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Published on: March 17, 2013
Nonlymphoid intraepidermal mononuclear cell collections (pseudo-Pautrier abscesses): a morphologic and
E Candiago1, D Marocolo, M A Manganoni
1Department of Pathology, University of Brescia, Italy.
Insights
Intraepidermal collections of mononuclear cells (ICMC) are common in inflammatory skin conditions like spongiotic dermatitis. These cells, resembling dendritic cells, originate from monocytes and differentiate into Langerhans cells.
Area of Science:
- Dermatopathology
- Immunohistochemistry
- Cell Biology
Background:
- Intraepidermal collections of mononuclear cells (ICMC) are observed in various skin conditions.
- Their precise nature and origin in inflammatory dermatoses and lymphomas are not fully understood.
Purpose of the Study:
- To investigate the incidence, morphology, and immunophenotype of ICMC.
- To determine the association of ICMC with specific inflammatory dermatoses and cutaneous lymphomas.
Main Methods:
- Analysis of 1,248 skin biopsies from patients with inflammatory dermatoses and cutaneous lymphomas.
- Morphological assessment and immunohistochemical staining for various cell markers (CD1a, S-100, CD14, CD11b, CD36, CD68, CD83).
Main Results:
- ICMC were identified in 9.9% of biopsies, notably frequent in spongiotic dermatitis (43.4%) and lichenoid dermatitis (10%).
- Cells within ICMC expressed markers of mature Langerhans cells (CD1a, S-100) and monocyte/macrophage lineage (CD11b, CD36, CD68), with some expressing CD83.
- ICMC were also found in cutaneous T-cell lymphoma, mimicking Pautrier abscesses.
Conclusions:
- ICMC represent a frequent, yet understudied, phenomenon in dermatopathology.
- These collections are composed of dendritic cells and their precursors, likely derived from circulating monocytes and differentiating into Langerhans cells.
- ICMC are particularly prevalent in spongiosis-associated dermatoses and can be mistaken for Pautrier abscesses in cutaneous T-cell lymphoma.
Abstract:
We evaluated the incidence, morphology, and immunophenotype of intraepidermal collections of mononuclear cells (ICMC) in a large number of inflammatory dermatosis and cutaneous lymphomas. ICMC appeared as small to large aggregates of cells, showing a morphology variable from monocytes to obvious dendritic cells, admixed with rare lymphocytes. ICMC were recognized in the epidermis or within hair follicle epithelium, and were either loosely or compactly arranged. ICMC were identified in 124 of 1,248 skin biopsies (9.9%) of inflammatory or lymphoid infiltrates, and were particularly frequent in spongiotic (43.4%) and in lichenoid dermatitis (10%), whereas they were rarely found in nonspecific superficial dermatitis (3.8%) and in psoriasis (4.7%). ICMC were also frequent in cutaneous T-cell lymphoma (13.3%), where they mimicked Pautrier abscesses. The ICMC forming cells showed a unique phenotype: the majority of them expressed CD1a and S-100, and lacked CD14, similar to mature Langerhans cells, but they were also strongly labeled by anti-CD11b, anti-CD36, and anti-CD68. Moreover, a subpopulation of them expressed CD83, an antigen that is usually absent on Langerhans cells. The occurrence of ICMC is a rather frequent, although hitherto poorly studied, phenomenon, occurring in several dermatosis, but particularly frequent in spongiosis-associated skin reactions. The cells within ICMC are represented by dendritic cells and dendritic cell precursors, whose phenotype indicates their derivation from circulating monocytes and differentiation into mature Langerhans cells.
