White : Diseases of the Skin - Disorders and Tumors of Skin Appendages

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Gary M. White & Neil H. Cox

Diseases of the Skin

23	Disorders and Tumors of Skin Appendages

BENIGN SKIN APPENDAGE NEOPLASAMS

There are an immense number of follicular neoplasms, most with complicated names, many of which cannot be diagnosed clinically. There are a few general points about this group of disorders that are most notable.

•	Most are benign.
•	Many can occur as solitary or multiple types, the multiple types often being familial and having an earlier age of onset compared with the solitary versions.
•	Some may occur together (such as hereditary trichoepitheliomas with cylindromas, or fibrofolliculomas with trichodiscomas).
•	Some are markers of internal disorders, particularly the association of both benign and malignant sebaceous gland tumors with polyposis and carcinoma of colon.
•	Most are clinically non-specific and may resemble each other, or appear similar to several other benign or malignant conditions.

They can be histologically classified by the appendage from which they originate (Table 23.1).

Fig. 23.25 Trichodiscomas: these may occur in isolation or as multiple lesions, as in this patient. They may also be associated with trichofolliculomas, from which they are clinically indistinguishable (see Fig. 23.23).

Fig. 23.26 Multiple fibrofolliculomas in a patient with Birt-Hogg-Dube syndrome (multiple fibrofolliculomas and acrochordons). Trichodiscomas may also be associated, and there is a link with colonic polyps and neoplasia.

Fig. 23.27 Cowden syndrome. Multiple trichilemmomas, hamartomas, and fibrous lesions may be associated with tumors of breast, thyroid, and colon. (Courtesy of Michael O. Murphy, M.D.)

Fig. 23.28 Eruptive vellus hair cysts on the trunk of a young woman. These lesions were asymptomatic, but she was very aware of the cosmetic appearance. Some of the larger lesions were ablated with electrocautery.

Tumors of the hair apparatus

Cylindroma

These lesions typically occur on the scalp, face, or neck. They are usually purplish to red nodules (Fig. 23.18a,b) and are one of the few appendage neoplasms that are usually characteristic clinically. Most are solitary or few in number, but multiple lesions may occur, and some lesions become very large (‘turban tumor’). There is a familial association with multiple facial trichoepitheliomas (Spiegler-Brooke syndrome, Fig. 23.18c).

Pilomatricoma and other follicular neoplasms

Lesions of pilomatricoma (calcifying epithelioma of Malherbe) are not uncommon. They occur most often in the first half of childhood, but a further peak of incidence occurs in the sixth and seventh decades. The origin is from the hair matrix. There is an association between multiple familial pilomatricomas and myotonic dystrophy.
The clinical appearance is quite variable. Most lesions occur on the face or upper limbs. Many pilomatricomas appear as nodules that resemble epidermoid cysts but are typically very hard, and often have a multilobulated feel (Figs 23.19 and 23.20). Some of these are deeply situated and palpable rather than visible. However, some are more superficial and inflammatory, resembling pyogenic granulomas; this type of lesion often extrudes small pieces of calcified material. They may also resemble malignant epidermal tumors in older patients.

Fig. 23.29 A flat organoid nevus in a young child; note the yellow-orange color and cobblestoned texture.

Fig. 23.30 Organoid nevi. In the second half of childhood, these lesions typically become more cobblestoned (a) or frankly verrucous (b); these are normal changes but may prompt referral due to increased wartiness of a previously fairly flat lesion.

Other follicular neoplasms (Figs 23.21 - 23.27) include inverted follicular keratosis, trichoepithelioma, trichofolliculoma, trichilemmoma, trichodiscoma, infundibular tumor, and fibrofolliculoma. Many of these may be clinically difficult to distinguish, although there may be useful features such as keratin plugs in inverted follicular keratosis or multiple tiny hairs in trichofolliculoma.

Fig. 23.31 A large, warty organoid nevus in the preauricular skin.

Fig. 23.32 A benign warty area developing within an organoid nevus on the forehead. In this case, in a prepubertal child, the warty area responded to cryotherapy without removal of the entire lesion.

Fig. 23.33 Smooth nodules developing within organoid nevi, in both cases due to basal cell carcinoma. The pinna (a) is a less common site for organoid nevi than the scalp (b). (Panel a courtesy of Michael O. Murphy, M.D.)

Fig. 23.34 A crusted nodule developing within an organoid nevus. (Courtesy of Michael O. Murphy, M.D.)

Fig. 23.35 A large basal cell carcinoma arising within an organoid nevus in the retroauricular crease. Basal cell carcinoma is the most common of the malignant lesions that may occur within this type of hamartoma.

Fig. 23.36 Steatocystoma multiplex on the trunk, with rather acne-like cysts. There is no simple treatment, and these lesions often do not warrant surgical intervention.

Fig. 23.37 Much larger nodules of steatocystoma multiplex for which the only treatment is excision.

Fig. 23.38 Hidrocystoma in the axilla. These lesions often have a blue or brownish color.

Eruptive vellus hair cysts

Eruptive vellus hair cysts are typically multiple, in large numbers, usually on the trunk. They may be skin-colored but often have a blue or brown color (Fig. 23.28). They contain large numbers of coiled up, tiny hairs.

Fig. 23.39 Dark-brown fluid content from a hidrocystoma. This appears blue
in vivo due to the way that light is refracted through the skin, a mechanism known as the Tyndall effect (discussed in Ch. 8 with regard to colors in lichen planus).

Fig. 23.40 (a,b) Examples of apocrine hidrocystomas on the eyelid margins. This is a common site for these lesions, where they may be clinically difficult to distinguish from cystic basal cell carcinomas. (b) also shows sebaceous hyperplasia. (Panel b courtesy of Dr. G. Dawn.)

Fig. 23.41 Hidradenoma papilliferum presents as a vulval nodule, which is benign but may be confused with squamous cell carcinoma.

Fig. 23.42 Apocrine lesions often occur in the region of the nipple, in this case a disorder known as erosive adenomatosis. (Courtesy of Michael O. Murphy, M.D.)

Fig. 23.43 Syringomas on the eyelids, a typical site. They are usually skin-colored or slightly white in pale skins, but may be browner in East Asian or darker skin. Physical destruction with laser or electrocautery may be warranted, but recurrences are common, as the lesions are relatively deep in the skin.

Fig. 23.44 Multiple syringomas. The pelvic region is a common site for these eruptive lesions (a). When they occur on the penis (b) or vulva (c), they may cause diagnostic confusion, as they resemble sebaceous glands (see Fig. 23.17). (Panel a courtesy of Dr. G. Dawn.)

Fig. 23.45 Eruptive syringomas may produce large numbers of lesions that are usually rather brown. These may affect relatively localized areas of the skin, such as the flanks or pubic area, or may be generalized.

Fig. 23.46 Eccrine spiradenoma is a rather non-specific, small nodule, flesh colored or slightly telangiectatic, which may resemble a small basal cell carcinoma but is often painful.

Fig. 23.47 Eccrine poromea. (a,b) Examples of a smooth and a more warty eccrine poroma at a typical site on the sole of the foot. These lesions may have a wide differential diagnosis, and may be difficult to remove due to the lack of loose skin at this site.

Fig. 23.48 Eccrine poromea. There is often a rather vascular appearance in eccrine poromas, especially if they occur at non-glabrous skin sites. This lesion on the arm could be mistaken for a pyogenic granuloma.

Tumors of the sebaceous apparatus

Nevus sebaceus (organoid nevus)

This is a common hamartoma, consisting mainly of abnormal sebaceous gland structures (Figs 23.29-23.35). They usually occur on the scalp, and have a typical orange-colored and cobblestoned appearance. In early childhood, they are usually fairly flat, but may be noticed as an area of alopecia. Most present at puberty when they become thickened with a warty or mulberry-like pattern, and may be mistaken for nevi or warts. They can give rise to a wide variety of skin appendage neoplasms, such as syringocystadenoma papilliferum. Their importance, apart from their nuisance value, is that development of basal cell carcinoma is relatively common in these lesions (possibly 25%), so most are excised prophylactically in later childhood (see also Fig. 19.21).
A more extensive, ‘systematized’ version of organoid nevi is rare but may be associated with ocular and ‘neurologic abnormalities.

Steatocystoma multiplex

Steatocystoma multiplex is a disorder in which there are multiple cysts, usually most prominent on the trunk, which resemble epidermoid cysts but are sebaceous (Figs 23.36 and 23.37). They may be inflamed, and resemble acne on the chest, and occasionally they reach a large size. There is no simple treatment, although antibiotics or systemic retinoids have some effect on inflammatory lesions; individual troublesome lesions may require excision.

Fig. 23.49 Fibrous papule on the nose. These lesions are small angiofibromas, but may often be difficult to distinguish from benign appendage neoplasms.

Fig. 23.50 Sebaceous carcinoma, in this case occurring on the temple as a crusted nodule resembling squamous cell carcinoma. The crusting has been removed to demonstrate a very vascular nodule, again of non-specific morphology.

Tumors of the apocrine apparatus

Apocrine hidrocystomas are relatively common tumors on the face, particularly the eyelid margin. When deeply situated, they often look quite blue due to a brownish fluid content. Eccrine hidrocystomas look clinically identical and may have the same brown fluid content. Most around the eyes are more superficial and grayish with surface telangiectasia, closely resembling cystic basal cell carcinoma (Figs 23.38-23.40).
Hidradenoma papilliferum occurs mainly on the vulval skin (Fig.23.41). Apocrine lesions also have a predisposition to occur in axillae and on the breast (Fig. 23.42).

Tumors of the eccrine apparatus

Syringomas

These tumors arise from eccrine ducts (Figs 23.43-23.45). They are a common and often incidental finding on the eyelids, where they are multiple, skin-colored, or slightly pale, and of cosmetic concern only. They appear to be especially common in Asian skin.
Eruptive syringomas are a much less common disorder. They are skin-colored or brownish papular lesions, which may appear in large numbers, usually on the neck or trunk. Chondroid syringomas are an uncommon but histologically characteristic type of syringoma, which arise as a solitary nodule at any body site. Eccrine spiradenomas appear similar but are solitary lesions (Fig. 23.46).

Fig. 23.51 Sebaceous epithelioma in the scalp, a relatively uncommon site. Like sebaceous carcinomas, the appearance is often that of a non-specific nodule that resembles basal or squamous cell carcinoma. Although the term sebaceous epithelioma may become obselete, it is still used here as being the pathologic diagnosis at the time.

Fig. 23.52 Sebaceous adenoma. These lesions are clinically non-specific but may be a marker of internal malignancy. Any sebaceous tumor may have this same significance.

Eccrine poroma

These tumors occur especially on the sole or border of the foot (Fig. 23.47). They are usually pink to red, elevated plaques that may indent the thick plantar skin to form a groove or moat around them. They may be clinically mistaken for warts, pyogenic granulomas (Fig.23.48), squamous cell carcinoma, or amelanotic melanoma. Excision may be difficult due to the site, but is curative; malignant eccrine poroma is very rare.

Other eccrine nodules

Syringocystadenoma papilliferum is most often found on the scalp in association with organoid nevi.

Differential diagnosis of benign skin appendage tumors

This includes the following.

•	Malignant neoplasms-especially basal cell carcinoma (particularly in the differential of cystic lesions), less often squamous cell carcinoma or rarer tumors such as Merkel cell carcinoma.
•	Benign nodules-nevus, sebaceous hyperplasia, epidermoid cysts, angiofibromas, and fibrous papule (Fig. 23.49).
•	Localized infections-viral warts and molluscum contagiosum.

PRACTICE POINTS

•	Most appendage tumors are benign.
•	Most are clinically non-specific nodules, often on the head and neck.
•	Many can occur as solitary or multiple types, the multiple types often being familial.
•	Some are markers of internal disorders, particularly the association of both benign and malignant sebaceous gland tumors with polyposis and carcinoma of colon.