Epidermal X-cell pseudotumours on formalin-fixed Pseudopleuronectes obscurus from Hokkaido, Japan. a) A large central dorsal pseudotumour, seen in cross section (b). c) Pseudotumours can extend from the dorsal surface to the ventral surface and remain pigmented. d) Juvenile fish are also infected and ventral pseudotumours can also be unpigmented. Scale bars a, c & d = 3 cm, b = 10 mm.