Benign lichenoid keratosis: a clinical and pathologic reappraisal of 1040 cases

Benign lichenoid keratosis, otherwise known as lichen planus-like keratosis, is a common, cutaneous entity that is often confused with cutaneous malignancy. Few studies have examined the multiple clinical and pathologic guises of this entity, particularly within the context of clinical pathologic correlation or magnitude of this study. We examined the epidemiologic, clinical, and pathologic attributes of 1040 consecutive cases of benign lichenoid keratosis referred for pathologic examination at a busy laboratory over an entire year. Clinical parameters assessed included the age, anatomic location, gender, and multiplicity of the lesions. Pathologic attributes were assessed yielding discernment of five different subtypes that included a classic type, bullous type, atypical type with cytologically atypical lymphocytes, an early or interface type, and a late regressed or atrophic type. The results yielded an average age at presentation of 59.5 years with an age range of 36 to 87 years. The gender frequency was 76% female, 24% male. The trunk was the most common location (76%), followed by the extremities (33%) and head and neck (7%); 8% of patients presented with two lesions and less than 1% with three lesions prompting consideration of lichen planus. The classic, atypical, and bullous forms of the disease clinically presented with erythematous papule/plaque(s). The early or interface type showed erythematous to hyperpigmented brown macules and the regressed or atrophic type presented as violaceous papules or irregularly distributed macular pigmentation; 81% of the lesions showed the classic histology consisting of epidermal acanthosis with a band-like lichenoid lymphocytic infiltrate. Variable numbers of plasma cells, eosinophils, and neutrophils were identified as well as epidermal parakeratosis distinguishing these lesions from typical lichen planus. The bullous variant showed intraepidermal or subepidermal bullous cavities with a dense associated lymphocytic infiltrate and increased numbers of necrotic basilar layer keratinocytes. The atypical variant showed features of the classic type with scattered enlarged CD-3, CD-30 (+) lymphocytes possessing hyperchromatic, irregular nuclei. The early interface type showed single lymphocytes aligned along the dermoepidermal junction without epidermal acanthosis and adjacent lentigo. The regressed or atrophic variant showed epidermal atrophy with papillary dermal scarring, patchy lymphocytic infiltrates and melanin incontinence. The clinicopathologic spectrum of benign lichenoid keratosis is broad and encompasses several unrelated entities. An awareness of its expanded presentation is essential to avoid misdiagnosis and may serve as an important forerunner of pathogenic discernment.