Biological behaviour and morphological characteristics of a transplantable tumour (MM-KMY) derived from a malignant meningioma in an F344 rat.

A subcutaneously transplantable meningeal tumour (MM-KMY) was derived from a spontaneous malignant meningioma which developed in the cerebellar meninges of a female F344 rat. MM-KMY was subjected to 25 serial passages in syngeneic male and female rats. The transplants grew in 8 weeks into a nodule with an average diameter of 5.7 cm and average weight of 125.2 g. MM-KMY possessed large cysts containing fluid and necrotic tissue. Metastases frequently occurred in the lungs of MM-KMY-bearing rats. Histologically, both the original tumour and MM-KMY consisted of round to fusiform neoplastic cells of varying size, with nuclear pleomorphism. Mitotic figures occurred frequently. MM-KMY cells were positive for vimentin. Ultrastructurally, the cells showed desmosome-like structures, interdigitating processes and cytoplasmic intermediate filaments, suggesting an arachnoid cell origin. Abnormal accumulations of hyaline droplets in renal tubular epithelial cells were frequently observed in MM-KMY-bearing rats, suggesting overload of low molecular proteins in the renal tubules. The droplets gave a faint immunoreaction for lysozyme. The relation between the appearance of renal tubular hyaline droplets and the growth of MM-KMY remains to be determined. MM-KMY may prove useful for studying the biological behaviour and morphogenesis of meningeal tumours.