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polymorphous low-grade adenocarcinoma

Friday 3 June 2016

PLGA; terminal duct carcinoma, lobular carcinoma, low grade papillary adenocarcinoma


Definition: PLGA is a common tumor of palate with infiltrative growth, multiple architectural growth patterns and cellular uniformity, first described in 1983. It represents 10% of minor salivary gland tumors but only 1% of all malignant salivary gland tumors.

As the name implies, polymorphous low-grade adenocarcinoma (PLGA) is a low-grade neoplasm consisting of a uniform population of tumor cells that are arranged in a variety of architectural patterns (polymorphous). The median age at presentation is in 6th and 7th decades with a female predominance.


It primarily involves minor salivary glands of the oral cavity. Almost two-thirds of cases are located in the palate. It is the 2nd most common type of salivary gland carcinoma in this location after adenoid cystic carcinoma. It may also involve buccal mucosa, upper lip, base of tongue, and retromolar region.

Uncommon locations include major salivary glands, lacrimal gland, nasopharynx, and nasal cavity. PLGA may occur as a malignant component in carcinoma-ex-pleomorphic adenoma.


At low magnification, PLGA appears well-circumscribed but is unencapsulated with a distinctly infiltrative appearance at its periphery. The tumor shown here was located in the palate.

A variety of architectural patterns can be appreciated, including tubular (glandular), trabecular, solid, cribriform, single filing, and papillary. Architectural polymorphism is not unique to polymorphous low-grade adenocarcinoma and can be seen in many different salivary gland tumors.

Polymorphous low-grade adenocarcinoma can show tubular, trabecular, cribriform, and solid growth patterns.

Polymorphous low-grade adenocarcinoma (PLGA) can show cribriform architecture with some foci of trabecular, ductular, and solid patterns.

The tubular areas in PLGA have identifiable lumens which may contain mucin. The tubular structures may be present individually or form complex tubuloglandular structures.

In trabecular foci, the tumor cells are arranged in anastomosing trabeculae some of which may have identifiable lumens.

Papillary areas in a polymorphous low-grade adenocarcinoma usually consist of cystic spaces with intraluminal papillary structures. It may be associated with aggressive behavior with increased risk of regional metastases and local recurrences.


- polymorphous low-grade adenocarcinoma / PLGA

- polymorphous low-grade adenocarcinoma / PLGA : minor salivary, palate; varied architecture; uniform cytology

- PLGA in WebPathology

See also

- salivary gland tumors

  • salivary gland adenocarcinoma