Mixed tumors of the salivary glands. Growth pattern and recurrence.

In 112 patients with mixed tumors of the salivary glands, 94 tumors were located in parotid glands, 11 in submandibular salivary glands, and 7 in monor palatal salivary glands. Capsular ingrowth, a characteristic growth pattern, may explain the frequency of multilobulation and capsular defects in these tumors, particularly those of long standing. The capsular thickness, the extent of fibrosis with stromal hyalinization, and the degree of lymphocytic infiltration within and around the capsule, were associated with cellularity of the tumors. Thus, 69% of the hypocellular neoplasms had incomplete capsules, and only 13% showed moderate to substantial lymphocytic infiltration; corresponding figures for hypercellular tumors were 22% and 42%, respectively. Of the recurrent lesions, 61% were hypocellular; 11% of the hypercellular tumors recurred. Incomplete resection, hypocellularity, and incomplete encapsulation were considered to be the major factors in recurrence.