First Report of Cutaneous Leiomyoma in Plotosus canius (Hamilton, 1822) From the Coastal Waters of Parangipettai, India.

A tumour-bearing Plotosus canius was collected from the Parangipettai fish landing centre on the southeast coast of India. The neoplastic growth measured 3.5 × 2.8 × 1.5 cm and exhibited a dark red coloration interspersed with greyish-white regions. The lesion showed overlying epidermal ulceration and hyperchromatic, hyperaemic features, contrasting with the surrounding tissue that retained the species normal pigmentation. The excised tumour was vascularised and originated from the underlying musculature. Histopathological examination of the ulcerated peripheral region revealed spindle-shaped cells arranged in interlacing fascicles, possessing elongated nuclei, eosinophilic cytoplasm, and lacking significant pleomorphism or mitotic activity. The central region contained spindle-shaped cells arranged in intersecting fascicles and whorled patterns, with uniform elongated nuclei and moderately eosinophilic cytoplasm. The tumour architecture appeared well-organised, exhibiting variable cellular densities and a collagenous stroma with moderate-grade infiltration, but no signs of necrosis. This study presents the first documented case of cutaneous leiomyoma in Plotosus canius from the coastal waters of Parangipettai, India, and provides a detailed histopathological characterisation of the tumour in this species. Therefore, the potential role of environmental pollutants is speculative and warrants further investigation.