Successful Radiotherapy in Management of Inoperable Trichoblastic Carcinoma: A Case Report

Introduction

Trichoblastic carcinoma (TC) is a rare adnexal carcinoma (AC). Its clinical presentation is nonspecific and can simulate basal cell carcinoma (BCC) [1–3]. Optimal treatment and outcomes remains unclear: surgery with local excision remains the main standard treatment but there is no clear consensus on margins, which can lead to reconstructive dilemmas, especially for locally-advanced carcinomas [1,4]. Thus, conservative options must be developed as TC affects elder populations or inoperable tumors. Radiotherapy is widely used for cutaneous malignancies such as BCC or squamous cell carcinoma. These types of skin cancer are highly radiosensitive, and irradiation by radiotherapy or brachytherapy is an effective alternative to surgery in the case of advanced tumors [5,6], but its use in AC is poorly documented because of the rarity of this histology and its reputed radioresistance.

Case Report

An 86-year-old man was addressed to our Radiotherapy Department with a locally-advanced TC of the face. He was immunodeficient due to a kidney transplant and was treated with prednisone and tacrolimus. He denied a history of skin cancer or radiation therapy and there was not familial medical background of cutaneous malignancy. The lesion began on the nose and was asymptomatic, presenting as a slowly growing erythematous nodule. The first excision was performed in April 2020 by a general surgeon, with unknown margins. Histological examination was consistent with TC but excision was close to the surgical margins, requiring new excision.

However, for unknown reasons, surgery was not performed and recurrence was observed in August 2020, confirmed by biopsy. The patient was lost to follow-up for 4 months and was seen a plastic surgery department. Clinical examination revealed a 5-cm, growing tumor of the nose, extending to the right cheek and inner canthus, without visual impairment (Figure 1). A CT scan showed the lesion had invaded the medial canthus and the right orbit. There was not lymphadenopathy. Surgical excision or brachytherapy were not possible due to clinical extension, advanced age, and comorbidities.

After multidisciplinary discussion, it was decided to attempt external beam radiation with intensity modulated radiotherapy (IMRT) on tomotherapy. Seventy Gy was delivered in 35 fractions over 2 months 5/7 days (Figure 2). Bolus with ball (Seemed®) was used each treatment day to delivering an adequate dose of radiotherapy to the skin. Tolerance was characterized by grade 2 (NCI CTC AE V4) radiodermatitis, mucositis, and conjunctivitis managed by local medications (Figure 3).

Three months later, clinical examination did not reveal any residual lesion (Figure 4) and the adverse effects decreased. At 9 months, the patient remains tumor free clinically and MRI reveals reduction of the lesion (12×6 mm vs 41×22 mm) and an evolution towards a T2 hyposignal, which means that it is a scarring lesion rather than an active residual disease, suggesting the patient is being in complete remission, without dermatitis, conjunctivitis, or vision problems. There was only moderate grade 1 depigmentation (NCI CTC AE V4).

Discussion

We report a rare case of locally-advanced TC successfully treated by radiotherapy with 9 months of follow-up. Due to its rarity, guidelines for treating adnexal carcinomas are lacking, but surgical excision with 1–2 cm margins, or, if possible, Mohs micrographic surgery, remain the main treatments [4,7–9]. A literature review by Boettler et al found that 90.3% (n=84) of cases were treated by wide local excision. Margins ranged from 0.5 to 3 cm, with a median of 1 cm. Outcomes were reported for 40 cases, of which 87.5% (n=35) did not recur. Adjuvant treatment strategies such as radiotherapy or systemic therapy are not standardized due to the rarity of TC. Only 6 patients were treated by radiotherapy, and their outcomes were not reported [4].

Locally-advanced disease remains a therapeutic challenge, similar to BCC. Targeted therapies such as Vismodegib may help in locally-advanced or metastatic TC. Duplaine et al conducted a multicenter study of 16 cases. The overall response rate was 62.5%, including 2 complete responses and 8 partial responses, with median follow-up duration of 24 months [10].

Nevertheless, tolerance is the main issue, especially for older people. Radiotherapy is an alternative to surgery, with good efficacy and tolerance but it is poorly documented in AC.

For BCC, irradiation by radiotherapy or brachytherapy has similar results to surgery in terms of local control and may help cases that are inoperable because of their location or comorbidities, or for conservative treatment in the case of tumors located in functional areas (mainly peri-orifical) [5,6,11,12]. Similar to BCC, radiotherapy can be an alternative to surgery in AC, with good efficacy and tolerance, but it is poorly documented. Because of their rarity, only case reports or small series have been published. Yen et al published the results of 2 patients treated for eyelid AC, a location similar to our case, with 69 Gy and 59 Gy using irradiation techniques older than IMRT (2D photon radiotherapy and electron radiotherapy), with complete responses and no relapses. The toxicity of the treatment was not detailed, but the patients’ vision was preserved [13].

Stein et al published a case report of a nasal dorsal sebaceal carcinoma treated by external radiotherapy, without specifying the 58 Gy technique used. Tumor response was complete at 4 weeks, with moderate toxicity. Local recurrence was observed from the 6th month after treatment, necessitating radical surgery with total rhinectomy, with no recurrence at 12 months[14]. Adnexal carcinomas such as microcystic carcinoma and sebaceous carcinoma are known to be radioresistant, but this may not be the case for trichoblastic carcinoma (this needs to be confirmed by larger series).

For examples of TC treated with radiotherapy, a dose of more than 55 Gy may be necessary [13,14], as with our patient. Our patient had a good outcome in terms of tumor control and toxicity using a modern radiotherapy technique.

Conclusions

We report a rare case of locally-advanced TC, successfully treated by modern external beam radiation, which may be an acceptable alternative treatment for unresectable tumors.