Table 1. Differential Diagnosis of Mucous Membrane Plasmacytosis

Differential Diagnosis	Tests/histology specific to each disease	Differential Diagnosis	Tests/histology specific to each disease
Mucous membrane plasmacytosis	+ histologic dense subepithelial plasma cell infiltrate + histologic psoriasiform changes and acanthosis +/- erosions of epithelium	Cheilitis granulomatosa	+ histologic glaucomatous infiltrate No histologic plasma cell infiltrate No histologic psoriaform changes
Fungal Infection	Neg. fungal hyphae Neg. fungal culture No response to nystatin	Plasma cell granuloma	+ histologic granulomatous infiltrate No histologic plasma cell infiltrate No histologic psoriaform changes
Sarcoidosis	+ granuloma composed of epithelioid histiocytes, giant cell, Asteroid bodies No histologic plasma cell infiltrate No psoriaform changes	Melkerson-Rosenthal syndrome	+ histologic tuberculoid type granuloma with lymphedema + histologic banal perivascular infiltrate No histologic psoriasiform changes
Syphilis	Neg. STS No syphilis infection by silver stain No signs/symptoms of syphilis + histologic band-like perivascular infiltrate of plasma cells, lymphocytes and macrophages + psoriasiform epidermal hyperplasia and hyperkeratosis	Rhinoscleroma	+ histologic granuloma composed primarily of plasma cells + occasional Mikulicz's cells and Russell bodies + Warthin-starry silver stain of bacilli + culture for Klebsiella rhinoscleromatis + serologic tests for Klebsiella rhinoscleromatis
Lichen Planus	+ histologic superficial band of lymphocytic infiltrate + Occasional histologic hyperkeratosis No histologic plasma cell infiltrate	Plasmoacanthoma	+ discrete verrucose tumor + histologic plasma cell infiltrate + histologic plasma cell infiltrate
Cicatricial Pemphigoid	+ vesicles, erosions and ulcers of mucosa + histologic subepithelial disruption and/or ulceration No histologic psoriaform changes No histologic dense plasma cell infiltrate	Melkerson-Rosenthal syndrome	+ histologic tuberculoid type granuloma with lymphedema + histologic banal perivascular infiltrate No histologic psoriasiform changes
Allergic or contact mucositis	Inconclusive history Inconsistent distribution of lesions Neg. patch testing + histologic infiltration of monocytes and histiocytes in dermis (allergic contact dermatitis) + histologic superficial vesicles with PMNs (contact dermatitis) No improvement with removal of foreign objects/dentures	Rosai-Dorfman disease	+ histologic perivascular infiltrate of lymphocytes and plasma cells + histologic diffuse infiltration of large, foamy histiocytes in the dermis + histologic fibrosis and lymphophagocytosis No histologic psoriasiform changes
Plasmoacanthoma	+ discrete verrucose tumor + histologic plasma cell infiltrate + histologic plasma cell infiltrate	Primary cutaneous plasmacytoma	+ histologic diffuse infiltrate of plasma cells +/- histologic atypia of plasma cells + monoclonal antibody production on immunohistochemistry or gene rearrangement studies
Carcinoma	No histologic evidence of squamous cell carcinoma