Lymphangiosarcoma with bone formation of the auricle in a dog.

A 12-year-old mixed-breed neutered female dog was referred with cutaneous tumors at the left auricle. Histologically, the cutaneous tumor located in the dermis comprised numerous clefts and cavernous channels lined by neoplastic endothelial cells with no erythrocytes. Bone tissue without direct contact with neoplastic cells was seen in the well-developed stromal connective tissue. The neoplastic endothelial cells exhibited mild to moderate atypia. Immunohistochemically, neoplastic cells were positive for vimentin and negative for cytokeratin and factor VIII-related antigen. Basement membrane around the neoplastic lumens was positive for laminin in a linear or granular pattern. Ultrastructural examination revealed discontinuous basement membrane beneath the tumor cells. Histopathological features of this case were consistent with lymphangiosarcoma, and stromal ossification was characteristic.

Mammary adenoma with sebaceous differentiation in a dog.

The current report describes a complex canine mammary adenoma with a rare histological feature characterized by sebaceous differentiation of tumor cells. A 13-year-old, mixed-breed, intact female dog had mammary tumors on the right mammary chain. Histologically, one of the masses was composed of bilayered ductal structures with luminal epithelial cells together with basaloid or myoepithelial cell components. Within the tumor, there were a number of lobules and nests of large foamy cells associated with basaloid reserve-like cells similar to sebaceous gland. Squamous metaplasia was also seen within the tumor. Immunohistochemical staining indicated that the tumor cells with sebaceous differentiation were positive for cytokeratin (CK)14 and that the associated basaloid reserve-like cells were positive for p63. In contrast, other luminal epithelial tumor cells were positive for CK18 and CK19, but not for CK14 and p63. The myoepithelial cells were positive for α-smooth muscle actin and p63. The expression of p63 in both sebaceous basaloid reserve-like cells and myoepithelial cells, and their structural continuity within the tumor tissue, suggested a common origin of these 2 components.

Caudal vascular hamartoma accompanied by aberrant arteriovenous structures in a dog.

A 9-year-old, female German Shepherd Dog presented with a firm bulging lesion at the tip of the tail. Histologically, the lesion was characterized by numerous poorly circumscribed clusters of vascular structures resembling capillaries that were separated by normal or mucinous connective tissues. The capillary-like vascular structures were composed of several layers: a single von Willebrand factor-positive endothelial cell layer with round, oval, or flattened hyperchromatic nuclei; and 1 or 2 surrounding spindle-shaped smooth muscle actin-positive pericyte layers. In the deep portion of the lesion, there were large vessels that showed morphological aberrations. These thin-to-thick-walled blood vessels corresponded to arteries and veins of varying diameters and were surrounded by fibrosis. The present case report describes a rare cutaneous vascular hamartoma, accompanied by aberrant arteriovenous structures.

Progression of glomerulonephritis to end-stage kidney disease in a cat with nephrotic syndrome.

A percutaneous renal biopsy was performed on a 3-year-old female Japanese domestic cat with pleural effusion, mild azotemia, hypoalbuminemia, hypercholesterolemia, and proteinuria. Glomerular lesions included mild diffuse hypercellularity and numerous capsular adhesions with segmental sclerosis/hyalinosis of glomerular tufts. Electron microscopy revealed many subendothelial dense deposits with characteristic outer protrusion of glomerular basement membrane. Diffuse and global granular deposits of IgG and C3 were detected along the capillary walls. Tubulo-interstitial changes were mild at the time of biopsy, but progression of the disease was predicted because of the many capsular adhesions of the glomerular tufts. The cat was fed a prescription diet without any other specific or symptomatic therapy after renal biopsy, and died 43 weeks after the biopsy. At necropsy, extensive tubulo-interstitial fibrosis and mononuclear cell infiltration had developed throughout the cortex and outer medulla, and most glomeruli had extensive global sclerosis or obsolescence with less prominent depositions of IgG and C3.

A case of canine cutaneous clear cell adnexal carcinoma with prominent expression of smooth muscle actin.

Cutaneous clear cell adnexal carcinoma was found in the right lip of a 14-year-old male castrated Shih Tzu. Histologically, the tumor mostly consisted of neoplastic cells with clear or vacuolated cytoplasms and contained frequent tubular structures. Neoplastic cells showed coexpression of pan-cytokeratin (CK) and vimentin by double-labeled immunofluorescence staining. In addition, immunohistochemistry revealed that the tumor cells were positive for pan-CK (AE1/AE3, KL1, CAM 5.2), CK-7, CK-8, CK-14, CK-15, CK-18, vimentin and alpha-smooth muscle actin (SMA) with varied intensity and positivity. Among these marker proteins, SMA was positive in 75% of the tumor cells. On the other hand, CK-15, which is a specific marker of follicular stem cells, was expressed in less than 1% of the tumor cells. Based on these findings, the tumor showed diverse differentiation in apocrine sweat glands and the inner and outer root sheaths of hair follicles, indicating the follicular stem cell to be the origin of this tumor.

Auricular chondritis associated with systemic joint and cartilage inflammation in a cat.

An adult, Japanese domestic cat presented with bilateral swelling, distortion, and erythema of ears and deformation of the limbs. Biopsy of the pinnae confirmed auricular chondritis. These lesions and the cat's general condition subsequently deteriorated, and the cat died. At necropsy, chondral changes were present in the pinnae, costae, larynx, trachea, and limbs. Histopathologically, these chondral tissues showed marked deformation with lymphocytic inflammation. The limb joint inflammation was associated with chondral erosion, deformation of subchondral bones with pannus, and thinning of cancellous bones. These lesions were consistent with the diagnostic criteria for human relapsing polychondritis. However, the cat had erosive arthritis, which appeared to be different from human relapsing polychondritis.