Primary cutaneous B-cell lymphoma—leg type in a young adult
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Primary cutaneous B-cell lymphomas-leg type (PCBCL-L) usually present in elderly female patients, and with a pathophysiology poorly understood its possible origin is most likely multifactorial involving genes from chronic antigen stimulation from viral or bacterial infections.

A 45-year-old male presented with past medical history of (HIV) for 9 years on highly active antiretroviral therapy, type 2 diabetes mellitus and essential hypertension, with ongoing right lower extremity pain for the last 4 months. Four days before hospital admission, the patient noticed new ulcerations on his right lower extremity, associated with increased swelling and subjective febrile episodes. Initially, he was diagnosed with cellulitis, warranting surgical debridement and antibiotic therapy with doxycycline. His condition was stable on discharge, however, his symptoms worsened, and he was readmitted after 12 days.

A thorough physical examination also revealed a new scaling and raised erythematous indurated lesions on his left lower extremity. Patient underwent a second wound debridement and a tissue sample for biopsy was obtained. Skin biopsy showed histological findings consistent with diffuse large B-cell lymphoma.

His right lower extremity, however, became progressively more swollen, painful and with worsening ulcerations and he was readmitted. During his second hospital admission, (CT) of the right lower extremity revealed images concerning for myositis. He was started on broad spectrum antibiotics with vancomycin, meropenem and clindamycin. Surgery and interventional radiology were consulted; they recommended against acute surgical intervention. Before initiation of chemotherapy by the oncology service, he underwent cancer staging with CT of the head, chest, abdomen and pelvis.

Prophylactic methotrexate was administered intrathecally due to the disease’s high risk of CNS involvement. PET/CT scan showed extensive and diffuse subcutaneous indurations with associated hypermetabolic activity involving the right lower extremity, supporting the absence of any neoplastic extension. He started chemotherapy as inpatient with a regimen consisting of a combination of R-CHOP. Within the next few months, his skin wound decreased in size along with symptomatic improvement.

Approximately 3–4 weeks later, CT scans showed there was near complete interval resolution of tissue edema, decreased caliber of reactive right inguinal and pelvic sidewall lymph nodes and no new lymphadenopathy. The decision was to pursue treatment with R-CHOP chemotherapy and intrathecal methotrexate for 5 cycles with excellent response initially, but after his fifth cycle, patient was found to have significant progression of cutaneous lesions.