Polymorphous low-grade adenocarcinoma of the upper lip: 11 cases of an uncommon diagnosis.

OBJECTIVE The aim of this case study was to describe an international case series of polymorphous low-grade adenocarcinoma (PLGA) affecting the upper lip. MATERIAL AND METHODS Over a 30-year-period, the files of five pathology services were reviewed for PLGA affecting the upper lip. Hematoxylin and eosin-stained slides were reviewed by three oral and maxillofacial pathologists, and microscopic features were described. Clinical data were retrieved from patients' medical records. RESULTS The review identified 11 cases of upper lip PLGAs, with a complete set of clinical data available for 5 cases. There was a male predominance (1.2:1), and the mean age was 58.7 years. Most cases presented as small asymptomatic swellings that resembled benign tumors. All patients underwent surgery, and no recurrences or metastases were reported in the 8 cases from which follow-up data were available. Microscopically, the typical polymorphic architectural arrangement of PLGA was seen in all cases, with lobular, trabecular, papillary, and cribriform patterns identified. Perineural invasion, normal gland entrapment, Indian filing, and concentric growth were frequently identified. CONCLUSION PLGA must be included in the list of differential diagnoses of tumors affecting the upper lip because of its similar clinical presentation to benign entities. The follow-up data available from 8 of 11 cases suggest that these tumors follow a low-grade clinical course, similar to the majority of palatal cases of PLGA.