Locally advanced basal cell carcinoma of the auricle and parotid region: A case report

Skin cancers are the most common malignant tumors in general. The most
 significant risk factor is exposure to UV radiation. They mainly occur in
 the head and neck region, and the majority of about 80% are basal cell
 carcinomas. Surgery is standard treatment of uncomplicated basal cell
 carcinomas, but a multidisciplinary approach is necessary in advanced cases.
 The case report refers to a patient with locally advanced recurrent basal
 cell carcinoma with primary tumor localization in the right auricle and
 parotid region in 2012 when primary surgery was performed. Due to the local
 recurrence, amputation of the right auricle and trepanation of the mastoid
 process was done in November 2018, and after that, radiation therapy of a
 recurrent tumor in the area of the trepanation cavity was applied. In the
 course of follow-up so far, there is good local control, without signs of
 toxicity. The case report points to the importance of a multidisciplinary
 approach and the role of radiotherapy in the treatment and control of
 advanced basal cell carcinoma of this region.


NTRODUCTION
Skin cancers have the highest incidence of all malignant tumors, and among them, the most common are basal cell carcinomas, about 80% of all skin cancers [1]. These cancers mainly occur in fair-skinned people, on parts of the body exposed to sunlight, such as the skin of the face, head and neck [2]. The most significant risk factor for the development of basal cell carcinoma is exposure to ultraviolet (UV) radiation.
The surgical approach is the most optimal way to treat these tumors. Depending on the local findings and stage of the disease, other modalities can be successful in treatment, such as electrodesiccation, curettage, cryotherapy, photodynamic therapy, topical application of 5-fluorouracil, or immunomodulators e.g. imiquimod, radiation therapy, or the use of the hedgehog inhibitor vismodegib [3,4].
In the case of forms of basal cell carcinoma that do not provide an adequate response to the applied treatment -"difficult to treat", such as locally advanced or recurrent tumors, it is necessary to refer the patient to a tumor board and consider multidisciplinary treatment [5].

CASE REPORT
A 72-year-old patient reported to the regional hospital, because of a tumor in size about 3 cm, of the right earlobe and parotid region in March 2012 when tumor resection and parotidectomy were performed. Histopathological findings showed basal cell carcinoma that infiltrated periglandular fibrous and adipose tissue as well as periauricular connective, adipose, and muscle tissue. In October of the same year, another excision was done, due to an infraauricular local recurrence with a diameter of 6 mm. Histopathological findings confirmed basal cell carcinoma, nodular type.
Local recurrence appeared again in 2018. The findings of computed tomography (CT) in November 2018, showed a tumor mass in the area of the rest of the right auricle measuring 30.7 × 22.2 mm that was growing into a mastoid process. Also, on CT examination, another tumor was seen in retromandibular area on the right, near the temporomandibular joint, size 14x13 mm, without infiltration of the mandible.
The surgery was performed in November 2018 when auricle amputation, mastoid process trepanation, and defect reconstruction were performed. Postoperative histopathological findings revealed basal cell carcinoma, a pathological stage of pT3, with multiple positive edges of resection.
Progression of the local finding was observed in March 2019. At that time, CT of the head and neck indicated suspicious infiltration of mastoid cells (Figure 1), and MR examination of the neck showed a tumor in the trepanation cavity of 23×21 mm. Radiological examinations did not show enlarged lymph nodes or other signs of disease dissemination.
The patient was presented to the tumor board for skin and soft tissue cancers, and it was suggested to continue treatment with radiation therapy. Before starting radiation therapy, the patient was referred to a dentist in order to prevent oral toxicity, and the patient was thoroughly acquainted with measures to prevent acute and chronic toxicity of radiation therapy.
Radiotherapy of local recurrence was planned by 3D conformal technique ( Figure 2) from three fields with TD 66 Gy in 33 fractions standard fractionation regime 2 Gy / day (Figures 3, 4). Radiation therapy was conducted in July 2019, with the development of local mucositis grade 2 of the buccal mucosa on the right and radiodermatitis grade 1 of the right buccal and surgically operated region.
The patient is now 80 years old and is regularly checked clinically and radiologically. Control MR examinations indicate stable disease and post-radiation fibrosis of the irradiated region. At the last control in March 2020, there were no signs of tumors and there was no toxicity of the treatment, without impairing the quality of life after the radiation therapy.

DISCUSSION
Basal cell carcinomas (BCCs) are the most common skin cancers. They arise from the basal layer of the epidermis or pluripotent basal cells of the adnexa and are usually found on hairy regions and parts that are most exposed to the sun.
There are several histological subtypes of BCC: nodular, superficial, pigmented, morphea, cystic, keratotic, and micronodular [6].   Clinical basal cell carcinomas have slow growth and are usually first seen as a small wound that does not heal spontaneously. Bleeding or pain occurs only when there is a significant increase in tumor size or involvement of adjacent structures. Basal cell carcinomas metastasize rarely but are characterized by infiltrative growth into the surroundings (dermis, fascia, periosteum, perichondrium, or nerve sheaths) [7].
The diagnosis of these tumors, especially lesions in the maxillofacial region, is usually not a problem due to easy visibility and availability of skin changes for biopsy or excision. However, there are some benign and malignant conditions and tumors that may mimic BCC in appearance, for example, trichoepithelioma, seborrheic hyperplasia, atypical fibroxanthomas, melanocyte nevi, Merkel cell carcinoma, and squamous cell carcinoma [7,8]. These diseases have different biological behavior, and in some cases extremely aggressive (Merkel cell carcinoma). Therefore, the definitive diagnosis is made only after a histopathological examination. Given that these cancers show infiltrative growth, recurrence and significant local destruction can occur if treatment is not carried out in proper time [6]. Surgery is the treatment of choice for uncomplicated cases, either as Mohs surgery or extensive excision, where achieving clean resection edges are curative.
Mohs micrographic surgery is a surgical technique by which the tumor is excised horizontally, layer by layer; sections are precisely mapped and immediately examined microscopically. The process is repeated so that the edges expand only on the positive margin until completely clean edges are obtained, while at the same time healthy tissue is spared. Therefore, it is necessary for the Mohs surgeon to be an educated dermatopathologist at the same time [9]. This method achieves the best results in the treatment of non-melanoma skin cancers, especially in regions where it is important to preserve function and/or cosmetic results, such as the maxillofacial region [10]. Cryosurgery in the treatment of skin cancer is limited to well-limited, low-risk superficial lesions that are smaller than 20 mm in diameter [11]. Curettage and electrodesiccation are also reserved for properly selected low-risk tumors [12]. The use of topical preparations of 5-fluorouracil or imiquimod is also successful only in superficial tumors [4,12]. In advanced cases, a multimodal approach should be considered.
The localization of basal cell carcinoma on the face can be a special aesthetic and functional problem. In elderly patients with localization of these tumors in the maxillofacial region, radiotherapy is recommended in the first line of treatment, which also achieves good cosmetic results. Also, advanced tumors often require the use of radiation therapy in an adjuvant or radical approach depending on the local stage [8,13].
Target therapy with hedgehog inhibitor oral drugs has been approved in advanced cases, in a neoadjuvant and systemic approach. Sonidegib is used only in locally advanced BCC, while Vismodegib can also be used in metastatic disease [12].
Locally advanced basal cell carcinomas are rare but can be challenging to treat because of their aggressiveness, especially with localization on the head and neck, or in the maxillofacial region. In such situations, the decision on treatment must be made in a multidisciplinary team that should consist of an ENT specialist, maxillofacial surgeon, radiation oncologist and sometimes other medical specialists.