Pseudolymphomas
Last Updated: 2023-07-07
Author(s): Anzengruber F., Navarini A.
ICD11: 4A43.0
Last Updated: 2023-07-07
Author(s): Anzengruber F., Navarini A.
ICD11: 4A43.0
Pseudolymphoma, Cutaneous pseudolymphoma,
Benign lymphocytic proliferation of the skin that can clinically and histologically mimic malignant lymphoma.
Distinguishing between B- and T-cell pseudolymphomas is done using immunophenotyping.
Important distinction between benign and malignant entity is characterised by clinic and course of disease.
1. B-cell pseudolymphomas (lymphadenosis cutis benigna, cutaneous inflammatory pseudotumour)
2. Combined B- and T-cell pseudolymphomas (lymphocytic drug reaction)
3. T-cell pseudolymphomas (actinic reticuloid, lymphomatoid contact dermatitis, lymphocytic infiltration of the skin, acral pseudolymphomatous angiokeratoma- APACHE)
4. Unclassifiable pseudolymphomas
Morphological criteria for assignment to entity are variable, e.g. malignant lymphomas may extend deeper into the tissue and have a monomorphic infiltrate. Reactive germinal centres are more likely to be found in pseudolymphomas (lymphocytoma). Furthermore, a loss of pan-T-cell antigens such as CD2, CD3 and betaF1 can be recognised in malignant lymphomas. CAVE: one must differentiate follicular lymphoma and cutaneous marginal zone B lymphoma of the MALT type.
There are various causes:
- Drug reaction: Lymphocytic drug reaction
- Arthropod reaction and idiopathic: Lymphadenosis cutis benigna
- Contact allergy: Lymphomatoid contact allergy
- Unexplained:
Single, grouped or disseminated papules, nodules or tumours. Diffuse involvement and lymphoadenopathies are more indicative of malignant lymphoma
Dense, striated, lymphohistiocytic infiltrate, cell polymorphism, epidermal and vascular involvement. Pleomorphies, hyperchromasia or mitoses may be signs of malignancy, but rarely occur.
Transition to malignant lymphoma.
Favourable (monitoring of clinical course and ensuring absence of metastasis).
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