Transplantable murine salivary gland carcinoma (myoepithelioma). I. Biologic behavior and ultrastructural features.

Three salivary gland adenocarcinomas that arose spontaneously in female BALB/c mice, originally being maintained for plasmacytoma (MOPC) investigations, were studied; only one of the original hosts was MOPC-bearing. The initial carcinomas clearly originated from the salivary gland, not the breast, and did not resemble plasma cell lesions. The submandibular gland was the site of origin in each instance. Lesions were identical to those described previously in strains A and C mice as myoepitheliomas, with intracellular fibrils positive by phosphotungstic acid-hematoxylin (PTAH) stain. Each cell line (A, B, and C) of the salivary gland carcinomas was serially transplanted for 28, 29 and 14 generations, respecitvely. The lesion was easily transplanted, achieved almost 100% takes, and uniformly killed the host in 6-12 weeks, with metastasis to the peritoneum and liver. A myeloproliferative reaction characterized by leukemoid changes regularly occurred during the growth of the tumors. Each transplant generation was identical to its original salivary gland precursor by light and electron microscopy. In their growth pattern, the tumors resembled sarcomas with large areas of spindle cells. Ultrastructurally, the neoplastic cells contained the organelles of acinar and possibly ductal cells and exhibited varying degrees of synthetic and secretory activity, characterized by abundant free ribosomes and granular ergastoplasm, with prominent canaliculi containing abundant secretory material. Numerous desmosomes were seen, as well as coarse filaments and fine fibrils in most tumors cells, particularly in cells exhibiting lesser degrees of secretion. The filaments most likely represented the PTAH-positive intracellular fibrils observed by light microscopy. All tumors had numerous cells with resting features.