Disseminated Pneumocystosis in a Toy Poodle.

A 1-year and 7-months-old neutered male toy poodle was presented with persistent respiratory distress, gradual weight loss and melaena. Thoracic radiography showed an unstructured interstitial lung pattern. Histopathological examination of tissues collected at necropsy examination revealed disseminated infection by Pneumocystis carinii. The organisms were detected in the lungs, lymph nodes, liver, heart, kidneys, spleen, gastrointestinal tract and pancreas. In the lungs, the organisms were present in the alveolar space and interstitial tissue, and calcified foci containing P. carinii were observed. The presence of the organism in non-thoracic lymph nodes provided evidence of lymphogenous spread. A definitive diagnosis of disseminated pneumocystosis was achieved through the use of Grocott methenamine silver staining, immunohistochemistry (IHC) and polymerase chain reaction for P. carinii. Depletion of cells expressing immunoglobulin (Ig)A and IgG was confirmed by IHC of lymphoid tissue, suggesting possible underlying immunodeficiency.

Immunohistochemical Profile of Ameloblastic Carcinoma Arising from an Amyloid-Producing Odontogenic Tumour in a Miniature Dachshund.

A 13-year-old female miniature dachshund was presented with a centrally-located sublingual mass in the rostral mandibular region. The focally ulcerated growth completely covered the left (305) and right (405) premolar teeth and partially covered the right canine teeth (404). A punch biopsy sample revealed neoplastic proliferation of odontogenic epithelium arranged in irregular cords with frequent comedo-like necrosis. Following the initial diagnosis of ameloblastic carcinoma, a bilateral rostral hemimandibulectomy was performed. Although the detailed examination of the resected mass was consistent with the initial diagnosis, it also contained birefringent congophilic, amelogenin-labelled amyloid deposits similar to an amyloid-producing odontogenic tumour (APOT) in 30-40% of the mass, in continuity with the ameloblastic carcinoma. All neoplastic cells had diffuse moderate expression of cytokeratin (CK) AE1/AE3 and CK5, diffuse mild expression of CK14 and multifocal moderate expression of CK19. Because the APOT-like growth in the mass was histologically benign, the tumour was diagnosed as an ameloblastic carcinoma arising from an APOT.

Merkel Cell Carcinoma in a Steer.

Merkel cell carcinoma is a rare and aggressive cutaneous neuroendocrine tumour reported only in man, dogs and cats. A 20-month-old Japanese black fattening steer was presented with necrotic protruding skin masses over the left thoracic area and a 20 × 25 cm subcutaneous mass in the left abdominal area. Microscopical evaluation of the masses revealed cords of small to medium-sized round tumour cells with marked anisocytosis and anisokaryosis and clear and vacuolated cytoplasm, which were separated by a delicate fibrovascular stroma and arranged in a trabecular and nested pattern. Necropsy examination revealed multiple solid white nodular masses in the lungs. Immunohistochemistry (IHC) for cytokeratin (CK) 20 and CKAE1/3 revealed focal perinuclear labelling of tumour cells. IHC for the neuroendocrine markers chromogranin A and neuron specific enolase, the neuroepithelial stem cell marker nestin and the hormonal markers adrenocorticotropic hormone and calcitonin revealed diffuse cytoplasmic labelling of all tumour cells. Ultrastructurally, the tumour cells contained few neurosecretory granules and abundant glycogen pools. The tumours were diagnosed as Merkel cell carcinoma with pulmonary metastases and this case represents the first such diagnosis in cattle.

Histological and immunohistochemical evaluation of granulosa cells during different stages of folliculogenesis in bovine ovaries.

Bovine granulosa cells (GC) vary in their morphological aspect during different stages of folliculogenesis. In this study, 10 morphologically normal bovine ovaries were collected to study the structural aspects of different stages of GC using intermediate filament protein antibodies including cytokeratin AE1/AE3 (AE1/AE3), vimentin, nectin-4 and desmin. Hormonal immunolocalization was assessed using the immunomarkers anti-Müllerian hormone (AMH) and inhibin alpha. In addition, tumour markers and proliferation markers using c-erbB-2 oncoprotein and proliferating cell nuclear antigen, respectively, were investigated. The immunolabelling of AE1/AE3 in GC was strongest in the early follicle stage and gradually decreased when reaching the Graafian follicle stage. Its immunolabelling increased again as the stage progressed from stage I to stage III. The immunolabelling of inhibin alpha was inversely proportional to that of AE1/AE3 in the developing ovarian follicles as their immunolabelling is opposite to each other during folliculogenesis. AMH was immunopositive in almost all GC stages in different intensities and percentages, except for some negative staining in the atretic IV follicles. The atretic IV follicle is a unique type of atretic follicle that shows Call-Exner body formation, which was mainly found in older cows in this study. The distinct patterns of immunoreactivity for various types of immunomarkers in the different GC stages will play an important role in diagnostic assistance of various follicle conditions, including cystic ovaries and GC tumours.