MORPHOLOGICAL-CHARACTERISTICS OF A TRANSPLANTABLE HISTIOCYTIC SARCOMA(HS-J) IN F344 RATS AND APPEARANCE OF RENAL TUBULAR HYALINE DROPLETS IN HS-J-BEARING RATS

A transplantable tumour (HS-J) was established from a spontaneous hist iocytic sarcoma found in a 24-month-old male F344 rat. Serial transpla ntations (seven generations) were made in syngeneic male and female ra ts by means of intraperitoneal or subcutaneous implants, with a 100% t ake rate. Rats organs. HS-J tumours consisted mainly of round to oval cells with abundant cytoplasm, arranged in a compact sheet. Enzyme- an d immuno-histochemical examination showed that neoplastic cells reacte d with ED1 (rat monocyte/macrophage-specific antibody), lysozyme, alph a 1-antitrypsin and lysosomal enzymes (acid phosphatase and non-specif ic esterase), indicating derivation from cells of the monocyte/macroph age lineage. The majority of neoplastic cells were negative for ED2 (r at tissue macrophage-specific antibody). Abnormal accumulations of hya line droplets in the proximal renal tubular epithelial cells were seen in HS-J-bearing rats. The droplets were faintly immunopositive for ly sozyme, but negative for alpha-2u globulin and albumin. It was conside red that excessive production of the protein by tumour cells might lea d to subsequent overload in renal tubules. HS-J may prove beneficial f or studying the biological behaviour of monocyte/macrophage-derived ru mours in the rat. (C) 1997 W.B. Saunders Company Limited.