Morphology and immunophenotype of canine cutaneous histiocytic tumours with particular emphasis on diagnostic application.

This study evaluated the morphology and immunohistochemistry of 85 canine cutaneous histiocytic tumours. The tumours were classified morphologically as either canine cutaneous histiocytomas (71 tumours) or canine cutaneous histiocytic sarcomas (14 tumours). The immunohistochemical analysis was conducted on paraffin sections using an antibody panel (against MHCII, CD18, CD79αcy, CD3 and E-cadherin). Histochemical staining with toluidine blue and Gomori silver impregnation was also performed. A follow-up was conducted via surveys. The histiocytic origin of the tumour cells was confirmed in 65 of the canine cutaneous histiocytomas and in 4 of the canine cutaneous histiocytic sarcomas. The tumours that had been misdiagnosed as canine cutaneous histiocytomas included plasmacytomas, epitheliotropic T-cell lymphomas and undetermined entities. The tumours misdiagnosed as canine cutaneous histiocytic sarcomas included plasmacytomas and non-epitheliotropic T-cell lymphomas, but the majority of them remained undetermined. The canine cutaneous histiocytomas showed MHCII, CD18 and E-cadherin expression, but in several of the tumours, the expression of CD18 or E-cadherin was confirmed in only a small percentage of the tumour cells. The regressing canine cutaneous histiocytomas showed increased T- and B-lymphocyte infiltration, a decreased mitotic index, transport of the MHCII molecules from the cytoplasm to the cell membrane and loss of E-cadherin expression in the tumour cells. The canine cutaneous histiocytic sarcomas showed both high morphological diversity and expression of MHCII and CD18. Two of the evaluated histiocytic sarcomas also showed expression of E-cadherin. In conclusion, immunohistochemistry, including analysis of MHCII, CD18 and the lymphocytic markers CD3 and CD79, should be performed for the diagnosis of canine cutaneous histiocytic tumours. The expression of E-cadherin in canine cutaneous histiocytic sarcomas suggests an origin of the tumour cells among Langerhans cells.

Extragonadal teratoma in a domestic turkey (Meleagris gallopavo domestica).

This is the first report of a primary, spontaneous and, most probably, congenital teratoma in a domestic turkey, localized in front of the left eyeball. The unique localization allowed surgical excision of the tumour. The histopathological examination revealed that the tumour included structures derived from all three germ cell layers: ectoderm, mesoderm and endoderm (e.g. cartilaginous, osseous, haematopoietic, fibrous, nervous, glandular, squamous epithelial and smooth muscle tissues). The presence of epithelial cells as well as smooth muscle cells was confirmed using anti-cytokeratin and anti-desmin antibodies, respectively. The proliferative activity of the tumour cells was confirmed using proliferating cell nuclear antigen immunostaining. The other cases of teratoma in wild and domestic birds are reviewed briefly.