Lichen striatus. Histological, immunohistochemical, and ultrastructural study of 37 cases.

Background: Lichen striatus (LS) is a papulosquamous disorder with a distinctive linear distribution. The linearity has been shown to correspond in many cases to the pattern of Blaschko's lines. The etiology is unknown. LS can usually be identified by clinical history and histology of typical lesions. However, the histologic features are diverse and some have stated they are nonspecific.

Methods: In an effort to identify those characteristic features, we have reviewed the routine slides in 37 cases for their diagnostic criteria. Ten cases were studied further by immunohistochemistry.

Results: The patient's ages ranged from 1.3 to 49 years with mean age of 17.5 years. A female-to-male ratio was 1.6 to 1. The lesions were predominantly distributed on the extremities in 26/34 cases. The consistent histologic features were: hyperkeratosis (29/37), parakeratosis (21/37) with a few necrotic keratinocytes (28/37) in the epidermis, mild spongiosis (29/37) with exocytosis of lymphocytes (33/37). The dermal infiltrate comprised mainly lymphocytes and macrophages. At the dermal-epidermal junction, the infiltrate was either focal (20/37) or lichenoid (17/37) patterns. Superficial and deep perivascular lymphocytic inflammatory infiltrate was present in most of the cases (33/37). Appendageal involvement (34/37) was in hair follicles (24/37) or eccrine glands or ducts (22/37) or both (12/37). Satellite cell necrosis may be seen (11/37). Colloid bodies were present in 16/37 of the cases. Immunohistochemistry showed that most of the small lymphocytes in the upper dermis and epidermis were positive for CD7. Most of the lymphocytes in the epidermis were positive for CD8. CD1a Langerhans' cells were either decreased (5/10) or increased (3/10) or normal (2/10) in the epidermis.

Conclusion: The histologic diagnosis of LS can be made on the basis of the combination of these histologic features in the appropriate clinical context. Multiple biopsies may be necessary to determine whether all of these features are present in a given case.