Secondary cutaneous involvement in peripheral T-cell lymphoma: Diagnostic frameworks, staging integration, and therapeutic implications.

The occurrence of secondary cutaneous manifestations in peripheral T-cell lymphoma (PTCL) is relatively infrequent and can resemble benign dermatoses, leading to diagnosis delays. We present the case of a 78-year-old female patient with a diagnosis of PTCL affecting the left parotid gland, who experienced a 2-day sudden and intensely pruritic skin eruption, which progressed from both forearms to the trunk, involving more than 50% of the total body surface area. Initially, the eruption was managed as a hypersensitivity reaction with antihistamines and corticosteroids, with temporary symptomatic relief; however, the rapid clinical progression in the context of an established diagnosis of PTCL raised suspicion of secondary cutaneous involvement. Previous pathological examinations indicated a mature T-cell phenotype (CD2+/CD3+/CD5+/TCRβF1+), partial expression of CD4, loss of CD7 in larger cells, minimal CD30 expression (10%), and a high proliferative index (Ki-67 70%). Imaging studies demonstrated persistent disease in the parotid gland and partially necrotic cervical lymph nodes, without evidence of distant metastasis. Considering significant cardiac comorbidities and CD30 expression, an anthracycline-sparing, CD30-targeted therapeutic approach was chosen. Treatment with brentuximab vedotin yielded early alleviation of pruritus and progressive resolution of lesions by the third cycle, with favorable tolerability. This case serves as a foundation for a narrative review that underscores the diagnostic challenges associated with "allergic-appearing" eruptions in patients with T-cell lymphoma, the importance of integrated staging utilizing TNMB (skin/blood) in conjunction with Lugano/Deauville positron emission tomography-computed tomography to assess systemic burden and therapeutic response, and biologically informed systemic therapy options aligned with comorbidities, including emerging targeted treatment strategies.