Benign neural lesions of the oral and maxillofacial complex: a 48-year-retrospective study

Universidade Federal do Rio Grande do Norte (UFRN), Natal, Rio Grande do Norte, Brazil

DOI: 10.5935/1676-2444.20200002

Corresponding author

Roseana de Almeida Freitas
ORCID 0000-0002-7577-5375
e-mail: roseanafreitas@hotmail.com

INTRODUCTION

Peripheral nerve sheath lesions are among the various diseases that can affect the nervous tissue. These include benign and malignant reactive or neoplastic processes that develop from the proliferation of the nerves themselves (axons and Schwann cells) or from their limiting sheaths, and diagnoses can sometimes be challenging⁽¹⁾. These neural origin lesions may occur in the maxillofacial region, although they are rare^{(2, 3)}.

In this context, benign tumors include traumatic neuroma, neurofibroma, neurilemoma, granular cell tumors, congenital epulis, and solitary circumscribed neuroma^(3-5). Although rare, the association of some of these lesions with clinically relevant syndromes, such as neurofibromatosis, have been reported⁽⁶⁾.

The most noteworthy benign neural neoplasms that affect oral tissues are neurofibroma and neurilemoma. Neurofibroma is the most common type of peripheral nerve neoplasm, characterized by Schwann and perineural cell and endoneurial fibroblast proliferation⁽⁷⁾. These neoplasms are rare and represent 28.6% to 29% of the neural lesions that occur in the oral and maxillofacial complex^{(3, 4)}. When present in the oral cavity, these lesions occur mainly on the tongue, jugal mucosa, lips, palate, and gingiva. In rare cases, intraosseous neurofibroma may be present^(8-10).

Neurilemomas, also named Schwannomas, were first described by Verocay in 1910, and they are typically a well-circumscribed, slow-growing neoplasm displaying preference for the tongue and lips in the oral cavity⁽¹¹⁾. They are exclusively composed by neoplastic Schwann cells⁽¹²⁾ and are very uncommon, although about 25% to 48% of all cases affect the head and neck region⁽¹³⁾.

Retrospective studies that address clinical and pathological benign peripheral nerve sheath lesion characteristics are important to contribute for a better understanding of patients affected by these lesions, as well as their clinical manifestations. In this context, the aim of the present study is to analyze a 48-year epidemiological data from a series of benign neural lesions of the oral and maxillofacial complex diagnosed at a reference anatomical service in northeastern Brazil, carrying out comparisons to literature data.

METHODS

This study was approved by the Research Ethics Committee (Number 2,167,121) of the Universidade Federal do Rio Grande do Norte (UFRN). The study comprised a descriptive and retrospective analysis of clinical data contained in the medical records of patients diagnosed with benign oral lesions of neural origin diagnosed and filed at the UFRN Dentistry Department, from 1970 to December 2017. This is one of the oral and maxillofacial pathology reference centers in Brazil and the main center in Rio Grande do Norte state.

Data regarding patient age and sex and lesion location, aspect, size, color, symptomatology, and treatment were compiled from the clinical data associated with the biopsy records. All cases associated with histopathological reports of any benign neural lesion containing information in clinical records or electronic databases were included, while cases presenting less than 10% of the relevant clinical information were excluded.

The information contained from patient records include consultation year, sex and age. Lesion-related parameters comprised anatomical location, lesion aspect, size, color, symptomatology and treatment (excisional biopsy, incisional biopsy, and associations). Ethnicity was not considered, since the Brazilian population is composed of an extensive mixture of Amerindians, Europeans, and Africans⁽¹⁴⁾ and no racial categorization would reflect the true ethnic distribution of the patients, making it difficult to compare this variable to other studies. Obtained data were tabulated in a spreadsheet and a descriptive statistical analysis was performed.

RESULTS

A total of 15,527 different pathological processes were registered at the UFRN Dentistry Department during the 48-year study period. From this total, 60 (0.37%) comprised tumors of neural origin, distributed in the following histological types: 24 (42.11%) neurofibromas, 15 (26.32%) traumatic neuromas, nine (15.79%) neurilemomas, three (5.26%) granular cell tumors, three (5.26%) congenital epulis and three (5.26%) solitary circumscribed neuromas (Table 1).

Males were the most frequently affected by neurofibroma, whereas females were the most affected in all other processes evaluated, except for solitary circumscribed neuroma, which affected both males and females to the same extent. Patient age group varied considerably according to lesion diagnosis, where cases diagnosed as congenital epulis affected infants by approximately six days of age, while traumatic neuroma was diagnosed in patients presenting, on average, 60.5 years old (Table 1). From the 24 neurofibroma cases evaluated here, only three (12.5%) were associated with type I neurofibromatosis.

Regarding lesion size, most ranged between 1 cm and 4 cm, and a nodular aspect was most frequently documented. Painful symptomatology was an uncommon finding, present only in five (33.3%) traumatic neuroma cases and in one (11.1%) neurilemoma case (Table 2). Surgical excision was the most frequently documented treatment (Table 2).

DISCUSSION

Peripheral nerve sheath lesions are rarely found in the oral cavity^{(3, 4)}. Among the most common benign neoplasms are traumatic neuroma, schwannoma or neurilemoma, and neurofibromas. However, other, rarer benign tumors may also occur, including granular cell tumor, congenital epulis and solitary circumscribed neuroma⁽¹⁵⁾. In the present study, neural lesions corresponded to only 0.37% of the 15,527 cases comprising different types of lesions diagnosed at the UFRN Pathological Anatomy Service during the 48-year study period, demonstrating the low frequency of these lesions in the oral and maxillofacial complex.

Unlike the present study, which indicated neurofibroma as the most common lesions, Alotaibi et al. (2016)⁽³⁾ and Salla et al. (2009)⁽⁴⁾ point to a higher occurrence of traumatic neuroma. Patient age, regardless of lesion histological type, varied from three days to 79 years old, indicating that these lesions may occur over a wide age range. The results reported by Salla et al. indicate that most cases were detected in female patients (71.43%), as also observed in the present study. Neurofibroma is a benign neural proliferation consisting of Schwann cells, perineural cells, and fibroblasts which, in the oral cavity, may occur in solitary or multiple forms, associated or not with neurofibromatosis type 1^{(4, 7)}. Although these neoplasms may be associated with syndromes, most lesions are sporadic^{(16, 17)}, as observed herein, in which, only three cases (12.5%) from a total of 24 were associated with type 1 neurofibromatosis.

Patients presenting neurofibroma in the present study were mostly male (66.6%), ranging from 10 to 77 years of age, with mean age of 39.1. The findings observed herein regarding the most affected age group are similar to those reported by Campos et al. (2012)⁽¹⁶⁾, who reported mean age of 38.5. However, those authors observed a predominance of women (72.7%) in the study population.

Clinically, neurofibroma envolve, mainly, the tongue, lips and jugal mucosa, and are less frequent on the gingiva, palate and maxillary bones^{(16, 17)}. In the present study, most cases were observed on the tongue and alveolar ridge, with no symptomatology. As neurofibroma clinical aspects are analogous to many other oral cavity lesions, a biopsy is mandatory to obtain an accurate diagnosis^{(16, 18)}.

Some studies indicate that most patients presenting traumatic neuroma, neurofibroma and granular cell tumor are women^{(2, 4, 19)}. The present study is in accordance with these findings in relation to traumatic neuroma and granular cell tumor, which were present, in 80% and 66.66% of women respectively, unlike neurofibroma, which mostly affected men.

Traumatic neuroma are most frequently observed on the tongue and lips⁽³⁾ usually associated with trauma reports. In the present study, these tumors affected adults with a mean age of 60.5. Neurilemomas are observed in several areas but are frequent on the lips⁽¹¹⁾. Granular cell tumors are more frequent on the tongue^{(3, 19)}, corroborating the present study and the results reported by Franco et al. (2017)⁽⁵⁾.

Most lesions ranged from 1 cm to 4 cm in size, in agreement with data reported by Franco et al. who reported mostly small lesions. However, tumors measuring 3 cm or greater were detected among neurilemoma, traumatic neuroma, neurofibroma, and granular cell tumor cases. All cases presented a nodular appearance, with almost no symptomatology. Solitary circumscribed neuroma corresponded to three cases only, corroborating their rarity in the oral cavity, as reported by the relevant literature^{(3, 5)}.

In general, most lesions are treated by surgical excision, but, in the case of neurofibroma, all patients should be clinically evaluated concerning the possibility of association with neurofibromatosis⁽¹⁵⁾. If this association is confirmed, the risk of malignant transformation of these lesions should be considered, which occurs in 5% to 15% of cases^{(1, 3)}.

CONCLUSION

Benign neural lesions in the maxillofacial complex are rare and the clinical profile of the patients observed in the present study was consistent with data commonly reported in the literature. This study suggests that these lesions present predominantly as asymptomatic nodules and are mostly treated by surgical excision. In general, this study promotes knowledge of epidemiological data by dentistry professionals, which is essential for the correct diagnosis and treatment of patients presenting these lesions, as well as for differential diagnosis concerning other types of lesions.

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