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Lymphomatoid papulosis with CD1a+ dendritic cell hyperplasia, mimicking Langerhans cell histiocytosis
Chris H Jokinen1, Gregory M Wolgamot, Brent L Wood
1Department of Pathology, University of Washington, Seattle, WA 98195, USA.
Insights
This case study highlights a rare instance where abundant dendritic cells (DCs) mimicked Langerhans cell histiocytosis, masking an underlying lymphoproliferative disorder in skin biopsies.
Area of Science:
- Dermatopathology
- Immunohistochemistry
- T-cell Lymphoma
Background:
- Cutaneous T-cell lymphomas (CTCL) often feature CD1a+ dendritic cells (DCs).
- A high density of DCs in skin biopsies can complicate diagnosis.
- Distinguishing between reactive and neoplastic lymphoid infiltrates is crucial.
Observation:
- A 70-year-old man presented with lesions initially diagnosed as Langerhans cell histiocytosis.
- Skin biopsies revealed a dual population of epithelioid cells (CD1a+, S-100+) and atypical lymphocytes (CD30+, CD3+, CD5+).
- T-cell receptor gene rearrangement confirmed a clonal T-cell population.
Findings:
- This case presents an unusually florid proliferation of dendritic cells (DCs).
- The DC proliferation mimicked Langerhans cell histiocytosis.
- The findings masked an underlying lymphoproliferative disorder, specifically lymphomatoid papulosis.
Implications:
- This report is the first to describe a florid DC proliferation mimicking Langerhans cell histiocytosis in the context of lymphomatoid papulosis.
- Recognizing this unusual presentation is vital for accurate diagnosis of cutaneous lymphomas.
- Enhanced diagnostic criteria may be needed for complex skin infiltrates.
Abstract:
Although CD1a+ dendritic cells (DC) in cutaneous T-cell lymphomas (CTCL) have been well documented, the presence of large numbers of DC within lymphoid infiltrates can pose a diagnostic difficulty. We present a case of a 70-year-old man with a 3-year history of recurrent red papules and plaques on the extremities and trunk that was referred to our institution, with the diagnosis of Langerhans cell histiocytosis. Skin biopsies showed a wedge-shaped cellular infiltrate in the superficial and deep dermis consisting of two cell populations. Most prominent were clusters of epithelioid cells with grooved nuclei and abundant eosinophilic cytoplasm, which stained with antibodies to CD1a and S-100. A second, less prominent population of atypical lymphocytes, some with enlarged, hyperchromatic and convoluted nuclei, were intermixed. The latter were positive for CD30, CD3 and CD5 and negative for CD20, CD34, CD68, ALK-1 and TdT. T-cell receptor gene rearrangement studies confirmed a clonal T-cell population, which with the clinical history was consistent with the diagnosis of lymphomatoid papulosis. While previous studies have shown an increased density of dermal DC in CTCL, we believe that this represents the first report of an unusually florid DC proliferation mimicking Langerhans cell histiocytosis and masking a lymphoproliferative disorder.