Invading Basal Cell Carcinoma of the Bone: Diagnosis and Treatment Approaches

Abstract

Basal cell carcinoma (BCC) is the most common malignancy of skin but accounts for less than 1% of deaths caused by malignant disease. The majority of these carcinomas (85%) occur in the head and neck region. There are several predisposing factors for the development of BCC. These include light skin color, actinic exposure, and tissue injury caused by irradiation and chemical burns, together with some hereditary conditions such as xeroderma pigmentosa. BCC is a slowly growing and locally invasive epithelial neoplasm arising from the basal cell layer of the skin. Five clinical types of BCC exist: 1) nodulo-ulcerative BCC, including rodent ulcer; 2) pigmented BCC; 3) morphea-like or fibrosing BCC; 4) superficial BCC; and 5) fibroepithelioma. Nodulo-ulcerative BCC is the most common of these neoplasms. This type begins as a small waxy nodule, increases slowly in size, and often undergoes central ulceration. This represents the so-called rodent ulcer. Occasionally, BCC has an aggressive biological behavior, producing recurrences or/and metastasis. The anatomic location of the tumor seems related to the frequency of recurrences, with BCC of the sunlight-exposed areas recurring more frequently than BCC located in sunlightprotected areas. However, certain BCCs display a markedly aggressive pattern, with invasion and destruction of the underlying soft tissue and bone. Aggressive characteristics of BCC can be detected by histologic examination. However, in recent years there have been some findings of adjuvant markers that may be helpful in predicting the tumor behavior other than histologic findings. Some of the most widely used antibodies for this purpose are the cell proliferation markers. Among these markers, MIB-1 and proliferating cell nuclear antigen (PCNA) can be quantitatively evaluated with immunohistochemical staining. In the literature, only a few cases of invasion into the bones of the head and neck region have been reported. These include reports on involvement of skull, base of the skull, orbital bones, maxilla, and mandible. Herein we discuss 5 cases where the facial bones were involved by cutaneous BCC. We describe the clinical and histopathologic characteristics of the lesions. Diagnostic and treatment approaches of such cases are discussed.