Small cellular clusters proliferate in a hypocellular background.
Predominant tubular growth is seen here, showing distinct tubular lumens. These tumors are composed of a single cell type, in contrast to others such as adenoid cystic which contain a dual cell population (ductal and myoepithelial)
Tubules alternates with cystic spaces lined by tumor cells
Radially arranged eosinophilic crystals may be found in PGLA, but are usually found in pleomorphic adenoma.
This area shows higher celluarity, with more extensive solid growth with some trabecular pattern as well .
non-encapsulated tumor, with streaming rows of tumor cells intermingling with normal salivary tissue
PGLA is not infrequently found percolating irregularly into adjacent soft tissues.
Intraneural growth, with concentric growth of tumor cells around the nerve, is also a typical feature.
The chromatin is somewhat distinctive in this tumor The nuclei have an ovoid shape in this area, with finely dispersed chromatin and either inconspicuous or small, single nucleoli. Although mitoses are usually rare, they may be more frequent in recurrent tumors. Note that a mitotic figure is found in this field in this recurrent palatal example.
Polymorphous Low Grade Adenocarcinoma(PLGA) is the second most common intraoral malignant salivary gland tumor (after adenoid cystic carcinoma), and accounts for about one quarter of all intra-oral carcinomas of salivary gland origin.1 The female to male ratio is about 2:1, and the tumor most commonly affects those in the 5th to 6th decades of life.
Approximately 60% of tumors arise in the palate. Other intraoral locations affected include the buccal mucosa, retromolar region, upper lip, and the base of the tongue. Uncommonly the lesions are found in the major salivary and lacrimal glands, nasopharynx and nasal cavity.
These tumors usually present as a painless mass in the palate, being present from weeks to as much as 40 years. Bleeding, telangiectasia, or ulceration of the overlying mucosa may be found occasionally.
Treatment consists of complete surgical excision. Neck dissection should be added for those patients with cervical adenopathy.
The survival rate is excellent. A review of series with large numbers of cases and with long-term follow-up yields a local recurrence rate between 9% and 17% and a regional metastases rate from 9-15%. Tumor related mortality is unusual.
1 Waldron CA, el Mofty SK, Gnepp DR. Tumors of the intraoral minor salivary glands: a demographic and histologic study of 426 cases. Oral Surg Oral Med Oral Pathol 66: 323-333.