Putative neoplastic disorders in mussels ( Mytilus edulis) from Southern Vancouver Island waters, British Columbia

Histologic examination of wild populations of Mytilus edulis in Saanich Inlet, British Columbia, Canada, revealed the presence of a highly invasive neoplasm. Two types of neoplasms were recognized; most were of hematopoietic origin, except in one mussel which had a presumptive gonadal neoplasm. Both types were apparently malignant neoplasms, based on their anaplastic appearance, invasiveness, mitotic activity, and associated tissue necrosis. This condition was observed from what is believed to be the earliest stage of the disease to the terminal stage, in which the connective tissue was almost completely replaced.