Cytopathological Comparison of Well and Poorly Differentiated Canine Soft Tissue Sarcomas (Fibrosarcomas): Diagnostic Challenges in a Resource-Limited Setting

Abstract

Canine fibrosarcoma is a malignant mesenchymal neoplasm arising from fibroblasts, with behavior ranging from slowly growing, well-differentiated masses to highly aggressive, poorly differentiated lesions. In resource-limited veterinary practices, diagnosis often hinges on fine‑needle aspiration cytology (FNAC) and basic radiography, while histopathology and immunohistochemistry remain inaccessible luxuries. We present two cases: a 7-year-old bitch with an 8 cm ulcerated tail‑base mass (2 cm ulcer opening) and a 1.2 cm × 1.0 cm adjacent nodule, and a 4-year-old Boerboel with a 6 cm × 5 cm × 4 cm mediastinal mass exhibiting coagulative necrosis and local invasion. FNAC of the tail lesion yielded moderately cellular smears with spindle-shaped cells, mild anisokaryosis, and occasional mitoses in an inflammatory background, prompting a presumptive fibrosarcoma diagnosis. In contrast, aspirates from the mediastinal mass were hypocellular, showing pleomorphic spindle cells with elevated mitotic figures, leading initially to misclassification as a benign process. Subsequent histopathology confirmed a high-grade fibrosarcoma, highlighting FNAC's limitations when cellular yield is poor. Definitive diagnosis via biopsy and histopathology remains the gold standard for assessing tumor architecture and mitotic index, but is frequently constrained by cost, logistics, and lack of specialized laboratories. To improve diagnostic accuracy and patient outcomes, we advocate for optimized sampling techniques—targeting firm tumor regions and avoiding necrotic centers—developing subsidized regional pathology support, integrating basic imaging modalities, and emphasizing humane pain management consistent with animal welfare principles.