Background and Objectives: Benign tumors of the external auditory canal (EAC) are rare among head and neck tumors. The aim of this study was to analyze the clinical features of patients who underwent surgery for an EAC mass confirmed as a benign lesion. Methods: This retrospective study involved 53 patients with external auditory tumors who received surgical treatment at Korea University, Guro Hospital. Medical records and evaluations over a 10-year period were examined for clinical characteristics and pathologic diagnoses. Results: The most common pathologic diagnoses were nevus (40%), osteoma (13%), and cholesteatoma (13%). Among the five pathologic subgroups based on the origin organ of the tumor, the most prevalent pathologic subgroup was the skin lesion (47%), followed by the epithelial lesion (26%), and the bony lesion (13%). No significant differences were found in recurrence rate, recurrence duration, sex, or affected side between pathologic diagnoses. The overall recurrence rate after excision was 11% and higher in patients with fibro epithelial polyp, intra epidermal pilarepithelioma, and chronic inflammation. Culture of otorrhea identified pathogens in half of patients with recurrence, and the recurrence rate was considerably higher (50%) in cases confirmed to be infected by microorganism. Conclusion: Our results indicated that nevus was the most common pathologic diagnoses. The overall recurrence rate was 11%. Benign external auditory canal lesions that originate from the epithelium and bony canal should be observed closely in the postoperative follow-up period. Furthermore, treatment of infection is thought to be important for preventing recurrence.

• External auditory canal

• Benign tumor

• Surgical excision

• Recurrence

• Infection

Kim JR, Im H, Chae SW, Song JJ (2017) Clinical Features of Benign Tumors of the External Auditory Canal According to Pathology. Ann Otolaryngol Rhinol 4(3): 1169.

EAC: External Auditory Canal; MSSA: Methicillin-sensitive Staphylococcus aureus

Benign tumors of the external auditory canal (EAC) are uncommon among head and neck tumors. The EAC begins at the opening of the cup-shaped portion (concha) of the ear, and extends downward to the tympanic membrane. The adult EAC measures 2-3cm in length. The EAC is covered with keratinizing stratified squamous epithelium. The skin over the lateral portion is thicker and contains a subcutaneous layer, hair follicles, sebaceous glands, and wax-secreting ceruminous glands. These skin appendages are absent in the medial two thirds of EAC, where the bony wall is closely adherent to the underlying periosteum [1]. Chronic irritation and inflammation have been considered as causative factors in EAC tumor; however, conclusive evidence of this is lacking [2]. Symptoms are rare but can include conductive hearing loss, otalgia, otorrhea, vertigo, and tinnitus. In previous studies, osteomas were the most commonly found pathologic type in EAC [1,3]. Spielmann et al. reported a 10- year case series of 48 surgically resected EAC masses, including malignant tumors, benign tumors, infective lesions, and epithelial abnormalities. In their study population, bony lesions were the most frequently encountered diagnosis of EAC benign tumors [1]. Wiatr et al. also retrospectively investigated 26 benign EAC tumor cases, and osteoma was the most common pathologic diagnosis [3]. However, there are no concrete data supporting this conventional idea, especially in Asian countries. Furthermore, the prevalence and clinical aspects of various pathological benign tumors arising from the EAC have not yet been investigated with sufficient sample size. The purpose of this study was to describe the correlation of pathologic diagnoses with clinical features in surgically removed benign tumors of the EAC.

From 2003 to 2014, a retrospective, single-center study of EAC lesions was performed using the medical records of patients who had received surgical treatment for EAC tumors at Department of Otorhinolaryngology-Head and Neck Surgery, Korea University Guro Hospital. A total of 53 patients (26 male and 27 female) were included in the present study. All study protocols were approved by the Institutional Review Board of Korea University Guro Hospital (KUGH15144-001). EAC masses were identified with rigid otoendoscopy, and discovered lesions were surgically excised under and general anesthesia in an operating room. Medical records were reviewed for patients’ age, sex, affected side, pathologic diagnosis, operation records, concurrent infection, and recurrence. Patients were classified into one of five categories according to tumor origin (bony, epithelial, skin, inflammatory and other benign lesions). The epithelial lesion means the diseases in the most superficial layer of skin, stratified squamous epithelium. And skin lesion was defined as the lesions which arise in the dermis and skin appendages excluding epithelium. Statistical analyses were performed using the Statistical Package of the Social Sciences (SPSS, version 21). Results related to patient age are expressed as means (standard eviations, SDs).

Patient characteristics

From 2003 to 2014, a total of 53 patients were diagnosed with EAC tumor under otoendoscopy; all patients underwent excision. Baseline characteristics are shown in Table (1).

Table 1: Characteristics of patients with benign EAC tumors.

There were 26 male and 27 female patients, with an average age of 37.0 ± 19.2 years. The right side was affected in 26 patients, and the left in 27 (Table 1). Patients with small EAC tumors had no symptom in many cases, however, patients with large EAC tumors complained of earfulness. In the case of inflammation, otalgia or otorrhea was frequently observed.

In 47 cases, tumors were simply excised via an endaural approach. In 4 patients, canaloplasty was performed with excision; 2 of these also underwent tympanoplasty. In one case, pathologically confirmed as a branchial cleft anomaly, a postauricular approach was used because of the large size of the mass (3×3cm). Statistical analysis revealed no significant differences in age, sex, affected side, recurrence rate, and recurrence duration between the pathologic diagnoses (P > 0.5).

Incidence

In this case series, nevus was the most common pathologic diagnosis. There were 21 patients diagnosed with nevus (40%), followed by osteoma (7 patients, 13%), EAC cholesteatoma (7 patients, 13%), chronic inflammation (6 patients, 11%), epidermal cyst (5 patients, 9%), and others. Among the 21 nevus patients, there were 19 intradermal (90%), 1 compound (5%), and 1 junctional (sebaceous) pathologic types. The most prevalent pathologic subgroup was the skin lesion (25 patients, 47%), followed by the epithelial lesion (14 patients, 26%), and the bony lesion (7 patients, 13%) (Table 1).

Recurrence

During the postoperative follow-up period, recurrent lesions were identified under otoendoscopic evaluation in 6 patients (6 of 53, 11%). The mean follow-up period was 18.4 months. The recurrence rate was 28% (2 of 7) in patients with osteoma, 20% (1 of 5) in those with epidermal cyst, and 17% (1 of 6) in those with chronic inflammation. All patients who were diagnosed with fibro epithelial polyp or intra epidermal pilar epithelioma experienced relapse and underwent re-excision. In one fibro epithleial polyp patient, the tumor recurred twice, necessitating a second revision surgery.

Among the pathologic subgroups, the recurrence rate was highest in the bony lesion group (29%) followed by the epithelial lesion group (21%) and the inflammatory lesion group (17%). In the skin lesion group, no patients experienced recurrence after excision. The average duration of recurrence was 16.5 months, and it was the longest in patients with osteoma (45 months). No patients experienced malignant transformation during the follow-up period.

Infection

We performed bacterial culture of otorrhea preoperatively. Pathogens were confirmed in 6 patients (11%); among these, 3 (50%) had Pseudomonas aeruginosa, and 3 (50%) had methicillin-sensitive Staphylococcus aureus (MSSA). Half of these patients (3 of 6) had re-excision. Three of six recurrent cases also had confirmed pathogens (Table 2).

Table 2: Characteristics of patients with recurrence of benign EAC tumor.

Benign tumors originating from the EAC are uncommon and usually asymptomatic; thus, most of them are found incidentally. But they can sometimes cause aural symptoms such as ear fullness, conductive hearing impairment, otitis externa, otalgia, and tinnitus. Surgical removal is the standard treatment. It has also been suggested that ear symptoms assumed to be due to EAC tumor could be alleviated by tumor excision [4].

In this study, occurrence of EAC tumor was not associated with sex or age; this finding is similar to those of other reports [5]. In previous studies, bony lesions (eg, osteoma, exostoses) were found to be the most common pathologic types of benign EAC tumors [1,3]. However, nevus was the most common form of EAC tumor in this study.

Nevus, one of the most common benign skin tumors, is a sharply-circumscribed overgrowth of cells associated with melanocytic migration and proliferation [6]. It usually has a uniform surface and coloration pattern, round or oval shape, and relatively regular border (Figure 1A,B).

Figure 1: Otoendoscopic findings of each pathologic type. A. Nevus (compound type), B. Nevus (intradermal type), C. Osteoma, D. Fibroepithelial polyp, E. Epidermal cyst, F. Chronic inflammation.

Most cases are acquired in childhood and puberty and peak in the fourth decade of life [7]. (In this case series, the average age was 39.6 years in the nevus group.) Histologically, nevi are divided into three subtypes according to the location of clusters of melanocytic cells; junctional nevus in the epidermis, intradermal nevus in the dermis (Figure 2A) and compound nevus in both areas. Flat junctional nevi have darker pigmentation, whereas more elevated compound nevi have a lighter brown to black color (Figure 1A). Intradermal nevi are elevated lesions without pigmentation (Figure 1B). Lim et al. reported that the intradermal type was the most common among EAC nevi; the same tendency was shown in this study [8].

Some have insisted that acquired EAC nevi must be removed in all cases, or if symptoms are evident [9]. After incomplete removal, nevi may reappear as recurrent lesions (pseudomelanoma), clinically and pathologically similar to malignant melanoma in situ regardless of the initial pathology [10]. Early and complete resection should thus be recommended for EAC nevi. In this study, no nevus patients experienced relapse. Nevus is one of the most frequently acquired skin neoplasms in Caucasians. Most Caucasian adults have about 20 nevi but is less common in Black individuals or other persons with highly pigmented skin [11]. Because this review involves only South Korean patients of Asian ethnicity, further study on interracial differences of EAC nevi is recommended. The clinical presentation of osteoma in the EAC is a solitary, slow-growing, and pedunculated mass in the unilateral bony canal [2,12] (Figure 1C). It is known to arise from tympanomastoid and tympanosquamous suture lines after persistent or repetitive exposure of the ears to cold water [13]. Recurrence had occurred in 2 of 7 osteoma patients 45 months after the first excision. The recurrence rate of osteoma is much higher than overall rate for EAC tumors, and the duration of recurrence is also longer than average (16.5 months). Long-term follow-up is therefore recommended for bony lesions in EAC. In this study, one case was diagnosed as a fibro epithelial polyp (Figure 1D) and recurred twice, so the patient underwent surgical excision two times. Fibroepithelial polyp is a benign lesion of mesodermal origin that is most commonly found in the skin and genitourinary tract, but very rarely in the EAC. Their etiology is thought to be an underlying chronic inflammatory process, but remains largely unknown [14,15]. In EAC, fibro epithelial polyp was assumed to be a secondary, reactive change in the skin to an initial inflammatory change or an osteoma [4,6]. Figure 2,

Figure 2: Microscopic findings of each pathologic type. A. Nevus (intradermal), view of melanocyts with brown pigmentation (arrow), (x100) B. Fibroepithelial polyp, solitary, pendunculated growth pattern, benign squamous epithelial lining with moderate acanthosis (white arrow), mild papillomatosis (black arrow) (x40) C. Fibroepithelial polyp, view of fibrotic backgrounds (white arrow) with vessels (black arrow), (x200).

B and C show the histopathologic characteristics of fibro epithelial polyp. It presents a solitary, pendunculated growth pattern and has benign squamous epithelial linings with moderate acanthosis and mild papillomatosis [16]. In our study, the fibroepthelial polyp case had no clinical findings suggesting history of aural polyp or other ear disorders, or mechanical stimulation of the EAC. Tanaka et al. reported the first known case of independent fibroepithelial polyp of the EAC [5]. In epithelial lesions, epidermal cyst presents as a solitary, rounded mass that has an epidermallike wall (Figure 1E). A chronic inflammatory mass in the EAC has an erythematous nodular appearance (Figure 1F). The overall recurrence rate was 11% (6 of 53); incomplete resection of the tumor was thought to be the main cause of relapse. Furthermore, culture of otorrhea identified pathogens in half of patients with recurrence, and the recurrence rate was considerably higher (50%) in cases confirmed to be infected by microorganism. This suggests that infection may increase the risk of recurrence of EAC tumor. Further research should clarify the causal relationship of tumor recurrence and infection in a larger sample size.

This study has some limitations. First, only patients treated surgically were included in this case series; patients who had conservative, medical management or were lost to follow-up were excluded, which could represent a selection bias. Second, the sample size is relatively small. Although the sample size of this analysis is larger than that of any other previous studies of benign EAC benign tumors [1,3], it is still insufficient to clarify the strong correlation between pathologic diagnoses and clinical characteristics. Third, this study was performed only in South Korea and thus does not reflect interracial, regional, and environmental differences. In the future, a larger, multicenter study should be performed to get a more meaningful, powerful result.

In conclusion, our results indicated that nevus was the most common pathologic type, and the overall recurrence rate  was 11%. There were no significant differences in age, sex, affected side, recurrence rate, and recurrence duration between pathologic diagnoses. Benign EAC lesions that originate from the epithelium and bony canal should be observed closely in the postoperative period. Treatment of infection is also thought to be important for preventing recurrence.

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