Key points

Introduction

Cutaneous malignancy represents a worldwide public health problem, with a rapidly rising incidence, decreasing age at presentation, and significant health care costs. Head and neck skin cancers encompass a broad range of histologies, the most commonly encountered entities being basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma. Many health care providers diagnose and treat skin cancer, from providers at rural primary care clinics to those at urban dermatologic surgery practices and large tertiary care head and neck cancer centers. Some of these tumors prove to be diagnostic and treatment challenges, with associated increased morbidity and mortality.

Most cutaneous malignancies, BCCs, and SCCs can effectively be treated through a variety of means when diagnosed early enough. Some NMSCs and melanoma spread to regional lymph nodes, can be aggressive, and recur locally. Aggressive and more advanced lesions demand multimodality treatment entailing surgical resection, staging of the regional lymph node basins, and radiation therapy, as the survival from aggressive disease remains poor because of locoregional recurrences and distant metastasis. Potentially advanced and aggressive tumors merit more comprehensive evaluation and treatment by a multidisciplinary team of experts in cutaneous oncology. This article reviews the management of skin cancer of the head and neck, including BCC, SCC, and melanoma.

Introduction

Cutaneous malignancy represents a worldwide public health problem, with a rapidly rising incidence, decreasing age at presentation, and significant health care costs. Head and neck skin cancers encompass a broad range of histologies, the most commonly encountered entities being basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma. Many health care providers diagnose and treat skin cancer, from providers at rural primary care clinics to those at urban dermatologic surgery practices and large tertiary care head and neck cancer centers. Some of these tumors prove to be diagnostic and treatment challenges, with associated increased morbidity and mortality.

Most cutaneous malignancies, BCCs, and SCCs can effectively be treated through a variety of means when diagnosed early enough. Some NMSCs and melanoma spread to regional lymph nodes, can be aggressive, and recur locally. Aggressive and more advanced lesions demand multimodality treatment entailing surgical resection, staging of the regional lymph node basins, and radiation therapy, as the survival from aggressive disease remains poor because of locoregional recurrences and distant metastasis. Potentially advanced and aggressive tumors merit more comprehensive evaluation and treatment by a multidisciplinary team of experts in cutaneous oncology. This article reviews the management of skin cancer of the head and neck, including BCC, SCC, and melanoma.

Epidemiology

Cutaneous BCC and SCC are the most commonly diagnosed NMSCs in the United States and account for over 1 million new cancers annually. Approximately 70% to 80% of all skin malignancies are BCCs, whereas 15% are SCCs. The remaining 5% are primarily melanoma and other uncommon entities, particularly adnexal tumors and Merkel cell carcinomas. The clinical behavior of BCC is distinct from that of SCC. BCC is locally aggressive with a low propensity for metastasis; SCC may display aggressive biological behavior, characterized by perineural invasion and potential for regional metastasis.

Although melanoma represents less than 5% of the cases, it is responsible for more than 75% of skin-cancer-related deaths. In the United States, each year about 70,200 patients are diagnosed with melanoma and 8800 die of this disease. The incidence of melanoma has risen dramatically over the past several decades, with an increase of greater than 200% in the age-adjusted incidence from 1975 to 2008. This increase is manifested across all age groups and primary tumor thicknesses. The mortality rate has also increased approximately 60% over time, primarily because of increased mortality in patients aged 65 years or older, particularly among men. However, many patients who die of melanoma are young and healthy, so melanoma is among the cancers with the highest life years lost per fatality.

Risk factors

Sun exposure is the single greatest risk factor for the development of NMSC. Both the duration and intensity of UV radiation (UVR) exposure, primarily UV-A (320–400 nm) and UV-B (290–320 nm) radiations, contribute to DNA damage at the cellular level of the epidermis. Thus, these cancers usually arise in sun-exposed areas and progress from premalignant actinic lesions to invasive carcinomas. Similarly, individuals with a history of facial or neck irradiation are at an increased risk for the development of skin cancer.

For melanoma, there is also strong evidence that increased exposure to UVR plays a role. Multiple studies support a causative role for UVR in cutaneous melanoma. A history of sunburns from natural UVR and the use of tanning beds (artificial UVR) are risk factors for melanoma. Public surveys have reported increasing prevalence of both behaviors among US adults. Intermittent sun damage/exposure has consistently been identified as a risk factor, whereas some studies suggest that long-term sun exposure is associated with a decrease in the risk of melanoma. Other risk factors for cutaneous melanoma include a family history of the disease, multiple nevi, dysplastic nevi, freckled or fair skin, blue or green eyes, and red hair.

It is increasingly recognized that patients who have undergone organ transplant have a 30-fold increased risk of developing cutaneous SCC and 10-fold increased risk of developing BCC. The role of the human papillomavirus in skin carcinogenesis is under investigation. Other than sun avoidance and the use of topical sunblock with a sun protection factor exceeding 30, no preventative treatments are available.

Nonmelanoma skin cancer

Clinical Evaluation

A complete history and physical examination is paramount in the accurate assessment of the patient with NMSC. An enlarging or ulcerating skin lesion should be deemed to be a skin cancer until proven otherwise and should prompt immediate dermatologic attention for biopsy. Patients commonly report a remote history of a previously resected cutaneous malignancy, which may explain new-onset neck adenopathy, facial paresthesias, or a facial nerve paralysis. Complaints that suggest perineural invasion include facial weakness, formication (the sensation of insects crawling on the skin), hypesthesia, dysesthesia, and paresthesia. A recurrent lesion may present as a slow-growing subcutaneous mass that invades the deep facial or neck musculature.

A complete dermatologic examination is necessary for the patient with NMSC. Numerous premalignant lesions may be present, and judicious biopsies should be performed. The clinician should pay particular attention to the identification of second primary tumors. The dimensions of the primary tumor and its involvement with adjacent structures must be assessed. In the temporal and scalp regions, the cranial periosteum is a reliable barrier to bony invasion, which can be determined by the mobility of the lesion over the underlying deep tissue planes. Preauricular tumors may extend into the parotid gland or the external auditory canal, whereas cancers of the midface may extend along embryonic fusion planes to the nasal cavity or orbit. Other problematic areas are the nasolabial fold, the glabella, and the postauricular crease.

The clinician should have a high index of suspicion for perineural invasion in the patient with SCC, and a thorough evaluation of the sensory and motor nerves may elicit objective evidence of nerve invasion. This evidence can sometimes be obtained through preoperative imaging such as computed tomography (CT) or MRI.

BCC rarely spreads to the cervical lymphatics, whereas regional spread is common in patients with SCC. Overall, 25% of patients with advanced SCC ultimately develop parotid or neck metastases. Lesions of the face and scalp that are anterior to an imaginary line drawn through the external auditory canal in the coronal plane frequently metastasize to the parotid bed. The posterior triangle and nuchal lymphatics may be involved by cutaneous lesions posterior to the anatomic plane, whereas submental and submandibular metastases arise from midface and lower lip lesions.

High-resolution axial and coronal imaging is necessary for the complete staging of disease in the patient with NMSC. CT is generally preferred over MRI for evaluating the primary tumor, the status of the lymph nodes, and the presence of bony invasion. MRI is better for the detection of perineural spread, dural invasion, and orbital disease ( Fig. 1 ). Patients with bulky lymph node metastasis should also be evaluated for distant metastasis with a CT scan of the chest. Ultrasonography of the neck and parotid bed is effective for the evaluation of the regional lymphatic basins. This technique can be combined with a fine-needle aspiration for the pathologic confirmation of neck node metastasis. The role of fludeoxyglucose PET has not been fully elucidated, but this modality may have a role in the detection of deep soft tissue disease recurrence or distant metastasis in the previously treated patient.

Perineural spread. Coronal section of a contrast-enhanced CT scan of the head and neck depicting perineural spread along the right inferior orbital nerve. Note the abnormal thickening of the nerve within the infraorbital canal ( arrow ).

Histologic confirmation of all lesions is necessary in the treatment of NMSC because they may harbor aggressive pathologic features such as perineural or lymphovascular spread.

Pathology

Most NMSCs are BCCs, which arise from the basal layer of the cutaneous epithelium ( Fig. 2 ). The 3 most common histologic subtypes of BCC, ranging from least to most aggressive, are (1) nodular, (2) superficial multifocal, and (3) infiltrative. The nodular subtype accounts for 75% of all BCCs and is characterized by a raised, pearly lesion that is well circumscribed. The superficial subtype (10%) presents as an erythematous scaly plaque. The aggressive or infiltrative BCC (previously referred to as morpheaform BCC) has a propensity for subcutaneous invasion with fingerlike projections of tumor that extend into the surrounding soft tissues. Clinically, the lesion appears as a raised yellow plaque with indistinct borders. Other less common histopathologic subtypes include basosquamous carcinoma and pigmented BCC.

Epidermal anatomy. Epidermis is the outermost layer of the skin and contains 5 specialized layers.

SCC accounts for 15% all skin cancers and is thought to arise from the spinous layer of the skin epithelium (see Fig. 2 ). Clinically, SCCs are ulcerative lesions that may arise in an actinic keratosis, a previous scar, or sun-exposed areas. Squamous variants include adenosquamous carcinoma, spindle cell carcinoma, and clear cell tumors. In some cases, immunohistochemistry is necessary to establish the exact pathologic diagnosis. These tumors display aggressive histopathologic behavior, with perineural invasion present in more than 15% of patients. Lymphovascular invasion is also common, with metastases to cervical lymphatics in 5% to 10% of patients. As expected, patients with SCC are at higher risk for distant metastasis and adverse prognosis than are those with BCC.

Treatment

Surgery

Primary tumor

Surgical resection is the mainstay of treatment of NMSC. A variety of surgical options are available for local treatment of lesions that are smaller than 1 cm. Electrodessication or cryotherapy should not be used, because margin analysis is not possible. Wide local excision and Mohs surgery are equally effective and offer at least 95% cure rate with minimal morbidity. Margins of 0.5 cm are usually sufficient for 1-cm lesions. Tumors that are larger than 1 cm in greatest dimension should be resected with 1-cm margins circumferentially. In every case margin assessment is critical to ensure complete tumor removal.

Larger lesions that are deeply invasive require a more generous surgical margin of at least 1 to 2 cm, which may necessitate a complex reconstruction. The deep and lateral margins of the tumor must be cleared histopathologically at the time of resection, particularly when immediate reconstruction is contemplated. Frozen section analysis of the adjacent tissue margins is mandatory before reconstruction is undertaken. Close cooperation between the surgeon and the pathologist is necessary to permit intraoperative assessment of all critical margins. The extent of surgical resection is dictated by the clinical and radiographic evaluation, and the patient should be prepared for bony, cartilaginous, neural, or soft tissue resection. For tumors arising on the ear or preauricular skin, deep invasion may require parotidectomy to clear the tumor margins and safely preserve the facial nerve. For tumors fixed to or invading the skull, preoperative consultation with a neurosurgeon is necessary if the resection requires a craniectomy. Surgical resection and reconstruction of the eyelids typically requires input from an experienced oculoplastic surgeon.

Large (>4 cm) deeply invasive BCCs and SCCs are best treated with resection and histologic confirmation of margin clearance. These tumors may require parotidectomy with or without preservation of the facial nerve, amputation of the auricle, and even maxillectomy or mandibulectomy. Antegrade and retrograde resection of the facial or trigeminal nerves requires oncologic surgical experience to ensure complete tumor removal. Mohs surgery has a clear role in the following scenarios: (1) tumors extending along embryonic fusion planes, (2) lesions of the eyelid or periorbital region, (3) localized BCC and SCC, and (4) when maximum tissue conservation is important. The long-term results after Mohs surgery for these lesions are favorable, although close surveillance for the development of recurrence is necessary.

Regional nodes

As less than 1% of all BCC metastasize, regional progression is generally not an issue in this disease. SCC, however, has an overall 5% rate of spread to the neck. The following risk factors have been identified that portend lymphatic metastasis: (1) tumor size greater than 5 cm (2) perineural invasion, and (3) deep soft tissue invasion. Elective dissection of the neck is generally not indicated, except when parotid metastases are identified. Most patients with these aggressive lesions require postoperative radiation, and thus the neck may be included in the radiation fields for elective neck treatment. When clinical or radiographic metastases are evident, a therapeutic neck dissection is warranted.

The type of neck dissection performed is predicated on the location and extent of metastasis. The parotid gland is the lymphatic watershed for cutaneous malignancies arising on the ear, anterior scalp, forehead, upper and lower eyelid, and preauricular skin. Efferent lymphatics from the parotid drain to the upper jugular lymph nodes and the superficial lymph node that lies adjacent to the upper external jugular vein. When a parotid metastasis is due to a tumor in one of the locations described, coexistent metastasis to the upper cervical nodes is present in 20% to 30% of patients. The appropriate lymphadenectomy would include parotidectomy and dissection of the lymph nodes in levels I–IV. Nodes in level V should be dissected if clinically involved or if lesion arises in a postauricular location. In most instances, a neck dissection can be performed while sparing nonlymphatic structures such as the sternocleidomastoid muscle, internal jugular vein, and the spinal accessory nerve.

Radiotherapy

Primary tumor

Primary radiation for BCC and SCC is primarily reserved for patients who are not surgical candidates. Other clinical situations in which primary radiation therapy may be considered are lesions that involve cosmetically or functionally important anatomic regions, such as the eyelid or the lip.

Adjuvant radiation

External beam radiotherapy is used as a postsurgical adjuvant for patients with high-risk NMSC ( Box 1 ). In a few patients who have marginally resectable tumors involving the face or neck, preoperative radiotherapy can be used to decrease the tumor size and permit resection. However, an operation followed by postoperative radiation therapy (PORT) is preferred for patients with recurrent tumors, perineural invasion, lymph node metastasis, extracapsular lymph node disease, positive margins, deep soft tissue or bony invasion, tumors larger than 4 cm, and unfavorable or aggressive histologies. Treatment decisions in this regard should be made in the context of a multidisciplinary team.

Box 1

• 
  

  Perineural invasion

  
  
• 
  

  Lymphatic or parotid metastasis

  
  
• 
  

  Recurrent lesions

  
  
• 
  

  Bone invasion

  
  
• 
  

  Extracapsular spread

  
  
• 
  

  Unfavorable histologies

  
  
• 
  

  Large tumors (>4 cm)

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