Postauricular Myofibroma of the Facial Canal: A Case Report
Article information
Abstract
Myofibromatosis is a proliferative disorder characterized by the development of soft tissue neoplasms referred to as myofibromas that predominantly occur in infants and young children. These lesions have been described using varied terminologies since they were first reported in 1951. However, these neoplasms are histopathologically characterized by benign fibroblast and myofibroblast proliferation containing a biphasic presentation of spindle-shaped cells surrounding a central zone of less differentiated cells arranged in a hemangiopericytoma-like pattern in all cases. Usually, myofibromatosis occurs in children aged <2 years and is observed at birth in nearly 60% of cases. We report a rare case of myofibroma in an 8-year-old boy who presented with an approximately 6-month history of a left postauricular mass. Histopathological evaluation of the resected mass confirmed the diagnosis.
Introduction
Myofibromas, an uncommon benign form of spindle cell neoplasm, is most commonly found in the dermis and subcutaneous region of the head and neck. It may present as a solitary or multicentric lesion, and while benign, may show aggressive behavior and lead to local bony destruction or invasion. With the vast majority of cases presenting before 2 years of age, certain uncommon presentations of this lesion may complicate diagnosis [1]. Since myofibromas share many features with other spindle cell neoplasms, both benign and malignant, which have vastly different treatment protocols, it is important to recognize their unique radiological and histopathological characteristics to ensure accurate diagnosis and appropriate treatment [2]. Surgical excision of masses in the postauricular region requires surgeon-specific head and neck knowledge to minimize any functional consequences, especially regarding important surrounding structures such as the internal carotid artery and the facial nerve. If the mass had an intracranial extension, a multidisciplinary team should be formed including a neurosurgeon [3]. We report a case of myofibroma in an 8-year-old boy complaining of a left postauricular mass.
Case Report
An 8-year-old otherwise healthy male patient presented to our tertiary center with a left postauricular mass, noticed by his family 6 months ago. The mass increased in size gradually over time, however, it was not associated with any other symptoms. Examination in the clinic showed a large, firm, immobile, non-tender mass arising from the left postauricular region, with no overlying skin changes, extending to the posterior triangle of the neck. There was also an associated narrowing of the patient’s left external auditory canal, seemingly due to an extension of the mass as seen in Fig. 1.
Preoperative left postauricular mass.
The patient was admitted for further investigations and underwent computed tomography (CT) and magnetic resonance imaging (MRI) scans of the head and neck with intravenous contrast. His CT scan revealed a well-defined lobulated soft tissue mass originating in the left postauricular region, containing foci of punctate calcification (of which some contain central lucencies) (Fig. 2A). His MRI scan similarly reported a well-defined lobulated soft tissue mass in the left postauricular region compressing the parotid gland anteriorly, abutting the left mandibular condyle posteriorly, and the left carotid space laterally, while minimally displacing the ear pinna laterally and extending into the lateral wall of the left parapharyngeal space. The mass showed low to intermediate T1 signal intensity, heterogeneous high T2 signal intensity, and intense enhancement on post-contrast images (Fig. 2B). The findings were concerning for hemangioma. Enhanced MRI images and relations with anatomical structures such as the carotid artery and the facial nerve can be shown in Fig. 2C and D.
Preoperative radiological findings. A: A CT scan of the temporal region shows a large left postauricular mass. B: A T2-weighted MRI of the brain reveals a well-defined lesion in the left postauricular region. C: A T2-weighted MRI of the brain illustrates important anatomical relations. D: An enhanced T1-weighted MRI shows the mass. CT, computed tomography; MRI, magnetic resonance imaging.
Accordingly, multiple punch biopsies were taken from the lesion for further evaluation. Microscopic examination showed a soft tissue lesion composed of bland spindle cells arranged in a fascicular and partly whorling pattern in a collagenous stroma. There were also associated foci of calcification with psammoma body formation. The tumor cells were positive for α-smooth muscle actin (SMA) immunostaining but negative for S100 immunostaining. As such, a histopathological diagnosis of spindle cell neoplasm was made, with myofibroma being the most likely diagnosis based on the morphology and immunohistochemistry of the lesion, and the decision was taken to completely excise the lesion.
Intraoperatively, an extensive left-sided postauricular mass was found extending to the stylomastoid foramen, compressing the facial nerve. The mass filled the parapharyngeal space and was in contact with the internal carotid artery. There was also erosion of the hypotympanic bone as well as part of the posterior canal wall, with the mass displacing the facial nerve inferiorly (Fig. 3). Complete excision of the mass was managed with preservation of the facial nerve, along with removal of the superficial lobe of the parotid gland and reconstruction of the eroded hypotympanum and posterior canal walls. Histopathological examination of the mass was in line with the previous report, thus confirming the diagnosis of postauricular myofibroma. Fig. 4 shows the histopathological characteristics of the excised mass and their reactivity to immunostaining.
An intraoperative left postauricular mass.
Histopathological findings. A and B: Soft tissue lesion composed of bland spindle cells arranged in fascicular and partly whirling pattern in a collagenous stroma (hemtoxyline & eosin, ×4). Multifocal calcification with psammoma body formation is seen. C and D: Tumor cells show positivity for SMA immunostaining (×4) while they are negative for S100 immunostaining (×4).
In the postoperative period, the patient suffered left-sided facial nerve palsy (grade 5 on the House–Brackmann scale) (Fig. 5A). His recovery was otherwise uneventful, and after 18 months his facial palsy was downgraded to grade 3 as shown in Fig. 5B.
Postoperative and follow-up images of the patient. A: Postoperative evaluation revealed grade 5 facial nerve palsy (House–Brackmann scale). B: At the 18-month postoperative follow-up, grade 3 facial nerve palsy was observed.
Discussion
Spindle cell neoplasms are a diverse collection of lesions comprising bundles of spindle cells, with wide-ranging implications depending on the type, with many lesions being malignant, others benign, and some just reactive in nature. Therefore, these neoplasms present a unique challenge to physicians, as differentiating these lesions from one another and arriving at an accurate diagnosis is critical for proper management while differentiating these lesions from each other often proves challenging. Commonly arising in the head and neck region, spindle cell neoplasms can range from spindle cell carcinoma, spindle cell melanoma, nodular fasciitis, vocal cord nodules, and sinonasal polyps, to myofibromas [4].
Myofibromas, in particular, are a benign uncommon form of spindle cell neoplasms commonly found in the dermis and subcutaneous tissue of the head and neck region. Myofibromas are usually present in either a solitary form or multicentric fibromatosis (with or without visceral involvement). While they are considered to be a benign process, in some cases, they may show aggressive and infiltrative behavior leading to bony destruction [5,6]. In both types, however, the vast majority are present before the age of 2 years, with 66% being noted at birth [6]. Our patient was unusual in his presentation at the age of 8 years, as well as the lesion involving structures surrounding the ear, with invasion of the hypotympanum and posterior external auditory canal wall.
While histopathological studies are required to diagnose myofibromas, imaging may be a useful addition in evaluating these lesions. Specifically, contrast-enhanced MRI scanning generally shows heterogeneous slight hyperintensity on T1-weighted imaging (variable signal intensity on T1), but T2-weighted images in all cases show heterogeneous hyperintensity. All tumors also showed marked enhancement on post-contrast images [7]. Similarly, MRI done for our patient showed low to intermediate T1 signal intensity, heterogeneous high T2 signal intensity, and intense enhancement on post-contrast images.
In order to accurately diagnose myofibroma, histopathological evidence is required. Myofibromas generally show a biphasic pattern or light and dark-stained areas, consisting of spindle cells arranged in short fascicles or whorls in the lightstained areas, with the darker-stained regions containing small spindle cells arranged around thin-walled, irregularly branching blood vessels. Immunohistochemical staining is critical for aiding in diagnosis, with myofibroma cells staining positive for SMA and vimentin, and negative for S100 and desmin [4,5,8-11]. Comparatively, histopathological examination in our patient revealed a collection of bland spindle cells arranged in a fascicular and partly whorling pattern in a collagenous stroma, with the tumor cells found to be positive for SMA immunostaining but negative for S100 immunostaining, thus aiding our diagnosis of myofibroma.
Management of myofibromas varies according to many factors. Solitary myofibromas often involute spontaneously, especially in infancy, and therefore expectant management can sometimes be enough. However, when the mass causes a cosmetic deformity or risks encroaching on vital structures, complete surgical resection is the preferred option. If surgery proves too risky, chemotherapy was found to be an option for reducing the size of the lesion, thus improving symptoms [5]. In our patient, the lesion caused a significant cosmetic issue. More importantly, there was a breach of important structures such as the hypotympanum and posterior canal wall, as well as a narrowing of the external auditory canal, and the mass encroached upon the facial nerve and internal carotid artery. Therefore, we decided that complete surgical excision was the preferred treatment choice.
Postoperative facial nerve palsy is a possible complication of surgery and has a poor aesthetic appearance, which can contribute to the development of social phobia and depression. Although the priority goes to patients’ well-being, more effort is being done on the postoperative appearance of the head and neck and the quality of life of patients [12]. Other surgeries that can cause this complication include parotidectomy and the excision of pediatric brain tumors [12,13]. Dealing with the facial nerve surgically is done via techniques such as the House–Brackmann approach, total rerouting, partial rerouting, and the fallopian bridge technique. A study by Chen, et al. [14] showed that the no-rerouting led to significantly better outcomes for the facial nerve. Still, a case-by-case approach should be considered for each individual patient [15]. To our knowledge, there is a lack in the literature about strategies specific to myofibroma excision in the postauricular area that are protective to the facial nerve.
While these lesions may be varied in presentation, as with our patient’s uncommon tumor location, it is important to be aware of the clinical, radiological, and histopathological features associated with myofibromas, and spindle cell neoplasms as a whole, to aid in properly diagnosing and treating these rare lesions.
In conclusion, head and neck myofibromas are rare neoplasms that could present with postauricular mass. Since the tumor can invade the facial nerve, early diagnosis is obligatory. The tumor does not have any unique radiological features and biopsy is the best way for diagnosis. While the mainstay treatment is excision for this type of tumor, further research is warranted for the treatment modalities.
Notes
Ethics Statement
Written informed consent from the patient’s guardian was obtained. Patient’s anonymity was preserved, eyes were covered in the photographs. This case report does not require an IRB review or approval per the Department of Health and Human Services (DHHS) guidelines.
Conflicts of Interest
The authors have no financial conflicts of interest.
Author Contributions
Conceptualization: Mohammad Al-Alawneh, Ra’ed Al-Ashqar. Data curation: Yazan Kanaan, Maulla Alali. Investigation: Haitham Odat, Mohammad Al-Alawneh. Methodology: Ra’ed Al-Ashqar, Yazan Kanaan. Project administration: Mohammad Al-Alawneh, Haitham Odat. Resources: Maulla Alali. Supervision: Mohammad Al-Alawneh. Writing—original draft: Mohammad Al-Alawneh, Ra’ed Al-Ashqar, Haitham Odat. Writing—review & editing: Yazan Kanaan, Maulla Alali. Approval of final manuscript: all authors.
Funding Statement
None
Acknowledgements
None