Abstract
Radiation therapy to the head and neck for the treatment of benign diseases carries the potential for the late development of carcinoma. Low-dose radiation has been used as an adjunctive treatment for recurrent keloids, especially massive keloids, but the carcinogenic potential of ionizing radiation in this setting remains controversial. We report the case of a 37-year-old black woman with a history of severe earlobe keloids who had been first treated with resection and postoperative radiation at the age of 9 years. When she had reached the age of 36 years, she required reoperation for massive keloid scarring after which she underwent a second course of postoperative radiation to the right side of her face and neck. Some 20 months after the second administration of radiation therapy, she developed a mucoepidermoid carcinoma in the right parotid gland. The tumor was successfully treated with surgery.
Introduction
Radiation therapy was first used in 1906 as an adjunctive treatment for malignancies. Since then, epidemiologic studies have demonstrated that ionizing radiation carries a potential risk for carcinogenesis.13 We report the case of a woman who developed recurrent severe earlobe keloids 27 years after she had undergone surgery and radiation therapy for the same condition as a child. Following the second administration of radiation therapy, she developed a mucoepidermoid carcinoma (MEC) of the parotid gland.
Case Report
A 37-year-old black woman presented to us for evaluation of a mass beneath the angle of the right mandible. She had a history of repeated administrations of radiation therapy. When she was 9 years old, she developed bilateral keloids after having her ears pierced. The keloids were surgically removed from both ears, and postoperative low-dose radiation (60 Gy) was administered to the ears and to portions of the right side of her face.
At the age of 18 years, the patient developed significant acne over her face, chest, and back. By the age of 36 years, she had developed a massive keloid formation and fibromatosis across her face, which essentially replaced her ear and extended along her jaw anteriorly (figure 1). Some 20 months before her presentation to us, she underwent multiple keloid excisions, each of which was followed by administration of low-dose (80 Gy) radiation therapy to the right side of the head and neck.
Before the patient's second round of surgery and postoperative radiation therapy, the keloids are seen replacing the right ear and extending along the jaw anteriorly.
As part of our examination, we obtained a fine-needle aspiration biopsy, which identified hyaline fibromatosis with atypical epithelial cells suggestive of an MEC. Computed tomography (CT) of the head, neck, and chest identified a mass roughly 10 cm wide beneath the keloid (figure 2). The mass extended medially into the neck, where it had medially displaced the tongue and pharynx. The right jugular vein was occluded, and the mass had displaced the carotid artery.
CT shows the 10-cm mass (arrow) beneath the keloid. The mass has displaced the tongue, pharynx, and carotid artery medially. The right jugular vein is occluded.
In view of the size of the mass, preoperative radiation therapy was performed. The patient then underwent a right suprahyoid neck dissection with a parotidectomy. Intraoperatively, gross involvement of the right facial nerve was seen, and it was therefore sacrificed. A rotational flap was created to close the wound.
Histopathologic examination identified the mass as an intermediate-grade MEC. Some tumor was present at the resection margins, but the patient refused further surgery. At 2 years of follow-up, she exhibited no evidence of recurrence.
Discussion
Keloids are benign dermal tumors that form during an abnormal wound-healing process in genetically susceptible individuals. They are defined as a healed skin wound that extends beyond the confines of the original wound, and they are characterized by overabundant collagen deposition.4,5 Keloids occur in all races, but there is a predisposition for patients with dark-pigmented skin; the two sexes are equally affected when age-matched criteria are used. 4 The disease has a familial component, although the mode of inheritance is unclear. 6 In our patient, the initial keloid lesions had been caused by ear piercings, but the development of acne later in life led to the massive keloid formation.
Keloids represent the most extreme example of cutaneous scarring and the most difficult to treat. 5 Surgical resection alone is associated with reported recurrence rates ranging from 45 to 100%.3–5 On the other hand, one study found a 1-year recurrence of only 12.5% after surgical resection followed by radiation therapy. 7 While there is currently no agreement on the optimal radiation dosage, fractionation, or timing with respect to surgical procedures, radiation therapy is still considered an appropriate adjuvant therapy.
Clinicians often hesitate to recommend radiation therapy because of the potential risk of radiation-induced malignancy.1–3 In our case, the sheer mass of the keloids necessitated the use of extensive radiation after the keloids had been debulked. After two courses of radiation therapy, the patient developed a parotid gland MEC.
In a review of cases from 1940 to 1994, investigators at the Mayo Clinic identified 89 parotid gland MECs; in 10 of these cases (11.2%), the patients had been exposed to ionizing radiation. 8 Other studies have also implicated exposure to ionizing radiation as the causative factor in MEC; for example, some 44% of patients who underwent radiation therapy for salivary gland tumors developed an MEC.9,10
MEC accounts for less than 10% of all salivary gland tumors, but the risk of malignancy is increased by (1) exposure to radiation at a young age, (2) female sex, and (3) a high radiation dosage.1,8
In a review of 2,945 children who received minimal radiation to reduce the size of their tonsils, Schneider et al found that 91 salivary gland neoplasms (3.1%) occurred during follow-up, with the parotid gland being the most common site and MEC the most common malignancy. 9 This finding indicates an association between salivary gland tumors and irradiation. It is possible that the use of repeated radiation therapy as an adjunct in the treatment of keloids, as occurred in our patient, may further increase the risk of a salivary gland malignancy, but this has not been proven.
MECs are classified histologically into three grades: low, intermediate, and high. The grade is based on the relative proportion of cell types. Our patient was found to have an intermediate-grade MEC, which is less cystic than a high-grade tumor and has a greater tendency to form large, irregular nests or sheets of squamous cells that often have a prominent intermediate-cell population. 11 The prognosis is a function of the histologic grade, the adequacy of excision, and clinical staging.
Complete surgical excision is the treatment of choice. Adequate excision is important for all grades of tumor, as significantly higher recurrence rates occur with positive surgical margins. Postoperative radiation therapy is indicated for patients with histologically proven positive margins or high-grade tumors.10,11
In conclusion, irradiation is recognized as an appropriate adjuvant therapy to prevent keloid recurrence, but patients so treated require long-term surveillance to monitor for the development of a malignancy in the treatment area. Patients who require repeated adjunctive radiation therapy to the same area may be at an even higher risk of developing a malignancy, but this remains to be proven.