, vomiting and haematuria. The cat was humanely destroyed at the owner's request and a necropsy examination was performed. A 0.8 x 0.5 x 0.5 cm mass was located in the left lobe of the pancreas. The mass was gelatinous in nature and the external and cut surfaces were pale yellow in colour. Microscopically, the mass was non-capsulated and comprised an accumulation of extracellular stromal mucin containing suspended neoplastic columnar epithelial cells forming tubular structures. Immunohistochemically, these cells diffusely expressed cytokeratin (CK) AE1/AE3, CK7 and carcinoembryonic antigen and were partially positive for CK19 and trypsin, but negative for vimentin. The tumour was diagnosed as a colloid carcinoma. The clinical presentation in this case was caused by chronic renal failure complicated by secondary renal hyperparathyroidism and associated metastatic calcinosis. To the best of our knowledge, this is the first report of colloid carcinoma arising from the pancreas in a cat. (C) 2017 Elsevier Ltd. All rights reserved.

A 13-year-old female Yorkshire terrier was presented with difficulty swallowing because of a lingual mass, which had grown to a size of 0.8 × 0.8 × 0.8 cm in 1 month. Grossly, the mass was located in the lingual frenulum and the cut surface was grey-white in colour. Microscopically, the mass was unencapsulated and composed of lobules of mature adipose tissue and cartilaginous tissue with abundant basophilic myxoid matrix separated by fibrous connective tissue. Immunohistochemically, almost all of these cells were positive for vimentin and S100. Chondroid cells and their adjacent spindle cells were also positive for SOX9. Based on these findings, a diagnosis of chondrolipoma was made. To the best of our knowledge, this is the first report of a chondrolipoma originating as a primary tumour in the lingual frenulum of a dog.

A 5-year-old male miniature dachshund was presented with a dermal nodule on the left forelimb that increased to 5 mm in diameter over a 2-month period. Grossly, the nodule was firm, and both the external and cut surfaces were homogeneously pale pink in colour. Microscopically, the nodule was comprised of mainly plump endothelial cells and inflammatory cells; among the latter, lymphocytes were predominant, with few scattered plasma cells, mast cells and macrophages. Lymphoid follicles with germinal centres were often observed. Mitotic figures were not observed amongst the endothelial cells. Immunohistochemically, the endothelial cells were positive for vimentin, factor VIII-related antigen and CD31, and the surrounding cells were positive for smooth muscle actin. Lymphocytes expressed CD3 or BLA36. These findings led to a diagnosis of cutaneous angiolymphoid hyperplasia. To the best of our knowledge, this is the first report of a cutaneous proliferative disorder comprising an admixture of proliferating vascular endothelial cells and lymphocytic infiltration with follicle formation in a dog. (C) 2017 Elsevier Ltd. All rights reserved.

Mammary tumors that spontaneously occurred in domestic Djungarian hamsters (Phodopus sungorus) were histologically examined. Forty-five mammary tumors included 14 adenomas, 18 adenocarcinomas, 1 lipid-rich carcinoma, 2 adenoacanthomas, 2 malignant adenomyoepitheliomas, 1 benign mixed tumor, and 7 balloon cell carcinosarcomas. The latter 4 types were newly recognized neoplasms in Djungarian hamsters. The relatively high incidence of spontaneous mammary carcinosarcomas in domestic Djungarian hamsters is intriguing. Carcinosarcomas exhibited anomalous histological features made up of a mixture of glandular cells, polygonal cells (including balloon cells), and sarcomatous spindle cells in varying proportions. Transitional features from glandular cells to polygonal cells and subsequently to sarcomatous spindle cells were observed. Using immunohistochemistry, we observed that glandular cells exhibited an epithelial phenotype (cytokeratin(+)/vimentin(-)), spindle cells exhibited a mesenchymal phenotype (cytokeratin(-)/vimentin(+)), and polygonal cells exhibited an intermediate phenotype (cytokeratin(+)/vimentin(+)). Reduction or loss of beta-catenin expression and gain of S100A4 expression were observed in polygonal and spindle cells. The polygonal cell population included a varying number of characteristic cells that were expanded by large intracytoplasmic vacuoles. Electron microscopy revealed that these balloon cells had large cytoplasmic lumens lined by microvilli. These observations suggest that epithelial-mesenchymal transition may account for the pathogenesis of mammary carcinosarcomas in Djungarian hamsters.

Tenascin-C (Tn-C) is an extracellular matrix glycoprotein implicated in the progression of several human cancers. In canine mammary carcinomas, accumulation of Tn-C has been recognized in 3 different areas: regions of proliferating myoepithelial cells in complex carcinoma, basement membrane zone in low-grade simple carcinoma, and reactive stroma in high-grade simple carcinoma. To identify the Tn-C synthesizing cells in these areas, we utilized double-labeling immunohistochemistry, branched DNA in situ hybridization, and in situ hybridization-immunohistochemistry double-labeling techniques. In complex carcinomas, Tn-C was generated by proliferating myoepithelial cells. Tn-C in low-grade simple carcinomas was also derived from myoepithelial cells existing as a basal monolayer. However, stromal Tn-C in high-grade carcinomas was mainly synthesized by fibroblasts/myofibroblasts, similar to human breast cancer. Thus, the origin of Tn-C in canine mammary carcinomas differs between low- and high-grade malignancies. The role of myoepithelial cell-generated Tn-C is not yet understood.

Cystic tumours of the pancreas are heterogeneous lesions with a spectrum of morphology and biological behaviour in people. These are poorly characterized in animals. A multicystic tumour of the pancreas was identified in an 11-year-old, female, mixed breed cat. The tumour was 5.5 cm in diameter and the largest cysts were 1.5 cm in diameter. Microscopically, the cysts were lined by single layered or pseudostratified, flat, cuboidal or columnar epithelial cells that occasionally formed papillary structures with a thin fibrous core. The tumour cells had eosinophilic granules in the apical cytoplasm, similar to zymogen granules, and the nuclei were uniform in size and shape. Mitotic figures were not observed. Immunohistochemically, the tumour cells expressed trypsin, but not cytokeratin 7. A diagnosis of acinar cell cystadenoma of the pancreas was made and this is the first report of this tumour in a cat. (C) 2013 Elsevier Ltd. All rights reserved.

飼育ゴマフアザラシ成雄（31歳）の全身性腫瘤を確認した。各腫瘤は有棘細胞由来の腫瘍細胞が充実胞巣状に増殖し，脈管内塞栓も認められた。免疫組織学化学的に腫瘍細胞はサイトケラチンAE1/AE3，ケラチン5，p63に陽性を示し，ビメンチン，サイトケラチンCAM5.2，カルレチニンに陰性であった。本症例は扁平上皮癌と診断し，肺原発と推察した。本例はゴマフアザラシにおける全身転移を伴う扁平上皮癌の初報告である。

少数の細胞集団（癌幹細胞）が癌階層構造を形成するという癌幹細胞発生説が近年提唱されている。癌幹細胞は、自己複製能、分化能、異種移植による腫瘍形成能を有する細胞と定義される。癌幹細胞は、side population解析、細胞表面マーカーによるフローサイトメトリー解析、sphere assayおよびALDEFLUOR assayのようないろいろな方法で同定できる。癌幹細胞の理解は、癌形成機構の解明および新規治療を開発するために最も重要である。しかしながら、獣医学における癌幹細胞研究はほとんど行われていない。本稿では、犬乳腺腫瘍の癌幹細胞の分子生物学的解析および癌幹細胞を標的とする新規治療の展望について述べる。