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- Presentation
Understanding Atypical Lymphocytic Infiltrates in Dermatopathology
Description
The speaker explains that an atypical lymphocytic infiltrate is a common dermatopathology dilemma that often causes patient anxiety because the term sounds ominous even though it does not automatically mean cancer. The goal of the talk is to help clinicians understand how dermatopathologists think about these biopsies: atypia may reflect reactive, benign, or malignant processes, and many cases require correlation with clinical findings rather than pathology alone. The presentation reviews pseudolymphomas and several mimickers of lymphoma, including tattoo reactions, dense dermal lymphoid infiltrates, primary cutaneous CD4-positive small/medium lymphoproliferative disorder, medication-related epidermotropic infiltrates, acute EBV-related eruptions that look frankly malignant, chronic actinic dermatitis, and keratoacanthoma with associated atypical infiltrate in a patient with prior myelodysplasia. The talk also highlights newer tools such as TOX1, TRBC1, and PD-1 that can help distinguish benign from malignant T-cell processes, especially in mycosis fungoides and Sézary syndrome. The main takeaway is that most atypical lymphoid infiltrates are ultimately benign or non-progressive, but proper interpretation depends on lesion number, clinical context, clonality, and available ancillary studies; only rarely does an atypical infiltrate prove malignant.
View moreConclusions
- Most atypical lymphocytic infiltrates in skin are ultimately benign or reactive rather than malignant.
- Clinicopathologic correlation is essential because histology alone often cannot reliably distinguish lymphoma from pseudolymphoma or inflammatory mimics.
- Single, self-limited lesions without convincing clonality or progression generally favor a reactive diagnosis.
- Many dramatic-looking infiltrates are caused by specific benign triggers such as tattoos, drugs, infections, or chronic inflammatory dermatoses.
- Some entities now classified as cutaneous lymphoproliferative disorders may look worrisome histologically but usually do not behave aggressively.
- Ancillary markers such as TOX1, PD-1, and TRBC1 can help separate reactive from malignant T-cell infiltrates.
- TRBC1 appears especially useful as a practical marker of T-cell clonality with high predictive value.
- Mycosis fungoides and Sézary syndrome require integration of clinical pattern, pathology, and immunophenotype rather than relying on atypia alone.
- Several classic lymphoma mimics, including acute EBV infection and chronic actinic dermatitis, can produce highly atypical epidermotropic lymphoid infiltrates.
- The overall message is to avoid overcalling malignancy when the clinical context and additional testing support a benign or reactive process.
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