Polymorphous low-grade adenocarcinoma (PLGA) is a malignancy arising predominantly from minor salivary glands. First appearing in the second edition of the WHO Classification of Salivary Tumours in 1991 [1
], it was initially described in 1983 by Batsakis et al. and Freedman et al [2
]. As such, PLGA is a well-defined neoplasm characterized by architectural diversity, cytological uniformity, and indolent clinical behavior. Low-grade papillary adenocarcinoma (LGPA) was first described by Allen et al. in 1974 with a follow up publication by Mills et al. in 1984 [4
]. While it has been described as a histologic variant of PLGA, controversy exists in the literature regarding whether LGPA should be classified as an entity distinct from PLGA based on a more aggressive oncologic potential.
PLGA unified several histologic classifications, including LGPA, terminal ductal carcinoma (TDA), and lobular carcinoma [6
]. Prior to its recognition, it was commonly diagnosed as adenoid cystic carcinoma, while over the last two decades there has been substantial data published on the features of PLGA differentiating the two [8
]. It is the second most common primary minor salivary gland malignancy after mucoepidermoid carcinoma, comprising 9–26.4% of all salivary malignancies [9
]. It commonly arises in the palate (49–77.8%), followed by either the buccal mucosa or upper lip (7.4–13.4%), and can also involve the floor of the mouth, lower lip, alveolar ridge, and tongue [7
]. Additionally, PLGA can arise in the lung [14
], parotid gland [15
], submandibular gland [16
], and maxilla [17
], and two case reports describe it transforming into higher grade neoplasms [18
Despite the controversy regarding LGPA, only five groups have compared the biologic potential of PLGA and LGPA, arriving at conflicting conclusions [6
]. Our purpose in this manuscript is to present a case report of a LGPA and to review the published evidence for classifying LGPA as distinct from PLGA; we believe this is the first case of LGPA with metastases to the femur and scalp.