Pleomorphic Adenoma Arising From Frontozygomatic Region: An Ectopic Localization

Abstract

Study Design: Case report.

Objective: Pleomorphic adenoma is pathologically characterized as an epithelial lesion intermixed with mesenchymal elements. It is characterized by being a slow-growing, asymptomatic, usually nodular, firm consistency lesion that can reach large dimensions, especially when it affects the parotid gland. The present study aims to report a case about an atypical presentation of pleomorphic adenoma found in frontozygomatic region.

Methods: The tumor mass was removed through resection, under general anesthesia, by cutaneous approach, preserving aesthetics and noble structures as temporalis muscle, orbicularis oculi muscle and frontal branch of the facial nerve. Intra-operative macroscopic assessment showed an encapsulated tumor. After resection, the surgical specimen was sent to the pathology laboratory for histological analysis confirming the diagnosis of Pleomorphic Adenoma.

Conclusions: After 1 year of follow-up the patient had an excellent evolution, without signs of disease recurrence. It demonstrates that, until now, the surgical approach constituted the resolving therapy, even for a lesion in a rare localization.

Introduction

Pleomorphic adenoma (PA) or Benign Mixed Tumor ranks as the most common benign salivary gland tumor, frequently affecting the major salivary glands but also the palatal or labial minor salivary glands. ¹ The occurrence is mostly situated parotid glands (85%) followed by minor salivary glands (10%) and the submandibular glands (5%). ²

The mean age of PA occurrence was 44.14 years with a definite female predilection (M:F ratio = 13:8). It most commonly occurred in the facial region (42.85%), and surgical approach is the preferred intervention.³

The World Health Organization defines PA as a tumor which is localized and presents pleomorphic or mixed characteristic of epithelial origin, which is interwoven with mucoid tissue, myxoid tissue, and chondroid masses. ³

The signs and symptoms of pleomorphic adenoma typically include the growth of a smooth, painless mass on 1 side of the face that gradually enlarges over time. The treatment is surgical, varying the way of removal of the lesion, if this is performed properly, the prognosis is excellent, however, if the entire tumor has not been removed, recurrence may occur.

According to Willis et al, there are 3 hypotheses to explain this kind of heterotopias: abnormal differentiation of the local tissues (heteroplasia), abnormal persistence and development of vestigial structures and dislocation of portion of a deficient rudiment during mass movement and development. ⁴

This study aims to report a case of ectopic pleomorphic adenoma (PA) localized in frontozygomatic region. Due to its rarity, the natural history and prognosis of atypical pleomorphic adenoma keeps being unclear. Physicians need to recognize this entity and complete surgical excision with strict follow-up regimens.

Case Report

A 42-year-old male, melanoderm, presented with frontozygomatic growth localized in the right side, showing firm consistence, sessile base, smooth surface, and normal color. The lesion gradually enlarged for indeterminate years, without pain. The patient was transferred to Hospital Estadual Alberto Torres (HEAT, São Gonçalo, Brazil) in Maxillofacial Surgery Clinic, after he was only accompanied by another department of pathology for 3 months. (Figure 1)

Figure 1.

Increased volume in the frontozygomatic region - right side.

The patient complaint about the swelling and the unaesthetic position in the face. Before the surgery time the surgeon had the lipoma or myoepithelioma as diagnostic hypotheses.

The tumor mass was removed through resection, under general anesthesia, by cutaneous approach, preserving aesthetics and noble structures. Intra-operative macroscopic assessment showed an encapsulated tumor. The excess tissue has also been removed (Figure 2).

Figure 2.

Trans operative aspect of the lesion in the frontozygomatic region.

After resection, the surgical specimen (Figure 3) was sent to the pathology laboratory for histological analysis confirming the diagnosis of Pleomorphic Adenoma (Figures 4-5).

Figure 3.

Macroscopy of the surgical specimen. Tumor measuring 5 cm in greatest diameter and lobulated surface.

Figure 4.

(a) Fibrous Capsule (×4 magnification); (b) Histological aspect of pleomorphic adenoma showing myoepithelial cells in myxoid stroma. (×20 magnification); (c) Glandular epithelium and formation of ductal structures. (×10 magnification); (d) Areas of chondroid material. (×4 magnification).

Figure 5.

Biopsy conclusion.

No records of similar cases were found in the literature, limiting the evolutionary description of other authors. The incision was close to the implantation of the hair, which resulted in a less apparent final scar. The patient evolved well after the surgical treatment, with no complications (Figure 6).

Figure 6.

(a) Scarring appearance in the immediate postoperative period. (b) Scar appearance 1-year after excision.

Discussion

Salivary gland tumors constitute an important area in the field of oral and maxillofacial pathology. Although such tumors are uncommon, they are not rare. Regardless of the site of origin, pleomorphic adenoma typically presents as an enlarged firm, painless, slow-growing volume. ⁴

So, an ectopic appearance can cause a diagnostic dilemma for surgeons and pathological confirmation is crucial. PA is a benign tumor that mainly occurs in the salivary gland but as in this case, given the localization in the facial region a histopathological work-up is crucial to exclude other differential diagnosis. ⁵

In our case, the appearance and the physical examination of the lesion showed a nodular mass, located in a soft tissue region of the right frontozygomatic region, measuring 5 cm in its greatest extent, sessile, well delimited, and asymptomatic to palpation. The skin over the lesion was normal, normochromic, and no cervical lymphadenopathy associated.

The main limitation of the case was the absence of computed tomography, since the gantry system was unavailable, and the patient was accompanied only by pathologist department for 3 months.

Based on clinical aspects, our diagnostic hypothesis was lipoma and myoepithelioma. The current treatment of choice for the lesion was complete surgical excision.

The removed specimen was sent for histopathological examination, which revealed diagnosis compatible with pleomorphic adenoma. Although the possibility of recurrence and/or progression with proper surgical removal, the prognosis is excellent, with a cure rate of over 95%. The risk of recurrence appears to be low for gland tumors minor salivation. Conservative enucleation of tumors of the parotid gland results in recurrence, making the management of these cases difficult due to dissemination in the tumor bed primary. ⁶

This case highlights the need for treatment planning based on a comprehensive evaluation of all diagnostic modalities available including but not limited to imaging exam, physical examination, sign, and symptoms.

Conclusion

After 1 year of follow-up the patient had an excellent aesthetic and functional result, without signs of disease recurrence. It demonstrates that, until now, the surgical approach constituted the resolving therapy, even for a lesion in a rare localization.