October 2017 Case

Michelle Don, MD (Resident) and Qin Huang, MD (Faculty)

A 53-year-old female with longstanding mild anemia was found to have a solitary 0.5 cm papule on her right shoulder that had persisted for 2 months. No other suspicious cutaneous lesions were identified and the remainder of her clinical exam was unremarkable. After a month of treatment with topical creams, and no improvement in the lesion, a punch biopsy was performed.

T-cell receptor β-gene and γ-gene rearrangement positive.

Overall, the findings are most consistent with involvement by a peripheral T-cell lymphoma with characteristic features of Primary Cutaneous Small/Medium CD4 Positive T-Cell Lymphoma (PC-SMTCL).

PC-SMTCL is a type of primary cutaneous T-cell lymphoma characterized by a predominance of small to medium sized CD4-positive pleomorphic T-cells. There should be no evidence of any lesion typical of mycosis fungoides. Most cases present with a solitary skin lesion and the patient is otherwise asymptomatic. The biopsy often shows a dense dermal infiltrate of pleomorphic atypical T-cells that tend to infiltrate into the subcutaneous tissue. Epidermotropism should be mostly absent. The atypical cells express CD3 and CD4 and are without expression of CD8 and CD30. There is commonly a CD20 B-cell population and admixed plasma cells present. This entity was classified as a provisional entity in the 2008 WHO classification of lymphoid neoplasms and has since been further studied. The cells are now known to have a follicular T-cell phenotype with expression of PD1, ICOS, CXCL13, BCL-6, and CD10 at varying degrees. Although clonal rearrangements of TCR genes are seen, the 2016 revision of the WHO classification of lymphoid neoplasms refers to this entity as likely not meeting criteria for classification as a malignancy, but rather a clonal response to a stimulus that is not known. The terminology that should now be used is primary cutaneous CD4 positive small/medium T-cell lymphoproliferative disorder. The prognosis remains excellent.

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