Plasma cells in the dermis

Plasma cells in the dermis

Most of us think Syphilis when we see a dermis full of plasma cells especially if there is a lichenoid pattern. We use the presence of plasma cells to confirm necrobiosis lipoidica rather than granuloma annulare. But there are other conditions to consider if neither of these fit the clinical situation.

Secondary syphilis

Granuloma inguinale

Rhinoscleroma

Necrobiosis lipoidica

Infiltrates surrounding epithelial tumors

Infiltrates surrounding some melanomas

Multiple myeloma

Extraosseous plasmacytoma

Macroglobulinemia of Waldenström

Rosai-Dorfman disease

AI on this topic 

In dermatopathology, the presence of plasma cells in the dermis signifies either a reactive, chronic inflammatory response (usually polytypic) or an underlying neoplastic process, such as a B-cell lymphoproliferative disorder (monotypic). [1, 2]

A robust dermal plasma cell infiltrate narrows the differential diagnosis to a specific group of conditions, primarily categorized by their underlying cause: [1, 2]

1. Infectious and Inflammatory Processes

• Syphilis (Secondary): Often shows a dense, superficial, and deep perivascular and interstitial infiltrate heavily populated by plasma cells. [1, 2, 3, 4, 5]
• Borreliosis (Lyme Disease): Displays a mixed dermal infiltrate with a prominent plasma cell component, especially in early lesions like erythema migrans. [1]
• Deep Fungal and Parasitic Infections: Conditions like leishmaniasis or granulomatous fungal infections frequently recruit plasma cells. [1]
• Mucocutaneous Diseases: Plasma cells are characteristically found in Plasma Cell Mucositis (Zoon Balanitis) and Plasma Cell Cheilitis. [1, 2, 3]
• Chronic Irritation/Trauma: A few scattered plasma cells can be an incidental sign of chronic inflammation, particularly near ulcers, scars, or around non-melanoma skin cancers (e.g., basal cell carcinomas). [1, 2]

2. Primary and Secondary Neoplasms

• Primary Cutaneous Marginal Zone Lymphoma (PCMZL): An indolent B-cell lymphoma that presents with a dense, diffuse, or nodular dermal infiltrate of monoclonal plasma cells, small lymphocytes, and centrocytes. [1, 2, 3, 4]
• Plasmacytoma (Multiple Myeloma): Skin lesions may arise as part of a systemic plasma cell dyscrasia or as primary cutaneous plasmacytoma. [1, 2, 3, 4, 5]

3. Immunoglobulin & Protein Deposition

• Amyloidosis: The breakdown of immunoglobulins from plasma cells can result in the dermal deposition of AL amyloid.
• Cryoglobulinemia: Characterized by circulating immune complexes that often trigger dermal plasma cell presence due to inflammation. [1, 2, 3, 4]

4. Dermal Plasmacytosis

• Cutaneous Plasmacytosis: A rare, benign disease predominantly characterized by reddish-brown nodules and a dense polyclonal infiltrate of mature plasma cells in the dermis. [1, 2, 3, 4]

Key Diagnostic Tools:

To distinguish between benign/reactive (polytypic) and malignant (monotypic) infiltrates, dermatopathologists rely on: [1, 2]

• Immunohistochemistry (IHC): Plasma cells strongly stain for CD138 and CD38.
• Light Chain Restriction: Flow cytometry or immunohistochemical testing for Kappa (\(\kappa \)) and Lambda (\(\lambda \)) light chains is used. A normal reactive process will show a polytypic mix (e.g., a \(\kappa:\lambda\) ratio of roughly \(2:1\)), whereas neoplasms will show monoclonality. [1, 2]