IV.10.1 Definition
Scalp melanoma is defined as melanoma that occurs on the usually hair-bearing area of the head, although it is commonly included within the group of head/neck melanomas. Scalp mela- noma has been referred to as an “invisible kill- er”, because of its poorer prognosis compared with melanoma on other body sites [1–4]. Re- markably, if the head and neck region is subdi- vided into non-hair-bearing and hair-bearing areas, significant differences in distribution of the various melanoma subtypes, as well as in sex and prognosis, can be found; thus, lentigo ma- ligna and lentigo maligna melanoma is the most common type, occurring on facial skin of el- derly females, whereas superficial spreading melanoma and nodular melanoma are predom- inantly found on the scalp and ear in males over the age of 50 years [2, 5–7].
Scalp Melanoma
Iris Zalaudek, Jason S. Giacomel, Bernd Leinweber IV.10
Contents
IV.10.1 Definition . . . .265
IV.10.2 Clinical Features . . . .265
IV.10.3 Dermoscopic Criteria . . . .266
IV.10.4 Relevant Clinical Differential Diagnosis . . . .267
IV.10.5 Histopathology . . . .267
IV.10.6 Management . . . .267
IV.10.7 Case Study . . . .267
References . . . .268
Interestingly, the overall 5-year survival rate of melanoma of the head decreases according to its location from 86% in non-hair-bearing areas to 47% in usually hair-bearing areas [7, 8]. Fur- thermore, malignant blue nevus, a rare variant of melanoma, has a significant predilection for the scalp and may arise in a pre-existing blue nevus of the cellular type [9–11].
Of further interest, the proportion of scalp melanoma compared with other locations is re- ported to be higher in children than in adults.
Again, also in this age group, scalp melanoma is characterized by a poorer prognosis compared with the other body sites [12–14].
A possible explanation for the poor prognosis of scalp melanoma might be related to a delayed detection, since the skin is often covered by hair and therefore not easily accessible to clinical ex- amination.
IV.10.2 Clinical Features
Based on the epidemiological data, scalp mela- noma reveals typically two main clinical faces:
one of superficial spreading melanoma, and the other of nodular melanoma (including the vari- ant of malignant blue nevus).
Superficial spreading melanoma grows hori-
zontally in its in-situ form and, after a variable
time span, changes its growth into the vertical
phase and thus becomes invasive. The clinical
characteristics are summarized in the clinical
ABCDE rule. The letters represent the typical
features of superficial melanoma, such as asym-
metry (A) in shape, irregular borders (B), color
variegation (C) from white to brown to black or
blue, a diameter more than 6 mm (D) or larger,
and an evolution (E) over time. When left un-
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treated, superficial melanoma becomes nodular and may additionally reveal ulceration. Superfi- cial scalp melanoma may reach a considerable size involving large areas of the scalp, which might be related to a delayed detection since the skin is often covered by hair and therefore not easily accessible to the clinical examination (Fig. IV.10.1).
In contrast to superficial melanoma, nodular melanoma, and malignant blue nevus, lack most of the features summarized in the clinical ABCD rule, since both commonly appear as only slightly asymmetric, often well-defined, blue- to-black nodule of variable diameter. The E cri- terion seems to be the most important criterion in the diagnosis of nodular melanoma and ma- lignant blue nevus, since both are characterized by a rapid and aggressive invasive vertical growth. Unfortunately, the first clinical symp- toms, such as ulceration and/or bleeding, occur usually when these melanomas have already reached a considerable thickness.
IV.10.3 Dermoscopic Criteria
To date, there have been only a few reports in the literature describing the dermoscopic patterns of scalp melanoma. However, melanomas occur- ring on the posterior scalp appear to reveal der-
moscopic features typical of melanomas on the trunk or limbs, whereas lesions on the frontal scalp frequently reveal dermoscopic features of lentigo maligna or lentigo maligna melanoma.
Thicker lesions often show an unspecific pat- tern, with ulceration or blood crusts. In our original case report [15] on the dermoscopic pat- tern of a melanoma in situ located on the balding occipital scalp of a 56-year-old man, we found the same dermoscopic features as established for melanoma on the trunk or limbs. In detail, there was an overall multicomponent pattern, com- prised of an atypical pigment network, irregular streaks, and regression structures (pepper-like granules and white scar-like areas). In another case of melanoma on the occipital scalp we ob- served again a dermoscopic pattern similar to that of melanoma on the trunk (Fig. IV.10.2). In contrast, Sahin et al. [16] reported a patient who presented clinically with a blue-to-black nodule with satellites, located on the frontal scalp and which clinically resembled melanoma. Dermo- scopic examination revealed steel blue botches and bluish perifollicular pigmentation sugges- tive of the correct diagnosis of blue nevus with satellites, as confirmed histopathologically.
However, further studies are required to investi- gate the dermoscopic patterns of a large series of melanomas and other pigmented skin lesions occuring on various areas of the scalp.
Fig. IV.10.1. Clinical view of a superficial spreading melanoma with secondary nodular component, the latter associated with the delay diagnosis. The patient sought consultation because of recent bleeding of the lesion. This melanoma shows all the criteria of the ABCDE rule, and had reached a considerably largediameter at diagnosis.
Histopathology revealed an invasive melanoma with a Breslow thickness of 4.35 mm
Fig. IV.10.2. Dermoscopy of the melanoma as shown in Fig. IV.10.1 reveals multicomponent pattern character- ized by a marked asymmetry of colors and structures.
The ulcerated nodular part essentially lacks pigmentation
and shows linear–irregular vessels as well as milky red
globules. In addition, irregular blotches and a blue-white
veil are seen
IV.10.4 Relevant Clinical Differential Diagnosis
Scalp melanoma may clinically mimic various pigmented skin tumors, such as seborrheic ker- atosis and pigmented actinic keratosis. While seborrheic keratosis can be distinguished der- moscopically from melanoma by it’s hallmark of multiple milia-like cysts and/or comedo-like openings, pigmented actinic keratosis can po- tentially mimic scalp melanoma, clinically and dermoscopically. This is because pigmented ac- tinic keratosis on the frontal areas of the scalp can exhibit grayish annular-granular structures and/or a prominent pigment pseudonetwork (rhomboidal) pattern that might be confounded with lentigo maligna. In this situation, a scaly surface and a peculiar superficial, broken-up, brown-to-black pseudonetwork can be dermo- scopic clues for the diagnosis of pigmented ac- tinic keratosis [15]. Nodular melanoma and ma- lignant blue nevus may clinically and dermoscopically reveal overlapping features to with benign blue nevi, although eventual ulcer- ation, bleeding, and/or significant asymmetry of colors and structures should leave no doubt about the actual diagnosis. However, a clinical history of lesional change might be the only clue to the correct diagnosis and should therefore al- ways raise a suspicion of melanoma on this pe- culiar body site.
IV.10.5 Histopathology
Lentigo maligna melanoma exhibits atypical melanocytes arranged in nests and as single cells along the dermo-epidermal junction, with pagetoid spread into epidermis. Epidermal atro- phy is frequently seen, and elastotic changes are invariably present in the dermis.
Superficial spreading melanoma shows vary- ingly atypical cells in nest- and single cell for- mations at all levels of the epidermis, with or without invasive component.
Nodular melanoma is defined as a dermal nodular mass of atypical melanocytes, usually composed of oval-to-round epithelioid cells with invasion of the overlying epidermis. Des- moplastic/spindle cell melanoma is character-
ized by bundles of spindle-shaped, usually amelanotic cells in the dermis which are sur- rounded by a stroma of collagen bundles. Char- acteristically, collections of lymphocytes are found in the dermis, and an overlying melano- ma in situ component is found in most cases.
IV.10.6 Management
Scalp melanoma is associated with a high inci- dence of regional disease and has a poorer prog- nosis than melanoma on other body sites; there- fore, patients may benefit from wide surgical excisions (up to 3 cm) to control local disease, in addition to elective lymph node dissection [8, 17]. Given that malignant blue nevus may develop de novo but also in a pre-existing blue nevus (cel- lular type), some groups advocate the prophylac- tic removal of all blue nevi on the scalp [18].
IV.10.7 Case Study
A 67-year-old man was referred because of mul- tiple actinic keratoses located on his bald scalp.
Clinical examination revealed numerous small erythematous scaly patches and plaques, as well as whitish scars due to lesions previously treated with cryotherapy. In addition, two brown-to- black hyperkeratotic plaques, one measuring 3 mm and the other 15¥10 mm, were observed (Fig. IV.10.3a). Clinically, the diagnosis of mul- tiple pigmented and non-pigmented actinic keratosis was made. Dermoscopy was performed on the two pigmented lesions, the small one re- vealing a blood crust with red-black homoge- neous pigmentation. No suspicious features for the diagnosis of melanoma or basal cell car- cinoma were seen and a diagnosis of irritated actinic keratosis was made. In contrast, the larg- er lesion on the parietal scalp exhibited a mar- ked asymmetry of colors and structures, includ- ing brown-to-black structureless areas or
“blotches” erythema, multiple brown dots at a
lateral edge, and features of regression (white
scar-like areas, and blue-gray dots or “pepper-
ing”) (Fig. IV.10.3b). These dermoscopic fea-
tures raised a “red flag” for melanoma and led
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us to perform a punch biopsy. The histopatho- logical specimen was characterized by a conflu- ent proliferation of oval-to-spindle melanocytes with atrophy and artifactual detachment of the overlying epidermis. The neoplastic prolifera- tion extended also into the dermis with a nevo- cytic-like deep component. A diagnosis of superficial spreading melanoma (Breslow thick- ness, 1.0 mm) was thus established.
This case underlines the problems involved in the early diagnosis of scalp melanoma. The patient was not aware of these pigmented plaques for two reasons: firstly, he did not notice this pigmented plaque when looking into the mirror due its location on the mid-scalp; and secondly, due to his baldness, he no longer re- quired a hair dresser, who might have noticed the lesion.
C
