Alterations in collagen and elastin

Lichen sclerosus (et atrophicus)

• Blue (lymphoid band beneath zone of pallor)

• Synonymous with balanitis xerotica obliterans on the glans penis

Lichen sclerosus may involve skin or mucosa. Follicular plugging is common, and the plugs may resemble comedones clinically. The epidermis is commonly atrophic and the rete pattern is commonly effaced; however, scratching may produce pseudoepitheliomatous hyperplasia, especially in vulvar lesions. Squamous cell carcinoma rarely develops in long-standing genital lesions of lichen sclerosus and must be distinguished from pseudoepitheliomatous hyperplasia. Papillary dermal edema may produce a subepidermal bulla. Vacuolar interface dermatitis and pigment incontinence are common. Epidermotropic lymphocytes may be hyperchromatic and may mimic mycosis fungoides (Table 13.1). The differential diagnosis also includes radiation dermatitis and morphea.

Table 13-1

Features of lichen sclerosus and chronic radiation dermatitis

Feature	Lichen sclerosus	Chronic radiation dermatitis
Compact red stratum corneum	Yes	Yes
Superficial dermal pallor	Yes	Yes
Epidermal atrophy	Variable	Variable
Follicular plugging	Common	Rare
Vacuolar interface dermatitis	Yes	No
Lymphoid band	Yes	No
Pigment incontinence	Common	Usually absent
Superficial dermal vessels	Normal to slight dilatation	Widely ectatic
Radiation elastosis	No	Yes
Adnexal structures	Present	Absent
Large stellate fibroblasts	No	Yes
Deep dermis	Normal	Sclerotic
Shape of punch biopsy	Tapered	Square

Chronic radiation dermatitis

Key features

• Papillary dermal pallor without vacuolar change or lymphoid band

• Large stellate radiation fibroblasts

• Radiation elastosis

• Loss of adnexa

• Dilated ectatic vessels superficially

Fig 13-2 Chronic radiation dermatitis

Fig 13-3 Chronic radiation dermatitis

There is typically hyperkeratosis and epidermal atrophy with effaced rete that may alternate with hyperplasia. Stellate cells with large nuclei are usually present (radiation fibroblasts). The eccrine glands are atrophic and the pilosebaceous structures are absent; however, the arrector pili muscle may survive. The dermal collagen is hyalinized. Radiation elastosis may resemble solar elastosis but extends into follicular fibrous tracts. The superficial blood vessels are dilated, whereas the deeper vessels have thick walls.

The severity of radiation damage varies with the total dose, its fractionation, and the depth of penetration. Acute radiodermatitis occurs within weeks of irradiation and presents as erythema and edema followed by hyperpigmentation. Although typically diagnosed clinically, there is vacuolization and sparse degenerated keratinocytes similar to a phototoxic eruption. Chronic changes arise months to years after the initial exposure. There is atrophy, fragility, telangiectasias, altered pigmentation, and alopecia. Non-melanoma skin cancers can develop years later and may behave in an aggressive manner with increased risk of metastasis, especially in squamous cell carcinoma.

Morphea/scleroderma

Key features

• Rectangular punch

• Thick, closely packed, hyalinized collagen bundles in the lower dermis

• Loss of adventitial fat resulting in “trapped” eccrine glands

• Sparse deep lymphoplasmacytic infiltrate

• Reduced number of CD34+ cells in the dermis

• Superficial dermal pallor may be present, but the vacuolar interface dermatitis and lymphoid band of lichen sclerosus are lacking

Fig 13-8 Morphea, CD34 revealing loss of interstitial reactivity

Scleroderma encompasses a group of diseases. Localized cutaneous disease may present as morphea or linear scleroderma (including en coup de sabre). In addition to cutaneous lesions, Raynaud’s phenomenon and variable organ involvement characterize diffuse systemic scleroderma and limited systemic scleroderma (CREST). Although the histologic features are similar, morphea is usually more inflammatory and lacks the intimal thickening and luminal obliteration of vessels seen in systemic scleroderma.

There is controversy concerning the relationship of lichen sclerosus and morphea. Some regard lichen sclerosus as a superficial expression of morphea, explaining the lichen sclerosus-like changes in the papillary dermis overlying some lesions of morphea. However, lesions of morphea with superficial pallor never demonstrate a superficial lymphoid band, vacuolar interface dermatitis, or follicular plugging. Deep dermal sclerosis is always present.

The sclerotic process in linear scleroderma and deep morphea (morphea profunda) extends into the subcutaneous fat and possibly fascia and bone. Unlike chronic radiation dermatitis, radiation elastosis is absent and radiation fibroblasts are not identified. Elastic fibers in morphea are often brightly eosinophilic.

Other disorders with dermal sclerosis include sclerodermoid graft-versus-host (GvHD) disease, porphyria cutanea tarda, vinyl chloride exposure, and reactions to bleomycin. There are conflicting data regarding the relationship with Borrelia burgdorferi infection and morphea and lichen sclerosus. A relationship has been found in some studies in Europe; however other studies, especially those in North America, have resulted in negative findings.

Differential Diagnosis

Typical punch biopsies exhibit a tapered or cone-shaped outline. However, a thickened or sclerotic dermis can result in a square or rectangular biopsy. This can be seen in: