Fibroblastic osteosarcoma with epithelioid and squamous differentiation in a dog

It's not always histiocytic sarcoma: Immunocytochemistry to identify two unusual tumors in a Bernese Mountain dog

A 7-year-old female spayed Bernese Mountain dog was presented for evaluation of hematuria. Incidentally, a right stifle sarcoma was diagnosed via cytology, which raised concern for histiocytic sarcoma (given the patient's signalment) versus another joint-associated sarcoma. Histopathology and immunohistochemistry revealed a CD18-negative, non-histiocytic origin cell population. Findings were consistent with a joint-associated grade II soft tissue sarcoma (STS). The patient's hematuria was progressive over 5 months, and urinary bladder transitional cell carcinoma (TCC) was diagnosed via cystoscopy and histopathology. An enlarged right medial iliac lymph node was identified on routine restaging via abdominal ultrasound 3 months later. Cytology of the lymph node revealed a markedly pleomorphic cell population, again raising concern for histiocytic sarcoma (HS). Other differentials included an anaplastic metastatic population from the joint-associated STS or the TCC. Immunocytochemistry revealed a cytokeratin-positive, CD18-, CD204-, and vimentin-negative cell population, consistent with a carcinoma. DNA was extracted from cytology slides to sequence cells for BRAF mutation status. Sequencing revealed a homozygous V596E (transcript ENSCAFT00845055173.1) BRAF mutation, consistent with the known biology of TCC. In neither case was HS truly present in this patient, but immunocytochemistry provided information that helped to optimize the patient's chemotherapy recommendations.

Canine oral primary melanoma cells exhibit shift to mesenchymal phenotype and phagocytic behaviour

Canine oral malignant melanoma (COMM) is a potentially lethal cancer disease. We established primary cell lines from mostly amelanotic primary COMM and metastases and assessed lesions and derived cells for Melan A, PNL2 and CD146 expression. Then, migration and invasion of CD146-enriched vs -depleted COMM cells were analysed. Epithelial-to-mesenchymal transition (EMT) was addressed by Vimentin-staining and MMP2/MMP9 zymography. Phagocytic behaviour was analysed by histopathological examination and phagocytosis assay. While Melan A- and PNL2-staining yielded inconsistent data, 100% of COMM sections and primary cells showed CD146 expression, suggesting that this protein may serve as a prognostic marker. An overall correlation between CD146-expression and migration/invasion was not observed. All primary cell lines consistently expressed Vimentin and secreted biologically active MMP2, indicating that they had undergone EMT. Importantly, COMM sections exhibited cell-in-cell structures, and all primary cell lines exhibited phagocytic activity, supporting the concept that cell cannibalism may have a role in COMM progression.