Tammie Ferringer

Lichen sclerosus (et atrophicus)

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.

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

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.

Sclerodermoid graft-versus-host disease