120: Cutaneous Pseudolymphoma Flashcards
What is cutaneous pseudolymphoma?
Cutaneous pseudolymphoma is a group of skin diseases characterized as benign lymphoproliferative processes that clinically and/or histologically simulate cutaneous lymphomas.
What are the infectious agents that can cause cutaneous pseudolymphoma?
Infectious agents include spirochetal bacteria (e.g., Borrelia burgdorferi, Treponema pallidum), viruses (e.g., parapoxviruses), infestations (e.g., scabies, insect bites), injection of vaccines and allergens for hyposensitization, foreign bodies (e.g., tattoos, metals), drugs, and idiopathic causes.
What are the classifications of cutaneous pseudolymphoma?
The classifications include: 1. Nodular PSL simulating clinically and histologically T-cell or B-cell lymphoma 2. PSLs mimicking histologically mycosis fungoides (pseudo-MF) 3. Other skin disorders with lymphocyte-rich infiltrates 4. Benign intravascular proliferation of lymphocytes (simulating intravascular lymphoma).
What is the diagnostic approach for cutaneous pseudolymphoma?
The diagnostic approach includes clinical presentation, histologic analysis, molecular studies, and diagnostic workup.
What is the clinical course of cutaneous pseudolymphoma?
The clinical course is highly variable: resolution may occur after biopsy, some lesions may persist for months or years, and recurrences can occur, especially after reexposure to the inducing agent.
What are the treatment options for nodular pseudolymphoma?
Treatment options include complete surgical excision, topical or intralesional corticosteroids, cryotherapy, or laser therapy. If not successful, radiation therapy may be considered.
What are the common clinical features of cutaneous B-cell pseudolymphoma?
- Most commonly presents with a nodule or plaque.
- Commonly involved sites include the face, especially the nose and cheeks, upper trunk, and arms.
- Male-to-female ratio is 2:1.
- Approximately 67% of patients are younger than 40 years, with less than 10% being children and adolescents.
- Most common presentation is a localized form with a solitary nodule measuring up to 4 cm.
What histological features are characteristic of nodular B-cell pseudolymphoma?
- Dense nodular infiltrate predominantly located in the reticular dermis.
- Composed mostly of small lymphocytes with chromatin dense nuclei.
- Presence of reactive germinal centers with tingible body macrophages.
- Lymphocytes do not show nuclear atypia.
- Admixture of plasma cells, which are diffusely scattered.
- Possible presence of eosinophils and a granulomatous component in some cases.
What immunophenotyping characteristics are observed in cutaneous B-cell pseudolymphoma?
- Majority of the infiltrate consists of CD19+, CD20+, and CD79a+ B cells.
- Reactive follicles show (+) bcl-6 and (-) bcl-2.
- Small B cells in the interfollicular area show (-) bcl-6 and (+) bcl-2.
- Networks of CD21+ follicular dendritic cells are sharply demarcated and regularly structured.
What are the differential diagnoses for cutaneous B-cell pseudolymphoma?
Diagnosis | Key Features |
|———–|————–|
| Primary cutaneous marginal zone lymphoma (PCMZL) | - Nodular infiltrates in the reticular dermis and superficial subcutis.
- Plasma cells are more prominent and found in sheets.
- Monotypic expression of Ig light chains with a ratio of at least 5:1. |
| Primary cutaneous follicle center lymphoma (PCFCL) | - Predominance of centrocyte-like differentiated tumor cells.
- Low proliferative activity in neoplastic follicles.
- Clonal B-cell population detected in the majority of cases. |
What are the potential etiological factors associated with cutaneous pseudolymphoma?
- Borrelia burgdorferi infection, insect bites, or injection of vaccines or antigens for hyposensitization.
- Acupuncture treatment, tattoos, metals in piercing rings and earrings, and drugs.
What is the clinical significance of pseudoclonality in B-cell pseudolymphomas?
Pseudoclonality represents a diagnostic pitfall and must be ruled out in lesions with subtle infiltrates to avoid misdiagnosis.
What histological features differentiate primary cutaneous follicle center lymphoma (PCFCL) from B-cell pseudolymphoma (PSL)?
PCFCL shows predominance of centrocyte-like differentiated tumor cells, low proliferative activity in neoplastic follicles, and irregular networks of CD21+ follicular dendritic cells. B-cell PSLs have high proliferative activity in reactive germinal centers, sharply demarcated CD21+ networks, and readily identifiable tingible body macrophages.
What is the role of hydroxychloroquine in treating multiple pseudolymphoma lesions?
Hydroxychloroquine inhibits the activity of plasmacytoid dendritic cells, which are found in the majority of B-cell pseudolymphomas and may drive the condition.
What is the clinical presentation of lymphocytoma cutis?
Lymphocytoma cutis presents with a solitary nodule or plaque, often on the face, upper trunk, or arms, with a male-to-female ratio of 2:1.
A patient presents with a solitary red to violaceous dome-shaped nodule on the earlobe. What is the likely diagnosis and the associated pathogen?
The likely diagnosis is Borrelia-associated B-cell pseudolymphoma, caused by Borrelia burgdorferi infection.
What is the first-line therapy for Borrelia-associated B-cell pseudolymphomas?
Antibiotics are the first-line therapy for Borrelia-associated B-cell pseudolymphomas, which help prevent other complications from Borrelia infection, such as arthritis and carditis.
What are the clinical features of T-cell and mixed pseudolymphoma?
T-cell and mixed pseudolymphoma usually presents with a solitary or multiple red to violaceous nodules similar to B-cell pseudolymphoma.
What is the significance of clonality studies in T-cell pseudolymphomas?
Clonality studies show a polyclonal infiltrate in the majority of T-cell pseudolymphomas, while clonal pseudolymphomas may progress to overt lymphoma and represent very early stages of lymphomagenesis.
What are the differential diagnoses for cutaneous T-cell pseudolymphoma?
Differential diagnoses include: 1. Cutaneous CD4+ small-/medium-sized T-cell lymphoma - solitary lesion, indolent course. 2. Mycosis fungoides (MF) - presents with patches and plaques preceding tumors. 3. Secondary cutaneous infiltrates of angioimmunoblastic T-cell lymphoma (AITL) - associated with Epstein-Barr virus and B symptoms. 4. Lupus erythematosus (tumidus type) - characterized by vacuolization at the hair follicle epithelium.
What laboratory findings are associated with T-cell pseudolymphoma?
Histological findings include dense nodular infiltrate extending throughout the entire dermis, rare germinal centers and granuloma formation, exocytosis of T lymphocytes into the hair follicle epithelium, and no significant exocytosis of lymphocytes into the overlying interfollicular epidermis.
What is the first-line treatment for Borrelia-associated B-cell pseudolymphoma?
The first-line treatment is antibiotics to prevent complications such as arthritis and carditis.
What is the clinical presentation of nodular T-cell pseudolymphoma?
Nodular T-cell pseudolymphoma presents with solitary or multiple red to violaceous nodules, often with a dense dermal T-cell–rich infiltrate.
What are the histological features of CD30+ T-cell pseudolymphoma?
Histological features include medium-sized to large CD30+ blast-like cells scattered throughout a T-cell–rich infiltrate.