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Kikuchi-Fujimoto disease (KFD) is a rare and benign disorder that usually occurs in young adults with enlarged lymph nodes containing infiltrate of cytotoxic T cells and nuclear debris. It can be a manifestation of systemic lupus erythematosus (SLE) although the strength of this association has varied among studies. Although specific KFD cutaneous lesions are well described, pure cutaneous lesions have never been reported. We studied a series of patients prospectively entered into a database between 2007 and 2014 with skin biopsies showing diffuse or localized inflammatory infiltrates reminiscent of cutaneous KFD, without lymph-node-related KFD. We called these skin lesions "Kikuchi disease-like inflammatory pattern" (KLIP). Twenty-nine patients, whose median age was 49 years at the time of skin biopsy, were selected and retrospectively analyzed using standardized clinical and histology charts. In skin biopsies, KLIP was localized to restricted areas within the inflammatory infiltrate (17%) or diffuse (83%), and was the only histological finding (45%) or accompanied interface dermatitis with or without dermal mucinosis (55%). Clinical dermatological findings varied widely. A definite diagnosis could be established for 24 patients: 75% had connective tissue diseases or vasculitis, mainly cutaneous lupus erythematosus (CLE) (n = 16, 67%), including 5 SLE with satisfying American College of Rheumatology criteria; 3 of the remaining patients had malignant hemopathies. CLE patients were mostly young females with acute (n = 5), subacute (n = 4), or chronic CLE (n = 6) or lupus tumidus (n = 1). Two were classified as having anti-tumor necrosis factor-alpha-induced lupus. Because two-thirds of these patients were finally diagnosed with CLE, we think that KLIP may represent a new histopathological clue for the diagnosis of lupus based on skin biopsy, requiring clinical-immunological comparison to make the correct diagnosis. KLIP should not be considered a variant of classical KFD, but rather as an elementary pattern of cutaneous inflammation, that might be the expression of the same cytotoxic process within skin infiltrates as that involved in KFD. This lesion might reflect a particular T-cell-mediated autoimmune process directed against mononuclear cells within cutaneous lupus infiltrates.

Lymphoepithelial carcinoma is a relatively common malignancy in the nasopharynx, but it rarely occurs in other sites. We report 3 additional cases of cutaneous location. Histopathologically, the tumors consisted of multiple well-circumscribed dermal-hypodermal nodules composed of aggregates of undifferentiated malignant cells. These cells had moderate amounts of eosinophilic cytoplasm and vesicular nuclei with prominent nucleoli. There was no squamous or glandular differentiation. For each case, a heavy lymphoplasmacytic infiltrate was found. No dysplasia was noted in the epidermis. In one case, the tumoral component showed numerous Sternberg-like cells scattered within a lymphocytic background. This case might be mistaken with a Hodgkin's lymphoma. Immunohistochemistry showed that the neoplastic cells were positive for cytokeratin and epithelial membrane antigen. In the present report, studying the stroma reaction cell components, we have stressed the presence of numerous factor XIIIa-positive dendritic cells in 2 cases. Because of the role of these cells in the immune response of normal stroma, their presence herein might be in relation with the favorable prognosis of this type of primary skin carcinoma. No Epstein-Barr viral genomic sequences were detected by in situ hybridization. This negativity for Epstein-Barr virus may be a help in the differential diagnosis from metastatic undifferentiated nasopharyngeal carcinoma.