Abstract
Polymorphous low-grade adenocarcinoma (PLGA) is a rare malignancy most commonly seen in the minor salivary glands. First described in 1983, this entity has been recognized to have an indolent course with rare metastases or deaths. We describe our experience with 17 patients treated at our institution for PLGA from 1984 to 2012. All tumors were located in the oral cavity or soft palate. All patients were treated surgically, with the exception of one patient who declined therapy. No deaths or metastases have been identified in subsequent follow-up. Three patients in this series had undergone prior surgery up to 20 years previously and were treated for recurrences at our institution; no other recurrences have been noted. In summary, PLGA is best treated with wide excision to negative margins with excellent prognosis, but long-term follow-up is recommended given the propensity for late recurrences.
1
Introduction
Polymorphous low-grade adenocarcinoma (PLGA) is a rare, malignant neoplasm of the head and neck, which occurs almost exclusively in minor salivary glands. First recognized as a unique entity in 1983 , the term “polymorphous low-grade adenocarcinoma” was coined one year later by Evans and Batsakis to represent the neoplasm’s histology and clinical course. Reports of the incidence of PLGA vary, but it is generally considered to be the second most common malignancy of minor salivary glands behind adenoid cystic carcinoma, and comprises about 17.3%–26.4% of all minor salivary gland cancers.
PLGA has been a difficult entity to both study and diagnose and it is frequently confused with other salivary tumors . Numerous articles have been published in the pathology and oral and maxillofacial surgery journals, but there have only been a handful of articles in otolaryngology journals, and the majority of these have been single case studies. We present a review of 17 cases of PLGA, which were treated at Wake Forest University Baptist Medical Center since 1984. We also describe two of these cases in greater detail to highlight some of the more distinctive features of PLGA. Lastly, we review some of the existing literature on polymorphous low-grade adenocarcinoma.
1.1
Case study 1
A 49-year-old woman is referred to the otolaryngology clinic for work-up of a palatal tumor. The patient reported the presence of a painless lesion of her roof of mouth. The lesion had been present for several years. Physical examination revealed a firm, 3 cm tumor of the hard palate ( Fig. 1 ). There was no evidence of any locoregional or distant metastases. Biopsies performed by the referring physician demonstrated polymorphous low-grade adenocarcinoma. The patient opted to pursue surgical treatment and received an infrastructure maxillectomy with composite resection of the tumor. Her surgical defect was repaired with a left-sided pedicled temporalis myofascial flap and palatal/pharyngeal advancement flaps.
1.2
Case study 2
An 85-year-old woman presented to the otolaryngology clinic for evaluation of palatal mass. Though the mass was mildly painful, her chief complaint was that her dentures did not fit properly. Review of her records revealed that she had had a similar lesion excised 20 years earlier, which was reported to be an “adenocystic carcinoma.” On examination, the patient had a 3 cm lesion with central ulceration located on the left posterior hard palate. This was noted to extend into the floor of the nasal cavity. Given her advanced age and multiple comorbidities, the patient elected to forgo surgical treatment. Accordingly, the patient was followed clinically. Imaging at her initial presentation and two years later demonstrates the indolent course of PLGA tumors ( Fig. 2 ).
2
Materials & methods
This is a retrospective chart review that involved collecting data from medical records (1984 to present) of patients in the Wake Forest University Baptist Medical Center (WFUBMC) databases. This study was approved by the Institutional Review Board at WFUBMC. The Department of Otolaryngology databases were reviewed for oral and salivary malignancies. Additionally, the Department of Pathology’s database was queried for all cases of “polymorphous low-grade adenocarcinoma” since 1984, the year the terminology was proposed. All medical records identified through these methods were then screened to verify appropriate diagnosis. Only patients with biopsy confirmed PLGA were included in the review. Patients with questionable diagnoses had their pathology slides reviewed by pathologists here at WFUBMC for confirmation prior to their inclusion in the study. Demographics and other pertinent information were then gathered and analyzed. We reviewed the date of birth or age at diagnosis, sex, race, tumor size, tumor location, TNM stage, local and distant metastases, treatment modality, prior treatments, and recurrence.
2
Materials & methods
This is a retrospective chart review that involved collecting data from medical records (1984 to present) of patients in the Wake Forest University Baptist Medical Center (WFUBMC) databases. This study was approved by the Institutional Review Board at WFUBMC. The Department of Otolaryngology databases were reviewed for oral and salivary malignancies. Additionally, the Department of Pathology’s database was queried for all cases of “polymorphous low-grade adenocarcinoma” since 1984, the year the terminology was proposed. All medical records identified through these methods were then screened to verify appropriate diagnosis. Only patients with biopsy confirmed PLGA were included in the review. Patients with questionable diagnoses had their pathology slides reviewed by pathologists here at WFUBMC for confirmation prior to their inclusion in the study. Demographics and other pertinent information were then gathered and analyzed. We reviewed the date of birth or age at diagnosis, sex, race, tumor size, tumor location, TNM stage, local and distant metastases, treatment modality, prior treatments, and recurrence.
3
Results
Our preliminary chart review yielded 24 patients where PLGA was listed as a possible diagnosis. Review of operative specimens confirmed the diagnosis of PLGA in 17 patients, whereas PLGA was not felt to be the most likely diagnosis in 7 patients and they were excluded from the study. Of the remaining patients, there was a slight female predilection, with a male to female ratio of about 1:1.4 ( Table 1 ). The average age of our patients at the time of initial treatment was 62.7 ± 14.2 years. Over two thirds of our patients were Caucasian, the remaining were African–American.
