**6. Neoplasms of scalp**

The diagnosis of head lice infestation is made through finding viable eggs [nits], nymphs and live adult lice. For the diagnosis, the use of a louse comb is more efficient than direct visual examination of the scalp [76]. Examining suggestive particles under the microscope may be helpful to confirm the diagnosis. Non-contact dermoscopy is also a useful instrument for differentiate nymph-containing eggs from empty cases or pseudonits [72]. Histology is rarely required for diagnosis. Examination of a louse bite reveals intradermal haemorrhage and a

Differential diagnosis of head lice includes seborrheic scales, hair casts [inner root sheath remnants], pityriasis amiantacea, white piedra, black piedra, impetigo, pili torti and monilethrix. It should kept in mind that, in contrast to nits, hair casts are freely movable along hair shaft [72]. Basically, therapeutic wet combing, topical application of a pediculicide and oral treatment [Trimethoprim-sulfamethoxazole and ivermectin] are used to eliminate head lice. Wet combing is a mechanical removal of the lice. The patients must comb their wet hair with a fine-toothed comb every 3–4 days for a total of 2 weeks. If all young lice are combed out a few days after hatching, the infestation can be eradicated completely. Pediculicides are the most effective treatment for head lice. They can be divided into three types. Pediculisides with neurotoxic mode of action are permetrin [Nix®], pyrethrin [Rid®], malathion [Ovide®], carbaryl, lindan [Kwell®] and spinosad [Natroba®]. Dimeticones [Nyda®, Hedrin®], isopropyl myristate [Resultz®] and 1,2-octanediol are the pediculicides with physical mode of action. The other group of pediculicides is plant-based pediculicides. All topical preparations are

Because permetrin and pyretrin are non-ovicidal, they should be reapplied on days 7 and 13–15. Permethrin 1% is a synthetic pyrethroid and is approved for use in children aged 2 months or older. It shows neurotoxic effect by inhibiting the sodium ion flux through nerve cell membrane channels [68]. It should be applied on damp unconditioned hair for 10 min and then rinsed off. Pruritus, erythema and edema are its usual side effects [77]. Pyretrin is used for children aged 2 years and older. Malathion is a cholinesterase inhibitor. It is approved for use in individuals aged 6 years or older. Both malathion and lindan are ovicidal. Spinosad is ovicidal, killing both eggs and lice and also kills permethrin-resistant populations of lice. It is approved in patients aged 4 years and older [78]. Oral ivermectin is administered a single dose of 200 μg/kg and repeated in 10 days. It is restricted to children older than 5 years and

Resistance of lice to the pediculocides is an important problem. Spinosad, benzyl alcohol 5% or malathion 0.5% may also be used, in case of resistance, for those older than 6 and 24 months, respectively. Another treatment option is manual removal of nits [especially the ones within 1 cm of the scalp]. It is recommended after treatment with any product. Besides these treatments, occlusive agents such as petroleum jelly, vinegar, isopropyl alcohol, olive oil, mayonnaise and melted butter can been used once per week for 3 weeks to suffocate the

Patients with head lice should have laundered potential fomites [e.g., towels, pillowcases, sheets, hats, toys] with hot water [at least 130°F/55°C] and then dried in a dryer using the

deep, wedge-shaped infiltrate with many eosinophils and lymphocytes.

used for two or three applications, 1 week apart [68, 71].

weighing at least 15 kg [71].

lice [68, 78].

210 Hair and Scalp Disorders

The neoplasms of the scalp consist of large group of different diseases due to arising different origin. They can be divided into two groups: benign and malignant. They can be categorised as shown in **Table 1**. The common benign swellings of the scalp are the epidermoid cysts, trichilemmal cysts, lipomas, dermoid cyst, pilomatrixoma, steatocystoma multiplex and cylindroma. In this section, neoplasms especially which is most seen and is arising from scalp are discussed in detail.


**Table 1.** The neoplasms of the scalp.

#### **6.1. Trichilemmal cyst**

Trichilemmal cyst [TC] also known as 'pilar cyst' is an adnexal tumour that arises from outer root sheath of the hair follicle. It is almost always benign but may be locally aggressive. Malignant transformation is very rare but may lead to distant metastases [77, 79].

It affects 5–10% of the population with a female preponderance [77, 80]. TC may be sporadic or they may be inherited as an autosomal dominant trait. It presents as an asymptomatic or mildly painful firm nodule but frequently they are multiple. The cysts are classically located in areas bearing hair follicle, mostly on the scalp and rarely the face, trunk and extremities may be involved. They are usually 1–2 cm in size but can be much larger.

Histopathologic evaluation can confirm the diagnosis. Histopathologically TCs are lined by stratified squamous epithelial cells and consist homogenous eosinophilic material that frequently show foci of calcification and abrupt keratinisation without an intervening granular layer.

TC may be misdiagnosed as epidermal cyst clinically but unlike epidermal cyst, no punctum is seen. Treatment is by complete excision. Trichilemmal cysts typically can be extracted more easily than epidermoid cysts [77, 79, 80].

#### **6.2. Proliferating trichilemmal cyst**

Proliferating trichilemmal cyst [PTC] also known as proliferating pilar tumour is a rare neoplasm arising from the isthmus region of the outer root sheath of the hair follicle. It can be inherited in an autosomal dominant pattern. It occurs most commonly on the scalp in women older than 50 years. Most tumours arise within a pre-existing trichilemmal cyst but some PTCs arise *de novo* [81]. They have different clinical and histologic features from trichilemmal cyst. PCTs may slowly or rapidly grow into a large, solitary, well-circumscribed painless mass overlying alopecia. The size may range from 1 to 10 cm, although there have been reports of lesions exceeding 25 cm in diameter. Inflammation, ulceration, bleeding and/or yellowish discharge may occur and may be clinically confused with squamous cell carcinoma. They usually behave in a benign nature but malignant transformation with local invasion and metastasis has also been described [82, 83].

Broad anastomosing bands and lobules of squamous epithelium in the cyst wall are the histologic features of PCT. PTC shows features of typical trichilemmal cyst, but additionally shows extensive epithelial proliferation, variable cytologic atypia and mitotic activity. Complete excision is recommended for the treatment of PCT owing to their potential for locally aggressive behaviour and malignant transformation [81, 83]. If malignant PTC with multi-nodal metastasis is identified, wide local excision with 1-cm margins should be performed, followed by adjuvant chemotherapy and radiation to prevent recurrence [84].

#### **6.3. Nevus sebaceous**

Nevus sebaceous [NS] is uncommon hamartomatous lesions that exhibits epidermal, follicular, sebaceous and apocrine malformation to varying degrees. It was first described by Jadassohn in 1895. It occurs most commonly on the head and neck while similar lesions elsewhere on the body are termed verrucous epidermal nevi. It often presents at birth with an incidence of 0.5–1% [85]. The characteristic clinical feature is a well-circumscribed, flesh-coloured, bald patch on the scalp at birth. At puberty, lesion grows proportionally with the patient and tends to be slightly yellow or orange, thick, velvety and verrucous surface. Familial cases have been reported [86].

Development of benign or malignant adnexal neoplasms may occur in NS, usually in adulthood. Syringocystadenoma papilliferum and trichoblastoma are the most common benign tumours arising in NS [87]. Other benign tumours include trichilemmoma, sebaceous adenoma, apocrin adenoma and poroma. Malignant transformation can develop in 10–15% of lesions in some series and basal cell carcinoma is the most seen malignant tumour. Actually, this rate is less than 1% of cases. Development of six different tumours has also been reported in one solitary lesion [88].

Histologically, early lesions show few abnormal features. A few misshapen hair follicles and small apocrine glands may be identifiable during childhood. At adolescence, as the lesions clinically thicken, NS looks like an epidermal nevus, with papillated epidermal hyperplasia, abortive hair follicles and enlarged apocrine glands.

The lesions must be distinguished from aplasia cutis congenita, congenital nevi, epidermal nevus syndrome and seborrheic keratosis. Although there is no consensus regarding the NS, increasing to the possibility of malignant tumour outgrowth from a NS with age, it is necessary to prophylactic excision especially in adulthood. Photodynamic therapy with topical aminolevulinic acid is another treatment option for non-surgical treatment [89].

### **6.4. Cylindroma**

It affects 5–10% of the population with a female preponderance [77, 80]. TC may be sporadic or they may be inherited as an autosomal dominant trait. It presents as an asymptomatic or mildly painful firm nodule but frequently they are multiple. The cysts are classically located in areas bearing hair follicle, mostly on the scalp and rarely the face, trunk and extremities

Histopathologic evaluation can confirm the diagnosis. Histopathologically TCs are lined by stratified squamous epithelial cells and consist homogenous eosinophilic material that frequently show foci of calcification and abrupt keratinisation without an intervening

TC may be misdiagnosed as epidermal cyst clinically but unlike epidermal cyst, no punctum is seen. Treatment is by complete excision. Trichilemmal cysts typically can be extracted more

Proliferating trichilemmal cyst [PTC] also known as proliferating pilar tumour is a rare neoplasm arising from the isthmus region of the outer root sheath of the hair follicle. It can be inherited in an autosomal dominant pattern. It occurs most commonly on the scalp in women older than 50 years. Most tumours arise within a pre-existing trichilemmal cyst but some PTCs arise *de novo* [81]. They have different clinical and histologic features from trichilemmal cyst. PCTs may slowly or rapidly grow into a large, solitary, well-circumscribed painless mass overlying alopecia. The size may range from 1 to 10 cm, although there have been reports of lesions exceeding 25 cm in diameter. Inflammation, ulceration, bleeding and/or yellowish discharge may occur and may be clinically confused with squamous cell carcinoma. They usually behave in a benign nature but malignant transformation with local invasion and

Broad anastomosing bands and lobules of squamous epithelium in the cyst wall are the histologic features of PCT. PTC shows features of typical trichilemmal cyst, but additionally shows extensive epithelial proliferation, variable cytologic atypia and mitotic activity. Complete excision is recommended for the treatment of PCT owing to their potential for locally aggressive behaviour and malignant transformation [81, 83]. If malignant PTC with multi-nodal metastasis is identified, wide local excision with 1-cm margins should be performed, followed

Nevus sebaceous [NS] is uncommon hamartomatous lesions that exhibits epidermal, follicular, sebaceous and apocrine malformation to varying degrees. It was first described by Jadassohn in 1895. It occurs most commonly on the head and neck while similar lesions elsewhere on the body are termed verrucous epidermal nevi. It often presents at birth with an incidence of 0.5–1% [85]. The characteristic clinical feature is a well-circumscribed, flesh-coloured, bald patch on the scalp at birth. At puberty, lesion grows proportionally with the patient and tends to be slightly yellow or orange, thick, velvety and verrucous surface. Familial cases have been reported [86].

by adjuvant chemotherapy and radiation to prevent recurrence [84].

may be involved. They are usually 1–2 cm in size but can be much larger.

granular layer.

212 Hair and Scalp Disorders

easily than epidermoid cysts [77, 79, 80].

metastasis has also been described [82, 83].

**6.3. Nevus sebaceous**

**6.2. Proliferating trichilemmal cyst**

Cylindroma is a benign skin adnexal tumour differentiating towards either the eccrine or apocrine line. It has two different clinical presentations, solitary and multiple. Solitary cylindroma is a slow growing, benign tumour effecting the scalp especially the capillitium and neck region. Solitary cylindromas affect middle-aged and elderly persons and female-to-male ratios are 6:1 and 9:1 [90].

Multiple cylindromas are very rare and inherited in an autosomal dominant pattern by mutations in CYLD1, a tumour suppressor gene. They frequently occur on the scalp and rarely on the trunk. The term turban tumour is used to describe multiple cylindromas. Since the nodules enlarge and coalesce on the scalp, the patient looks as wearing a turban. Multiple cylindromas should suggest of Brook-Spiegler syndrome, which has been characterised by the development of multiple skin appendage tumours, such as cylindromas, trichoepitheliomas and spiradenomas [91, 92].

Histopathology is diagnostic with islands of basaloid cells in a jigsaw puzzle-like pattern separated by hyaline basement membrane material that is PAS positive. Eosinophilic PASpositive hyaline material in globules is also seen within the lobules [93].

Differential diagnosis of cylindroma includes trichilemmal cysts, basal cell carcinoma, spiradenoma and dermatofibroma. Under dermatoscopy, cylindromas demonstrates arborising telangiectasia and scattered white globules on a background of white to salmon-pink. Vascular branches can be seen at the periphery which may extend into the centre of the lesion [94].

For solitary lesions, the treatment option is complete excision. Other treatments include electrodesiccation/curettage, cryotherapy and carbon dioxide laser. The patients with multiple cylindromas should follow up because of the tendency for new lesions to develop [95].
