Acinic cell carcinomas display a variety of growth patterns such as solid, follicular, microcystic, and papillary cystic. Solid and microcystic patterns are the most common and are often seen together. The left half of this image shows acinar cells in a solid pattern which gradually merges with the follicular pattern on the right. In a well-differentiated acinic cell carcinoma, the acinar cells predominate; however, in some tumors, they are in minority. Cellular pleomorphism and anaplasia are usually absent and mitotic activity is low. The background stroma is usually scant and vascularized but may be dense and hyalinized. Many cases have a prominent lymphoid stroma which may lead to the mistaken impression of metastatic tumor within a lymph node.