Refractory lichen planus-like lesions reveal underlying systemic T-cell lymphoma

A 61-year-old man had a 2-year history of painful mucosal lesions and pruritic violaceous plaques on the trunk and extremities. Repeatedly diagnosed with oral lichen planus, he received prolonged topical and systemic therapies, including corticosteroids, hydroxychloroquine and herbal medicine, with minimal response and progressive worsening. Examination showed diffuse erythematous-to-violaceous scaly patches and plaques on the trunk and limbs, hyperkeratotic plaques on the dorsal hands with nail thickening and longitudinal ridging, severe erosions and hemorrhagic crusting of the lips, Wickham striae on the buccal mucosa, and genital erythema with mild exudation.

Skin biopsies from the lip and left hand showed lichenoid lymphocytic infiltration with basal vacuolar degeneration and pigment incontinence, supporting lichen planus; direct immunofluorescence was not performed. PET-CT showed multiple lymph nodes with increased FDG uptake. Flow cytometry detected aberrant T-cell populations in peripheral blood and bone marrow; lymph node flow cytometry showed aberrant T lymphocytes accounting for 91.72% of lymphocytes. Lymph node biopsy showed atypical lymphoid hyperplasia with vascular invasion, a predominantly CD4-positive T-cell infiltrate with scattered CD8-positive cells, T-cell receptor gene rearrangement clonality, and negative EBER. The final diagnosis was systemic peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), with extensive lichen planus-like mucocutaneous disease.

The biopsied skin lesions showed lichenoid/interface dermatitis without atypical lymphoid infiltrates, prominent epidermotropism or dense dermal tumor infiltrates, so lymphoma-directed testing was not pursued on skin specimens. Chronic oral involvement, Wickham striae, nail changes and lichenoid histopathology supported lichen planus-like disease, but the unusually extensive distribution, poor response to conventional therapy and systemic lymphadenopathy prompted further evaluation that led to PTCL-NOS. Lichenoid drug eruption was less likely because there was no clear temporal relationship with a new medication. Paraneoplastic pemphigus and other autoimmune blistering diseases were not favored given negative indirect immunofluorescence and blistering serology and absence of acantholysis, although direct immunofluorescence was not performed.

Connective tissue disease was not supported by serologic testing or histopathology. The patient was treated with combination chemotherapy and supportive dermatologic care; his cutaneous plaques and oral erosions improved substantially. The authors highlight that presumed lichen planus-like disease that is unusually extensive or multisite, progressive and refractory to appropriate therapy, or accompanied by lymphadenopathy should prompt evaluation for an underlying malignancy; imaging, lymph node biopsy, bone marrow assessment, clinicopathologic correlation and multidisciplinary collaboration are important.