Abstract
Sebaceoma is a rare benign cutaneous adnexal neoplasm with sebaceous differentiation that typically occurs in the head and neck region of elderly individuals. Sebaceoma extending into the external auditory canal is extremely uncommon. We report the case of an 85-year-old woman who presented with an enlarging mass involving the left tragus and extending into the external auditory canal. Histopathological examination demonstrated dermal nests of basaloid cells with sebaceous differentiation, and immunohistochemical analysis showed focal positivity for epithelial membrane antigen and Ber-EP4, leading to a diagnosis of sebaceoma. Complete excision and reconstruction with a full-thickness skin graft were performed. The postoperative course was uneventful, with complete graft survival, preservation of external auditory canal patency, and no evidence of recurrence at 6 months postoperatively. This case highlights the rarity of sebaceoma involving the external auditory canal and the importance of considering possible associations with Muir–Torre syndrome.
Introduction
Sebaceoma is a rare cutaneous adnexal neoplasm characterized by sebaceous differentiation and composed predominantly of basaloid cells. It typically occurs in the head and neck region of elderly patients and demonstrates a slow-growing, benign clinical course [1]. Sebaceoma extending into the external auditory canal is extremely rare, with only a few cases reported [1, 2]. Lesions involving the external auditory canal should be differentiated from malignant neoplasms such as basal cell carcinoma and sebaceous carcinoma, and reconstruction may be required following excision to prevent postoperative stenosis. Furthermore, sebaceous neoplasms, including sebaceoma, are recognized as cutaneous indicators of Muir–Torre syndrome (MTS), and therefore careful consideration should be given to their association with internal malignancies [1–4].
We report a rare case of sebaceoma extending into the external auditory canal, which was successfully treated with surgical excision and full-thickness skin grafting, resulting in favorable functional and aesthetic outcomes.
Case report
An 85-year-old woman presented with a mass on the left auricle, which she had initially observed ~15 years prior. The lesion had gradually enlarged, and she was referred to our department for further evaluation and treatment. On initial examination, a reddish elevated lesion ~2 cm in diameter was observed, extending from the left tragus to the entrance of the external auditory canal. The surface was rough without ulceration, discharge, bleeding, or canal obstruction (Fig. 1).
Initial clinical findings. A reddish elevated lesion extending from the left tragus into the external auditory canal without apparent canal obstruction.
The patient’s medical history included hypertension, lumbar spinal canal stenosis, gastroesophageal reflux disease, and chronic bronchitis. Her surgical history included total hysterectomy with bilateral salpingo-oophorectomy for uterine malignancy at the age of 83, as well as surgery for synchronous bilateral breast cancer. Her family history was notable for thyroid cancer in a younger sister.
An incisional biopsy was performed from the center of the lesion for diagnostic evaluation. Histopathological examination demonstrated dermal nests composed of basaloid cells without continuity with the overlying epidermis. Focal peripheral palisading was observed, and sebaceous differentiation was identified within the tumor nests. Mitotic figures were scarce, and retraction clefts surrounding the nests were not evident (Fig. 2A and B). Immunohistochemical examination demonstrated focal positivity for both epithelial membrane antigen (EMA) and Ber-EP4 (Fig. 2C and D). Considering the histopathological and immunohistochemical findings, the lesion was diagnosed as sebaceoma.
Histopathological and immunohistochemical findings. (A) Hematoxylin and eosin staining (×25) showing well-circumscribed dermal tumor nests composed predominantly of basaloid cells. (B) Hematoxylin and eosin staining (×400) demonstrating sebaceous differentiation with vacuolated cytoplasm and no significant atypia, prominent mitotic figures, or retraction clefts. (C) Immunohistochemical staining for EMA (×400) showing focal positivity. (D) Immunohistochemical staining for Ber-EP4 (×400) showing focal positivity.
The lesion was completely excised with circumferential dissection, including the portion extending into the external auditory canal (Fig. 3A and B). As the tumor base appeared adherent to adjacent external auditory canal cartilage, a portion of the cartilage was resected en bloc. Reconstruction was performed using a full-thickness skin graft measuring ~25 × 15 mm from the left groin. The graft was secured with 5–0 Vicryl, and antibiotic ointment-soaked cotton was placed in the external auditory canal as a bolster to prevent postoperative stenosis (Fig. 3C and D).
Intraoperative findings. (A, B) Tumor extension into the external auditory canal. (C) Preparation of a 25 × 15 mm full-thickness skin graft harvested from the left groin. (D) Reconstruction after complete tumor excision using a full-thickness skin graft.
The postoperative course was without complications, and the skin graft demonstrated full viability. At 6 months postoperatively, neither tumor recurrence nor stenosis of the external auditory canal was observed, and an acceptable anatomical contour was preserved (Fig. 4).
Postoperative findings at 6 months. No evidence of tumor recurrence or external auditory canal stenosis was observed, and favorable contour was maintained.
Discussion
Sebaceoma is a benign cutaneous adnexal neoplasm with sebaceous differentiation that typically occurs in the head and neck region of elderly patients and generally follows a slow-growing clinical course [1]. In the present case, the lesion had enlarged gradually over a period of ~15 years, which was consistent with previous reports.
Sebaceoma arising in the external auditory canal is extremely rare, and only a limited number of cases have been reported [1, 2].
Surgical excision is considered the preferred treatment for sebaceoma, and recurrence is considered uncommon when complete excision is achieved [1]. In the present case, the tumor extended into the external auditory canal. Because postoperative scar contracture may result in canal stenosis, reconstruction was required following tumor resection. Because the extent of canal resection was limited and collapse of the external auditory canal was considered unlikely, reconstruction was performed using a full-thickness skin graft alone. Kim et al. [2] also reported successful reconstruction with skin grafting after tumor excision, with no recurrence observed at 6 months postoperatively. The favorable postoperative course was consistent with previous reports.
In lesions involving the external auditory canal, differentiation from malignant neoplasms such as basal cell carcinoma and sebaceous carcinoma is particularly important. Histopathologically, sebaceoma is characterized by lobulated proliferation of basaloid cells with sebaceous differentiation. In contrast, basal cell carcinoma with sebaceous differentiation typically demonstrates peripheral palisading, retraction clefts surrounding tumor nests, and infiltrative growth patterns, all of which are important diagnostic features in the differential diagnosis [5].
Although focal peripheral palisading raised the possibility of basal cell carcinoma, the lesion showed well-circumscribed dermal nests with sebaceous differentiation and lacked significant atypia or infiltrative growth. Fan et al. [5] reported that immunohistochemical evaluation using EMA and Ber-EP4 is useful in differentiating sebaceoma from basal cell carcinoma. In the present case, both EMA and Ber-EP4 showed focal positivity. Taken together, these findings were considered consistent with sebaceoma.
Sebaceous neoplasms, including sebaceoma, are recognized as cutaneous manifestations of MTS. MTS is a variant of Lynch syndrome characterized by sebaceous neoplasms and internal malignancies. It is inherited in an autosomal dominant manner and is associated with DNA mismatch repair abnormalities [3]. Mismatch repair protein immunohistochemistry may help identify patients requiring further evaluation [4]. Fan et al. and Roberts et al. emphasized that comprehensive evaluation, including medical and family history in addition to histopathological findings, is important in patients with sebaceous neoplasms [4, 5].
In the present case, the patient had a history of uterine malignancy and synchronous bilateral breast cancer, raising the possibility of an association with a hereditary cancer syndrome, including MTS. No additional internal malignancies have been detected during follow-up. Analyses of mismatch repair protein expression and genetic testing were not performed; therefore, a definitive diagnosis of MTS could not be established. Sebaceous neoplasms should not be regarded solely as localized lesions, and further evaluation may be warranted when clinically indicated.
We report a rare case of sebaceoma extending into the external auditory canal that was successfully treated with surgical excision and full-thickness skin grafting. Favorable contour and external auditory canal patency were achieved, and the case highlights the importance of considering possible associations between sebaceous neoplasms and Muir–Torre syndrome.
Acknowledgements
The authors would like to thank Dr. Mayumi Inaba of the Department of Pathology, Yodogawa Christian Hospital, for her valuable assistance with the histopathological diagnosis and immunohistochemical evaluation of this case.
Conflicts of interest
The authors declare no conflict of interest.
Funding
The authors received no financial support for this work.
Consent
Written informed consent was obtained from the patient for publication of this case report and accompanying images.
