Immunohistochemical Evaluation of the Quantity of Plasma Cells and Their Distribution Pattern in Zoon's Balanitis

Zoon's balanitis (ZB) is a clinical entity characterized by well-demarcated, symmetrical, red, shiny plaques located on the prepuce or glans. Clinically, it may mimic erythroplasia of Queyrat; however, unlike the latter, ZB does not exhibit epithelial dysplasia. Its hallmark histopathological feature is a dermal inflammatory infiltrate rich in plasma cells. Although the literature acknowledges variability in the number of plasma cells among cases, most reports estimate their proportion based on identification using hematoxylin-eosin (H&E) staining.

Ten cases of ZB from the past 5 years were retrieved from archival records. Immunohistochemical analyses were performed using CD138 and Treponema antibodies, alongside histochemical periodic acid-Schiff staining and the Ziehl-Neelsen histochemical technique.

In 50% of cases, plasma cell percentage evaluations obtained with H&E staining were consistent with those obtained using CD138 immunostaining. In 2 cases (20%), the percentages estimated with CD138 staining were significantly higher than those obtained with H&E. Regarding plasma cell distribution, 3 distinct patterns were identified: (1) a band-like pattern confined to the lower portion of the infiltrate. (2) Two distinct populations: one in the superficial dermis and another deeper population. (3) Scattered plasma cells throughout the inflammatory infiltrate with variable density.

Immunostaining with CD138 proved effective in confirming plasma cell percentages within inflammatory infiltrates in most cases, revealing a higher proportion than initially suspected in some instances. Notably, plasma cells frequently localized preferentially in the lower portion of the infiltrate. This finding underscores the potential for superficial biopsies to yield misleading assessments of the infiltrate's nature.