Beyond the Rash: Cutaneous Peripheral T-Cell Lymphoma as a Diagnostic Pitfall in Primary Care.

Cutaneous manifestations of T-cell lymphomas may resemble common dermatologic or infectious conditions, increasing the risk of delayed recognition. We report a 78-year-old woman with known peripheral T-cell lymphoma (PTCL) who presented with a rapidly progressive, diffuse erythematous rash accompanied by cervical lymphadenopathy. Initial evaluation prioritized more common etiologies; however, inpatient medicine broadened the differential diagnosis, prompting early hematology and oncology consultation. Contrast-enhanced CT of the neck demonstrated multiple enlarged, partially necrotic left cervical lymph nodes consistent with disease progression. After multidisciplinary discussions and consideration of prognosis, the patient elected palliative-focused management with oncology follow-up. This case underscores the importance of emergency and primary care clinicians to include cutaneous lymphoma in the differential diagnosis of new diffuse rashes in patients with known or suspected hematologic malignancy, particularly when accompanied by lymphadenopathy or rapid progression.