Clinicopathological Features of Lymphoplasmacytic Plaque: A Retrospective Study

Objective: Lymphoplasmacytic plaque is often misdiagnosed because of its atypical clinical manifestations, leading to delayed diagnosis. Comprehensive studies of Chinese cases of lymphoplasmacytic plaque are currently lacking, particularly those examining both the clinical presentation and histopathological features. Therefore, we presented the integrated clinical and histopathological characteristics of lymphoplasmacytic plaque. Methods: We conducted a retrospective analysis of clinicopathological data from 45 patients with lymphoplasmacytic plaque, including 4 patients collected at the Hospital for Skin Diseases (Institute of Dermatology), Chinese Academy of Medical Sciences and Peking Union Medical College, from June 2014 to September 2023 and 41 additional cases previously reported in the literature. The analysis focused on focusing on epidemiological, clinical, histological features (including distinct classes of plasma cell infiltrates, interface dermatitis, epithelioid granulomas, and lymphoid follicle-like structures), treatments and outcomes. Count data were presented as constituent ratios. Results: In total, we investigated and reviewed 45 LPP cases. The median age at diagnosis was M ( Q 1 , Q 3 ), 9.00 (5.75, 16.50) years, with disease onset occurring at 6.00 (2.75, 13.50) years. Notably, lymphoplasmacytic plaque was more common in female patients (30/45, 66.7%), with a male-to-female ratio of 1:2. The most frequent site was the leg (22/45, 48.9%). Clinical features were single or multiple red-brown plaques and the peri-lesional white halo (4/45, 8.89%). Histopathologically, the predominant feature was a dense dermal lymphohistiocytic infiltrate rich in polyclonal plasma cells. Three distinct histological patterns of lymphoplasmacytic plaque in children were identified: a superficial band-like distribution (20/45, 44.5%), deep nodular and interstitial infiltration (5/45, 11.1%), and mixed type (20/45, 44.5%). Additional findings included interface dermatitis (28/45, 62.2%), epithelioid granulomas (7/45, 15.6%), and lymphoid follicle-like structures (6/45, 13.3). Immunohistochemistry demonstrated polyclonality via both kappa and lambda light chain positive expression. Conclusion: Lymphoplasmacytic plaque typically presents as a reddish-brown infiltrated plaque on the leg of pediatric patients, with histopathological features consistent with a plasma cell–rich pseudolymphomatous reaction.