A 38-year-old woman presents with a well-demarcated, scaly, erythematous plaque with central atrophy on her right cheek. The lesion has been slowly enlarging over the past 6 months. She reports no systemic symptoms. A punch biopsy is performed, and the histopathology is shown below.

Based on the histopathologic findings, which of the following diagnoses is most likely?

A. Psoriasis vulgaris

B. Lichen planus

C. Subacute cutaneous lupus erythematosus

D. Discoid lupus erythematosus

E. Dermatomyositis

Rationale: 

The histologic features are most consistent with answer choice D. Discoid lupus erythematosus (DLE) is characterized histologically by a vaculoar interface dermatitis, hyperkeratosis with follicular plugging, epidermal atrophy, mucin deposition, and superficial and deep perivascular and periadnexal lymphocytic infiltrate as seen above. 

Incorrect answer choices:

A. Psoriasis vulgaris typically shows regular acanthosis, parakeratosis, neutrophils in the stratum corneum (Munro microabscesses), and thinned suprapapillary plates. Interface change or basement membrane thickening are not observed. 

B. Lichen planus features sawtooth acanthosis, dense band-like lymphocytic infiltrate at the dermoepidermal junction, hypergranulosis, and Civatte bodies, but no follicular plugging or dermal mucin.

C. Subacute cutaneous lupus erythematosus does share some features with DLE  including vacuolar interface change and mucin deposition but has minimal follicular plugging and is typically less scarring and atrophic.

E. Dermatomyositis biopsy can show interface dermatitis, epidermal atrophy, and dermal mucin, but follicular plugging is typically absent, and clinical findings (heliotrope rash, Gottron papules, shawl sign, holster sign, V-neck sign) are essential for diagnosis.

Additional reading at Barnhill's Dermatopathology Chapter 3: Interface Dermatitis