Chapter V.4 Squamous Cell Carcinoma Including Actinic Keratosis, Bowen’s Disease, V.4 Keratoacanthoma, and Its Pigmented Variants Iris Zalaudek, Jason S. Giacomel, Bernd Leinweber Contents glected, squamous cell carcinoma may cause local tissue destruction and may metastasize [2, V.4.1 Definition . .295 3]. Moreover, after the diagnosis of an initial V.4.2 Clinical Features . .296 squamous cell carcinoma, the 3-year cumula- V.4.2.1 Invasive Squamous Cell Carcinoma. 296 tive risk for developing a second lesion is ap- V.4.2.2 Actinic Keratosis. .296 proximately 18% [4], emphasizing the need for V.4.2.3 Bowen’s Disease. 297 ongoing clinical surveillance. In its pathogene- V.4.2.4 Keratoacanthoma. .297 sis, chronic ultraviolet (UV) irradiation plays a major role, responsible for DNA mutations (usu- V.4.3 Dermoscopic Criteria. 297 ally in the p53 tumor suppressor gene) in trans- V.4.3.1 Squamous Cell Carcinoma. .297 formed epidermal keratinocytes [5]. This ex- V.4.3.2 Actinic Keratosis. .298 plains why squamous cell carcinoma typically V.4.3.3 Bowen’s Disease. 298 develops on chronic sun-exposed body sites V.4.3.4 Keratoacanthoma. .299 such as the face or forearms of fair-skinned in- V.4.4 Relevant Clinical Differential dividuals. Besides fair skin phototype, male Diagnosis. 299 gender, and age over 40 years, organ-transplant V.4.5 Histopathology. .299 recipients represent a major risk group for squa- V.4.5.1 Squamous Cell Carcinoma. .299 mous cell carcinoma, having up to a 65-fold in- V.4.5.2 Actinic Keratosis. .299 creased risk for development compared with the V.4.5.3 Bowen’s Disease. 300 general population [6]. In this particular patient V.4.5.4 Keratoacanthoma. .300 group, 22% of squamous cell carcinomas will develop on sun-protected body sites such as the V.4.6 Management. .300 trunk or lower extremities. V.4.6.1 Squamous Cell Carcinoma. .300 So-called precursor lesions of squamous cell V.4.6.2 Actinic Keratosis. .300 carcinomas include actinic keratosis, Bowen’s V.4.6.3 Bowen’s Disease. 301 disease, and erythroplasia of Queyrat, although V.4.6.4 Keratoacanthoma. .301 a common etiological background is questioned, References. .301 based on differences in clinical, histopathologi- cal, and pathogenic profile. However, since these lesions are all epidermal neoplasias with a cer- tain potential of malignant progression, they V.4.1 Definition are commonly grouped within the spectrum of squamous cell carcinoma [7]. Invasive squamous cell carcinoma is the second Actinic keratoses are considered to be the most common skin cancer after basal cell carci- earliest form of squamous cell carcinoma, with noma and causes the majority of deaths among the risk of an individual lesion progressing to the non-melanoma skin malignancies. When invasive squamous cell carcinoma reported to detected and treated early squamous cell carci- vary from 0.1% up to a considerable 20% [8, 9]. noma has a 95% cure rate [1]; however, if ne- Nevertheless, even with a low individual rate of 296 I. Zalaudek, J.S. Giacomel, B. Leinweber progression, patients with multiple actinic kera- toses (i.e., more than 10) may have a 14% cumu- lative probability of developing squamous cell carcinoma, either within the actinic keratosis or de novo, within 5 years. This underscores the need for regular follow-up in these patients [8]. Bowen’s disease is a peculiar variant of squa- mous cell carcinoma in situ that frequently oc- curs in locations not exposed to solar irradia- tion. Consequently, some controversy exists regarding a common etiological background of Bowen’s disease and squamous cell carcinoma. Bowen’s disease differs significantly from ac- tinic keratosis and squamous cell carcinoma in Fig. V.4.1. Clinically, this invasive squamous cell car- its clinical and histopathological features as well cinoma presented as a pigmented and keratotic nodule in its pathogenesis, which is related to human located on the ear (antihelix) of a 78-year-old woman. papilloma virus infection, prior arsenic expo- Clinical differential diagnoses included of basal cell car- sure, radiation therapy, and internal malignan- cinoma, nodular–verrucous melanoma, and seborrheic keratosis. However, the lesion also had a history of recent cies, in addition to chronic UV exposure. In change, which increased the index of suspicion for ma- contrast, chronic UV irradiation is the primary lignancy and led to a punch biopsy of the lesion. Histo- carcinogen associated with actinic keratosis and pathology revealed a pigmented invasive a squamous cell squamous cell carcinoma [10, 11]. If left untreat- carcinoma and the lesion was subsequently excised ed for a variable period of time, Bowen’s disease may progress to a variant of invasive squamous cell carcinoma known Bowenoid carcinoma, in V.4.2.1 Invasive Squamous Cell 3–20% of cases [12, 13]. Remarkably, Bowenoid Carcinoma carcinoma may metastasize in up to one-third of cases, thus conferring a relatively poor prog- nosis[12]. Invasive squamous cell carcinoma typically oc- In further contrast, keratoacanthoma is also curs along with the presence of multiple actinic often cited as a “self-healing” variant of squa- keratoses. The initial, in-situ lesion is character- mous cell carcinoma, because it typically shows ized by a reddish, ill-defined plaque that may be a self-limiting course. Therefore, there is some difficult to distinguish from hyperkeratotic ac- question as to whether keratoacanthoma is a tinic keratosis. If left untreated, squamous cell true malignancy, or should be best regarded it as carcinoma in situ may progresses to invasive a benign “pseudocarcinoma” [14–16]. However, squamous cell carcinoma, which typically ap- reports which describe local tissue destruction pears as a firm, infiltrating, and often ulcerated and metastasis keratoacanthoma have led to a nodule, which enlarges fairly rapidly over a consideration of this tumor as a variant of squa- number of week or months. In addition, pig- mous cell carcinoma [17, 18]. Consequently bi- mented invasive squamous cell carcinoma may opsy and definitive treatment of keratoacantho- presents as a blue-to-black nodule with a scaly ma is generally recommended. surface (Fig. V.4.1). V.4 V.4.2 Clinical Features V.4.2.2 Actinic Keratosis Although the majority of these epidermal tu- Actinic keratoses appear as multiple macules, mors are usually non-pigmented, pigmented papules, or plaques surmounted by an adherent variants may also occur. surface scale, with some degree of erythema ranging from pale pink to dark red. Sometimes SCC and variants Chapter V.4 297 Fig. V.4.2. This pigmented actinic keratosis located on Fig. V.4.3. Keratoacanthoma typically develops rapidly the cheek of a 65-year-old man was clinically difficult to and presents clinically as a dome-shaped nodule with a distinguish from solar lentigo and lentigo maligna, espe- central plug of keratin, as seen in this image cially since it is a solitary pigmented macule lacking the typical surface scales or the neighboring sign with other lesions V.4.2.4 Keratoacanthoma actinic keratoses reveal a hyperkeratotic surface with crusts or erosions and may cause sensa- The clinical course of keratoacanthoma is typi- tions of burning or itching. Pigmented actinic fied by a rapid enlargement within a few weeks keratoses are less frequent but occur as light- to until a stabilization of growth is reached. After dark-brown irregular plaques or macules, usu- a variable time, a spontaneous involution results ally with a scaly surface. Pigmented actinic ker- in the regression of the lesion. The typical ap- atoses may clinically mimic solar lentigo, sebor- pearance of keratoacanthoma is that of a dome- rheic keratoses, pigmented Bowen’s disease, or shaped nodule of variable size characterized by lentigo maligna (Fig. V.4.2). a central crater filled with a mass of keratin. The diameter of a common solitary keratoacantho- ma can range from a few millimeters up to a V.4.2.3 Bowen’s Disease considerable 3 cm. Multiple lesions can occur spontaneously in the Gryzbowski variant, or in The clinical appearance of classical non-pig- Muir–Torre syndrome (Fig. V.4.3) [19–21]. mented Bowen’s disease is represented by a slowly growing, erythematous, well-demarcated plaque with a scaly or crusted surface that may V.4.3 Dermoscopic Criteria be eroded. Clinical differential diagnoses in- clude a variety of non-pigmented skin tumors V.4.3.1 Squamous Cell Carcinoma or erythemato-squamous skin disorders, such as actinic keratosis, basal cell carcinoma, amel- Dermoscopically, non-pigmented invasive squa- anotic melanoma, clear cell acanthoma, psoria- mous cell carcinoma frequently exhibits linear- sis, viral warts, and eczema, to name but a few. irregular, hairpin, or dotted vessels, or combina- In contrast, pigmented Bowen’s disease is less tions thereof (the so-called polymorphous or common and presents clinically as a non-uni- atypical vascular pattern) [22]. Typically, these formly pigmented plaque with a scaly or verru- vessels are surrounded by a whitish halo, which cous surface which should be differentiated is a dermoscopic hallmark of all keratinizing tu- from seborrheic keratosis, pigmented actinic mors. Ulceration and blood crusts, if present, ap- keratosis, solar lentigo, basal cell carcinoma, pear as irregularly distributed reddish to brown- blue nevus, melanocytic nevi, and melanoma. ish to black blotches on the surface of the tumor. 298 I. Zalaudek, J.S. Giacomel, B. Leinweber Fig. V.4.4. Dermoscopy of the pigmented invasive squa- Fig. V.4.5. Dermoscopy of the pigmented actinic kerato- mous cell carcinoma, as shown in Fig. V.4.1. reveals sur- sis depicted in Fig. V.4.2 reveals the same features as len- face scale, a blue-white veil and irregular brown-to-black tigo maligna, characterized by rhomboidal structures and blotches.