Swelling on lower lip…not always a mucocele !!!

Schwannomas are well characterized uncommon neural neoplasms which may rarely present with variation in clinical manifestation. Oral Schwannomas clinically simulate other lesions like traumatic fibroma, pyogenic granuloma, mucocele and salivary gland lesions. The diagnosis of schwannoma is typically made at the time of surgery following biopsy and surgical resection is the mainstay of treatment with no chances of recurrence as they are well encapsulated. We present a case of schwannoma of lower lip occurring in a 21-year-old female patient.

INTRODUCTION

Peripheral nerve sheath tumors (PNST) are benign or malignant lesions of neural origin. Neurofibroma is most common followed by schwannoma (neurilemmoma/neurinoma), palisaded encapsulated neuroma, traumatic neuroma and others.[1] Schwannomas are common, slow growing tumors of the sheath of peripheral nerves, arising from the Schwann cells. Approximately 25-45% of Schwannomas are more common in head and neck region and are rarely found in oral cavity comprising about only 1%. Most of the intraoral schwannomas occur on the tongue[23] followed by buccal mucosa, palate,[4] lip etc.[5] Intraosseous schwannomas are also reported in literature.

Neurilemmoma is considered to be arising in association with a nerve trunk. As it grows, it pushes the nerve aside and usually the mass is asymptomatic in nature.[1] Histopathologically schwannoma has classical feature which is rarely mistaken for other lesions/tumors.

CASE REPORT

A female patient of 21 years presented with a slow-growing, painless swelling on lower lip of six months duration. Examination revealed a 1 cm × 1 cm, dome shaped, non-tender, firm to soft mobile mass with a smooth surface, on the left side of lower lip. The margins were well demarcated [Figure 1]. There was no neurological deficit and no neck nodes palpable. The differential diagnosis for the lesion was benign fibrous overgrowth and organizing mucocele. Therefore, initial biopsy and imaging studies were not performed. She underwent excision of the lesion under local anaesthesia under aseptic precautions. Curvilinear incision at the posterior border of lesion was given to expose the lesion, lesion was separated with help of blunt dissection [Figure 2] followed by complete excision of lesion and primary closure was carried out [Figure 3]. Intraoperatively the mass appeared well encapsulated [Figure 4] and mass was easily separable from the surrounding tissues. The mass was totally excised and the surgical specimen was an ovoid soft tissue mass with a thick capsule [Figure 4]. The patient had an uneventful postoperative recovery.

Figure 1 and 2:

(1) Preoperative lesion (2) Exposure

Figure 3 and 4:

(3) Closure, (4) Specimen

Histopathology of the specimen [Figure 5] revealed that tumor was encapsulated with spindle cell lesion showing two different pattern of growth of Schwann cells i.e., Antoni A and Antoni B. Predominant pattern was Antoni A displaying spindle cells closely packed together with palisading of nuclei. Verocay bodies were also present. Thus histopathological diagnosis was consistent with schwannoma.

Figure 5

Photomicrograph showing a well circumscribed tumor showing fibrous connective tissue capsule. Antoni A tissue dominant (H and E with 10× magnification)

DISCUSSION

Schwannoma usually occurs in adults of a younger age group, although they can affect children. There is equal gender predilection. The tumor is usually asymptomatic. Unlike neurofibromas, schwannomas rarely metastasise.[6] Schwannomas occurring intra-orally (about 1%)[78] constitute 45.2 to 52% on tongue, 13.3% on cheek, 19.86% on buccal/vestibular mucosa and 19.24% on lip and gingiva, hence occurrence of schwannoma on lower lip is rare.[910]

Soft tissue swellings of lower lip invites the inclusion of traumatic fibroma (focal fibrous hyperplasia) and mucocele as the first candidates in list of provisional diagnosis, however in reported case there was no history of variation in size of lesion, paraesthesia, regional malposed teeth, and traumatic habitual lip biting which negated the diagnosis of these lesions. The lesion in present case was smaller in size, firm and long standing in nature. The firm but long standing schwannomas with larger size are known to develop cystic degeneration which renders them soft in consistency. Clinically, such schwannomas are designated as ancient schwannomas.[11] In cases of schwannomas the recurrence rates are very low since these tumors are encapsulated. Cases of multiple schwannomas are also reported to occur. Central neurilemmoma simulate tumors or neoplasms of odontogenic/non-odontogenic tumors of head and neck region in their clinical presentation. They have a low risk of metastasizing and do not usually present with underlying systemic disease, such as neurofibromatosis.[9]

Summary

This case report illustrates the rare site of presentation of schwannoma occuring on lower labial mucosa which was diagnosed and managed efficiently at initial stage in our institute.