Ultrastructural pathology of cutaneous tumours of northern pike, Esox lucius L.

Abstract

An epidemic of cutaneous tumours occurs in northern pike, Esox lucius L., from the Aland Islands of Finland. Previous studies have shown that the neoplasm is of mesenchymal origin and that it is not of B-lymphocytic lineage; however, a T-lymphocytic origin could not be totally excluded. Here the authors provide morphologic evidence that the tumour could, in fact, be monocyte derived. The close apposition of the tumour cells with a lack of cell-cell junctions is in keeping with the view that it is not of epithehal origin. A striking morphologic characteristic of the tumour cells is the presence of groups of lysosomes and large numbers of cytoplasmic lipid droplets. Therefore, the authors suggest that the tumour cells have features of histiomonocytic cells and that the neoplasm might be a piscine analogue of true histiocytic lymphoma in humans. These studies represent the first description of this type of neoplasm in fish.

Immunohistochemical characterization of malignant lymphoma in northern pike, Esox lucius L., from Estonian Baltic waters

“…All previous studies carried out on both frozen and paraffin wax sections of head kidney and tumour, using anti-AAT and anti-LYS antibodies, have produced negative results (Thompson & Miettinen 1988), Thompson & Miettinen (1988) suggested that the negative findings of LYS in pike may only reflect the time of sampling. On the other hand, LYS may not occur in pike, as established in cod, Gadus morhua L., (Fletcher & White 1973), or it may be present in antigenically different forms as observed in plaice, Pleuronectes platessa L., (Murray & Fletcher 1976) or in lumpsucker, Cyclopterus lumpus L., (Fletcher, White & Baldo 1977).…”