Pleomorphic adenoma (mixed tumor) of the upper lip: A case report

Abstract

BACKGROUND

Salivary gland tumors are relatively rare. Most minor salivary gland tumors are malignant with benign tumors accounting for 18% of the tumors. Pleomorphic adenoma (PA) is the most common salivary gland tumor. Lip PA is uncommon with 9.8% occurring in the upper lip. We are adding on the knowledge of the rare upper lip PA (benign mixed tumor).

CASE SUMMARY

We report an upper lip PA (benign mixed tumor) in a 28-year-old man. His complaint was a painless swelling on the upper lip. A painless, non-tender, well-circumscribed, slightly mobile, sessile, nodular, and rubbery (in consistency) tumor measuring 5.0 cm x 2.0 cm was noted on the left side of his upper lip. The overlying skin was not fixed and of normal color. There was no ulceration, and palpation did not elicit pain or bleeding. There was no history of trauma. Blunt dissection was used to completely excise the nodular, whitish, and encapsulated tumor. Microscopy showed a well-circumscribed and partly encapsulated biphasic lesion, with large lobules of myxo-chondroid stroma and intervening cellular nodules of basaloid cells, well-formed tubules containing eosinic secretion, and nests of myoepithelial cells. A diagnosis of PA (benign mixed tumor) was confirmed.

CONCLUSION

Blunt dissection is indicated to preserve the cosmesis and function of the upper lip.

Key Words: Pleomorphic adenoma, Upper lip, Minor salivary gland tumor, Benign mixed tumor, Case report

Core Tip: Salivary gland tumors are relatively rare. Pleomorphic adenoma (PA) (benign mixed tumor) is the most common benign tumor of the salivary glands. It comprises about 3%-10% of all head and neck tumors and 50% of the major and minor salivary gland neoplasms. Among minor salivary gland tumors, the palate is the most common site of predilection (42.8%-68.8%), followed by the upper lip (15%-20%). PA of the upper lip is relatively rare. Our case report is on the clinical presentation, histopathology, and management of PA (benign mixed tumor) of the upper lip.

INTRODUCTION

Pleomorphic adenoma (PA), or mixed tumor, is the most common benign tumor of the salivary glands. In the head and neck area, it comprises about 3%-10% of all head and neck tumors and 50% of the major and minor salivary gland neoplasms[1]. PA of the minor salivary glands occurs in the palate (67.5%), lips (10%), cheeks (5%), tongue (2.5%), and other sites (15%); PA in a lip is relatively rare[1,2]. The hard palate is the most common site of predilection (42.8%-68.8%), followed by the upper lip (15%-20%), cheek (5.5%), throat (2.5%), and retromolar region (0.7%)[2]. PA rarely affects the cheek mucosa, lip, and tongue. PA can also occur in ectopic sites such as the floor of the mouth and alveolar mucosa, Stenson’s duct, accessory parotid tissue, mandible, tonsillar tissue, lower neck, middle ear, sternoclavicular joint, thyroglossal duct, and parapharyngeal space[1-3]. PA presents clinically as a well-defined, asymptomatic, slow-growing, firm, nodular, rubbery lesion[4-6]. Women between 40 and 50 years (with a mean age of presentation of 43-46 years) are commonly affected with a female-to-male ratio of 1.4:1[5]. However, a systematic study by Almeslet showed a female predilection with a male-to-female ratio of 8:13[6]. PA is characterized by a single cell differentiating into three components: An epithelial component, a myoepithelial component, and a mesenchymal component[6]. This manifests histologically as a variable pattern of the epithelium in a loose fibrous stroma of myxoid, chondroid, or mucoid type with myoepithelial cells of polygonal shape with a pale eosinophilic cytoplasm[6]. The exact etiology of PA remains unclear, cells of origin are thought to be reserve cells from intercalated ducts, and cytogenetic and molecular studies have implicated chromosomal aberrations of 8q12 and 12q15[7]. Microscopic examination clinches the diagnosis.

We are reporting a 28-year-old man who presented with a PA of the upper lip that had been growing slowly for the past year.

CASE PRESENTATION

Chief complaints

A 28-year-old male patient presented at our Oral and Maxillofacial Surgery Clinic with a chief complaint of a painless swelling on the left side of the upper lip.

History of present illness

The swelling had been growing slowly for the past 3 years.

History of past illness

There was no history of trauma.

Personal and family history

The patient’s medical, dental, and family history was non-contributory.

Physical examination

The tumor appeared to be superficial to the orbicularis oris muscle as the patient had a full mouth opening with no asymmetry or limitation. Extra oral examination showed a painless, well-circumscribed tumor, slightly mobile, sessile, nodular, and rubbery (in consistency) tumor measuring 5.0 cm × 2.0 cm (Figure 1A). The overlying skin was of normal color.

Figure 1 View of the patient and surgical specimen. A: Profile view of the patient on presentation; B: Surgical specimen.

The skin over the tumor was not fixed. There was no ulceration, and palpation did not elicit pain, fluctuation, or bleeding. Submandibular, mental, and cervical lymph nodes were not palpable. The intraoral mucosa under the tumor was of normal color.

FINAL DIAGNOSIS

Histopathology examination confirmed the lesion as a PA (benign mixed tumor).

TREATMENT

The tumor was excised under local anesthesia using 2% lignocaine with 1:100000 adrenaline hydrochloride. Lignocaine was injected around the tumor and a 4.0-cm-long incision was made over the middle of the vermilion border. Blunt dissection was used to excise the tumor. The excised tumor was nodular, whitish, and encapsulated (Figure 1B). The incision site was closed using Vicryl 4/0. The patient tolerated the procedure well. The surgical specimen was sent to a histopathology laboratory for examination. Macroscopically, the firm whitish tissue measured 3.5 cm × 2.5 cm × 2.0 cm, weighing 7.5 g. Microscopic examination (Figure 2) showed a well-circumscribed and partly encapsulated lesion that is biphasic. Large lobules of myxo-chondroid stroma and intervening cellular nodules of basaloid cells that are rather cohesive, elsewhere well-formed tubules containing eosinophilic secretions, and nests of myoepithelial cells were noted. These features are the typical appearances of a PA (benign mixed tumor). The excision of the lesion appeared complete. Figure 3 shows the patient 6 wk post-surgery. Normal upper lip anatomy has been restored and the patient is pleased with his appearance.

Figure 2 Epithelial nests and tubules associated with sheets and clusters of plasmacytoid myoepithelial cells embedded in a chondromyxoid matrix. A: Haematoxylin and eosin (H&E) staining, × 40 magnification; B: H&E staining, × 100 magnification; C: H &E staining, × 200 magnification.

Figure 3 View of the patient 6 wk post-surgery.

OUTCOME AND FOLLOW-UP

The 3-mo post-surgery review showed that satisfactory healing had been achieved and the patient was pleased by the appearance of his lip.

DISCUSSION

The average size of lip PAs was 1.5 ± 0.7 cm (range, 0.7-2.2 cm). PA (benign mixed tumor) is the most common benign tumor of the major salivary glands with a predilection for the parotid glands. Minor salivary gland tumors, benign and malignant, constitute 18% of salivary gland tumors[7,8]. However, tumors in the minor salivary glands are uncommon, with PA accounting for nearly 40% of them, and common in the palate[7]. PA has a female preponderance in the third and fourth decades with an average of 33.2 years. In our case, the upper lip PA developed in a 28-year-old man. This is in keeping with the occurrence of upper lip PA in young patients. PA of the lip with external cutaneous skin involvement but with no mucosal involvement is extremely rare[8,9]. This is similar to our case which had no oral involvement. The upper lip has a propensity for benign tumors as opposed to the lower lip where malignant tumors are more common. PA on the lip is more common in the upper lip than in the lower lip with a ratio of 6:1[7,10]. However, this tends to vary with centers where the report comes from[8,11,12]. Umemori et al[12] found that 11.8% of the PAs occurred on the lips, of which 9.8% were distributed on the upper lip and 2.0% on the lower lip. For preoperative diagnostic assistance, ultrasonography and magnetic resonance are useful. No imaging was used in our case. An excisional biopsy was performed in our case and a histopathology examination confirmed the diagnosis as PA. Histopathology features of PA of the lip are similar to those of PA from other sites in that they comprise epithelial and mesenchymal cells arranged in diverse patterns and embedded in the mucoploysachaccharide stroma[7,8]. Differences in embryonic development may account for the differences in affliction by benign and malignant conditions[11]. The majority of intraoral lip PAs tend to present as well-circumscribed, nodular, mobile, sessile, rubbery mass covered with a normal oral mucosa in younger patients. Our case was extraoral on the upper lip, similar to the one described by Gelidan and Arab[8]. The clinical differential diagnosis of swelling of the lips is inclusive of cystic diseases (mucocele, dermoid cyst, and epidermoid cyst), benign tumors (fibroma, hemangioma, lipoma, and schwannoma) and malignant tumors (squamous cell carcinoma, mucoepidermoid carcinoma, and adenoid cystic carcinoma), foreign body, infection, orofacial granulomatosis, Quincke’s edema, tuberculosis, and actinomycosis[12]. Complete wide surgical excision is the treatment of choice to minimize recurrence and possible malignant transformation, such as carcinoma ex PA, should the lesions be left unattended for a long time. Recurrences may occur several years after surgery.

CONCLUSION

There are few reports on upper lip PA in the literature. Our case report adds to the knowledge of the clinical presentation, diagnosis, and management of upper lip PA.

ACKNOWLEDGEMENTS

Gratitude to Mr. Sibve for the photography.