A two-year-old, neutered female cross-bred labrador had multiple cutaneous nodules, biopsies of which revealed pathological changes consistent with cutaneous histiocytosis. During a period of one month the dog developed multicentric lymphadenopathy, a retrobulbar mass and masses within the quadriceps and cervical muscles. Fine needle aspiration cytology of the cutaneous nodules and lymph nodes and histological examination of the cutaneous nodules and muscle masses suggested the presence of lymphoblastic lymphoma. A definitive diagnosis of CD8+ T cell lymphoma was achieved by immunophenotyping the tumour cells by flow cytometry.