Australian Doctor 11th Oct Issue | Page 26

11 OCTOBER 2024 ausdoc . com . au inflammatory reactions , making it harder for patients to tolerate . 7

PHOTODYNAMIC THERAPY Photodynamic therapy ( PDT ) is primarily indicated for small , low-risk , superficial BCC or as adjuvant therapy post-surgical excision . 8 It combines photosensitising agents , such as 5-aminolevulinic acid lotion and methyl aminolevulinate cream , with light activation 2-3 hours later to selectively destroy tumour cells . This process is usually repeated one week later .

As with topical therapies , inform patients about the expected inflammatory reaction , including burning , stinging , pain , blistering , ulceration , erythema and local oedema , which usually peaks 3-4 days after the procedure .

The benefits of PDT include excellent cosmetic outcomes with minimal scarring . However , response rates for superficial BCC vary , with cure rates of 72-100 %. 9 , 10

RADIOTHERAPY Radiotherapy is an important option for patients unfit for surgery ( see figure 2 ), BCC in a difficult-to-treat location , or as an adjunct for extensive or recurrent BCC . Radiotherapy involves the delivery of ionising radiation to the target lesion in multiple fractions , which may occur over several weeks .

One of the main adverse effects of radiotherapy is an increased risk of new cutaneous malignancies , making it generally unsuitable for patients under 60 years of age and those with genetic conditions predisposing to skin cancer . 11 Other long-term risks include chronic radiation dermatitis , alopecia and poor cosmetic results in the form of hypo / hyperpigmentation , epidermal atrophy and telangiectasias . A randomised controlled trial quoted a four-year recurrence rate of primary facial BCC treated with radiotherapy as 7.5 % ( as compared to 0.7 % for surgery ). 12

MOHS MICROGRAPHIC SURGERY Mohs micrographic surgery ( MMS ), named after surgeon Frederic E Mohs in 1938 , is a specialised surgical method for skin cancer excision . Its most prominent benefits are that it that provides the highest cure rate and maximally preserves healthy non-cancerous tissue .

One Australian study with more than 3000 patients showed a five-year recurrence rate of 1.4 % in primary and 4 % in recurrent BCC . 13

MMS involves staged resection of the tumour , done under local anaesthesia and usually within a single day . With each stage , the tumour specimen is processed immediately by frozen section and the undersurface is examined microscopically . This technique allows for precise mapping of the remaining tumour , and the process is continued until there are no remaining tumour cells seen .

Cases most suitable for MMS include morphoeic , infiltrating and recurrent BCC , those with clinically ill-defined borders , and lesions in high-risk areas of the face , such as around the eyes , lips , ears and nose . 14

Table 1 . Clinical and histopathological features of different types of BCC

Nodular BCC ( see figure 1 )

Superficial BCC

Morphoeic BCC ( also called morpheaform , infiltrating or sclerosing BCC ; see figure 2 )

Pigmented BCC

Figure 1 . Biopsy-proven nodular BCC on the right tip of the nose in a middleaged woman . Different treatment options were discussed and the patient elected for Mohs micrographic surgery , given the higher rate of cure .

Clinical features

removal of the lesion and repair of the defect by side-to-side ( primary ) closure . Very large lesions or lesions on difficult areas of the face may require flap or skin graft repair . Generally , clinical margins of at least 3-5mm are recommended ( see table 2 ). If the lesion is incompletely excised , further surgery is recommended .

The five-year cure rate for surgical excision is reported as 95.2 %,

• Most common type of BCC on the face

• Translucent pearly papule or nodule

• Rolled edges

• Central depression , crusting or ulceration

• Blood vessels across its surface such as telangiectasia and arborising vessels on dermoscopy

• Most common type on the upper trunk or shoulders

• Well-circumscribed macule or patch , or thin papule or plaque

• Pale , pink or red in colour

• Slightly scaly

• Thin , translucent rolled edges

• White or yellow scar-like plaque

• Ill-defined borders

• Rarely ulcerates or bleeds

• Pigmented plaque or nodule

• Absent pigment network

• Multiple blue-grey globules or ovoid nests

• Structureless or leaf-like areas of pigment , especially in the periphery

• Blood vessels across its surface such as linear or arborising telangiectasia

• Spoke wheel areas with radial projections of pigment from a well-circumscribed dark centre

• Focal ulceration

although is much lower for lesions on the head . 16 A practical guide for surgical excision is outlined in box 1 .

BOWEN ’ S DISEASE

BOWEN ’ s disease , also known as intraepidermal SCC or SCC in situ , is a common superficial cancer of squamous cells confined to the epidermis . It is generally regarded as a premalignant dermatosis and , if left untreated ,

Histopathological features

• Discrete nests of basaloid cells

• Peripheral palisade of basaloid cells

• Slit-like stromal retraction

• Fibromyxoid stroma

• Basaloid cells parallel to the long axis of the epidermis

• Slit-like stromal retraction

• Thin columns of basaloid cells in a densely collagenised stroma

• Limited peripheral palisading

• Proplastic fibroblasts in the stroma

• Nodular or superficial BCC features but with pigmentation

• Colonisation of tumour islands with benign melanocytes

• Stromal melanophages

Table 2 . Recommended clinical margins for surgical excision of BCC and SCC , by risk group

Features

BCC

3-5 % may develop into invasive SCC . 19 Similar to BCC , UV radiation-induced DNA damage , along with mutations in tumour suppressor genes such as p53 , plays a crucial role in its pathogenesis . 20

Bowen ’ s disease primarily affects sun-exposed individuals aged over 60 , although it can occur at any age . Risk factors include fair skin ( Fitzpatrick types I and II ), sun exposure , arsenic exposure ,

Low risk High risk Low risk High risk

• Smaller than 10mm on the head and neck or smaller than 20mm elsewhere

• Nodular or superficial subtypes

• Well-defined borders

• No previous radiation therapy to the area

• Larger than 10mm on the head and neck or larger than 20mm elsewhere

• Aggressive types : morphoeic / infiltrating , basosquamous

• Poorly defined borders

• Immunocompromised patient

• Smaller than 10mm on the head and neck or smaller than 20mm elsewhere

• Well-differentiated and low grade

• Slowly growing

• No previous radiation to the area immunosuppression and a family history of skin cancer .

Additionally , human papillomavirus ( HPV ) infection , particularly types 16 and 18 , have been implicated in the development of Bowen ’ s disease , especially in genital lesions . 21

Bowen ’ s disease typically presents as well-demarcated , erythematous , scaly patches or plaques , most commonly on sun-exposed areas of the head , neck and extremities ( see figures 5 and 6 ). 20 It can also occur in other areas , such as inside the mouth , on the lips and in the genital area , where it usually presents as an ulcer or thickened scar . Lesions may be solitary or multiple and vary in size from a few millimetres to several centimetres .

Despite its premalignant nature , lesions are usually asymptomatic , thus causing a delay in seeking treatment . Occasionally , they may be mildly pruritic or tender .

Differential diagnoses

Differential diagnoses include seborrheic keratosis , actinic keratosis , BCC , melanoma , SCC and psoriasis . Dermoscopy findings suggestive of Bowen ’ s disease include a red , scaly plaque with irregular pigment network , white scales and coiled glomerular vessels . 22

Biopsy result

Bowen ’ s disease is usually diagnosed clinically ; however , histopathological examination ( after punch or shave biopsy ) remains the gold standard for confirmation of diagnosis .

Histological features include atypia of keratinocytes throughout the full thickness of the epidermis , without dermal invasion . 22

Dysplastic features of atypical keratinocytes include hyperchromasia , pleomorphism , increased mitotic activity and nuclear enlargement .

Treatment options

Similar to BCC , there are many available treatment options , with the selected approach considering the individual patient ’ s situation . As the risk of progression to invasive SCC is only 3-5 %, it may not be necessary to treat all lesions , particularly in elderly patients . 23

Topical formulations containing a keratolytic agent , such as urea or salicylic acid , can provide symptomatic relief by softening and exfoliating the affected areas .

SURGICAL EXCISION Surgical excision may be used for solitary lesions , especially those suspicious for invasive SCC ( see box 1 ). Table 2 outlines the surgical margins as a guide . A 2014 study showed that a hypothetical reduction of the clinical margin from 5mm to 4mm PAGE 29

SCC

• Larger than 10mm on the head and neck or larger than 20mm elsewhere

• Poorly differentiated tumour or aggressive grade

• More than 4mm in thickness

• Immunocompromised patient