Polymorphous low-grade adenocarcinoma: an analysis of epidemiological studies and hints for pathologists

Abstract

BackgroundThis study is an analysis of the prevalence of polymorphous low grade adenocarcinoma (PLGA) in epidemiological surveys of salivary tumors published in the English language from 1992 to 2012.MethodsThese surveys included studies from different researchers, countries and continents. The 57 surveys for which it was possible to calculate the percentage of PLGAs among all malignant minor salivary gland tumors (MMSGT) were included in this review.ResultsThe statistical analyses show significant differences in the PLGA percentage by time period, country and continent in the studies included in this review. The percentage of PLGAs among MMSGTs varied among the studies, ranging from 0.0% to 46.8%. PLGA rates have varied over the period studied and have most recently increased. The frequency of reported PLGA cases also varied from 0.0% to 24.8% by the country in which the MMSGT studies were performed. The PLGA percentages also varied significantly by continent, with frequencies ranging from 3.9% in Asia to 20.0% in OceaniaConclusionBased on these results, we concluded that although the accuracy of PLGA diagnoses has improved, they remain a challenge for pathologists. To facilitate PLGA diagnoses, we have therefore made some suggestions for pathologists regarding tumors composed of single-layer strands of cells that form all of the histological patterns present in the tumor, consistency of the cytological appearance and uniformly positive CK7, vimentin and S100 immunohistochemistry, which indicate a single PLGA phenotype.Virtual slideThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1059098656858324

Polymorphous Low Grade Adenocarcinoma has a Consistent p63+/p40− Immunophenotype that Helps Distinguish it from Adenoid Cystic Carcinoma and Cellular Pleomorphic Adenoma

“…Additionally, Woo et al [17] reported that CD43 is more strongly expressed in adenoid cystic carcinoma than PLGA, a finding that has not yet been confirmed by other investigators. Unfortunately, other immunostains, including S100 and bcl-2, have not consistently helped differentiate PLGA from either adenoid cystic carcinoma or pleomorphic adenoma [13,18,39]. p63, an immunohistochemical stain that highlights basal and myoepithelial differentiation, has never routinely been used to distinguish between PLGA, adenoid cystic carcinoma, and pleomorphic adenoma because all three lesions are frequently positive for this marker [23,25,26].…”

Expression of Human Tissue Kallikreins (KLKs) in Polymorphous Low Grade Adenocarcinoma (PLGA)

“…In their 2013 epidemiologic study, de Araujo et al noted a significant increase in the fraction of PLGA cases reported in the literature since 2007, but did suggest this was secondary to improved diagnostic accuracy by pathologists [16]. PLGA is most commonly found in the Caucasian population; however, some publications have reported higher incidences amongst Asian and African populations [11,16,17]. Two retrospective studies out of Northeast and Eastern China documented a lower incidence of PLGA in these regions, than that noted globally [4,18].…”

“…PLGA has a female predilection, with a female-to-male ration of 2.15:1 [11,19]. PLGA is most frequent in the 6 th and 7 th decades; the age of presentation peaks during the 6 th decade [16,20]. Cases in the literature vary from the 2 nd to 10 th decades of life, with the mean age at time of diagnosis being 61.3 years of age [4,11].…”

“…The most common location to develop PLGA is on the palate, particularly at the junction of the hard and soft palate, where many minor salivary glands reside [11,13,16]. PLGA is also regularly found on the lips, as well as the buccal mucosa.…”

“…The average tumour size at the time of presentation is 2.1 cm +/-1.3 cm [11,14,16]. PLGA may be locally invasive, for example, palatal lesions will eventually invade the adjacent maxillary bone and sinuses [19].…”