[491] Benign Mast Cell Hyperplasia and Atypical Mast Cell Infiltrate (Mastocytosis of Undetermined Significance) in Penile Lichen Planus

Sigrid Regauer, Christine Beham-Schmid. Medical School Graz, Graz, Austria

Background: Lichen planus (LP) is a chronic, predominantly lymphocyte-mediated disease of skin and mucosa. LP occurs in the anogenital region in annular and agminated forms, but also as erosive LP on the glans penis. Erosive LP in uncircumcised men often affect the foreskin and produces a phimosis. In contrast to the lymphocytic infiltrate, the presence and type of mast cell infiltrates in LP of the foreskin and glans penis have not received much attention.
Design: 117 foreskins of adult men with LP, removed for phimosis and a histologically confirmed diagnosis of LP, were analysed for presence of lymphocytes and mast cells. The infiltrate was characterized immunohistochemically with antibodies to CD 3, 4, 8, 20, 21, 25, 30, 117c and human mast cell tryptase and analyzed for a point mutation of codon D816V of the c-kit gene and rearrangement of the T-cell receptor gamma locus (TCR@). correlated with non-erosive and erosive disease forms. Findings were correlated with non-erosive and erosive disease forms.
Results: All foreskins with LP in skin and modified mucosa revealed subepithelial mast cells in lesional skin / mucosa: 33/117 foreskins revealed <15 mast cells/mm2, 22/117 contained 16-40 mast cells/mm2 and 62/117 foreskins >40 mast cells/mm2 (average 70, range 40-100). Unaffected skin/mucosa displayed <5 mast cells/mm2. In 27/117 (23%) mast cells co-expressed CD25 and displayed spindled morphology which we termed mastocytosis of undetermined significance. Of these 27 patients, 15/27 (56%) had an erosive LP. In 5/27 foreskins a lymphocytic vasculitis of superfical and deep muscular blood vessels was identified. Neither CD30-expression nor point mutations of the c-kit gene at codon D816V were identified in the tissue infiltrates of the foreskin. Only one man had a bone marrow biopsy which revealed mast cell granulomas (systemic mastocytosis). 92 foreskins with 117 men with LP contained dense lymphocytic infiltrates. 42/88 analysed foreskins revealed T-lymphocytes with a rearranged TCR@.
Conclusions: Mast cells are an integral part of the inflammatory infiltrate of penile LP. A benign mast cell hyperplasia in lesional skin/mucosa was identified in 2/3 of patients, but in 23% of men atypical CD25-positive and spindled mast cell infiltrates were identified within lesional foreskins (mastocytosis of undetermined significance) which correlated with erosive disease and lymphocytic vasculitis. Mast cells may serve as targets for innovative therapy options for symptomatic (erosive) penile LP, particularly for those patients who are not responding to corticosteroid therapy.
Category: Dermatopathology

Monday, March 4, 2013 8:00 AM

Proffered Papers: Section F, Monday Morning


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