Case report of viral-associated chondroma (chondrogenic neoplasia) in largescale mullet, Planiliza macrolepis, from Pondicherry, Southeast Coast of India.

Neoplasia in wild fish populations is increasingly recognized as an important indicator of environmental stress and ecosystem health. The present study reports the first documented case of chondroma in the largescale mullet Planiliza macrolepis from the southeast coast of India. An adult female exhibiting a conspicuous external tumorous growth near the caudal peduncle was collected from the Pondicherry fish landing centre during a routine survey. Gross examination revealed a firm, irregular, pinkish-white mass measuring approximately 3.0 × 3.1 × 3.2 cm. Histopathological analysis demonstrated a well-circumscribed cartilaginous neoplasm composed of abundant chondroid matrix containing well-differentiated chondrocyte-like cells within distinct lacunae, with mild focal hypercellularity, mild nuclear pleomorphism, occasional binucleation, and no mitotic figures. Histochemical staining with Alcian Blue (pH 2.5) and Toluidine Blue confirmed the cartilaginous nature of the extracellular matrix. Ultrastructural examination using transmission electron microscopy revealed the presence of virus-like particles within the neoplastic cells, suggesting a possible viral association. Chondroma is rare in teleost fishes, and this finding expands the known host range of chondrogenic tumours in aquatic vertebrates. The present case highlights the need for continued surveillance of neoplastic diseases in marine fishes and underscores the potential role of infectious agents and environmental stressors in tumorigenesis within coastal ecosystems.