Inclusion Criteria:

• * Written informed consent
• * Adequate fresh or archival tumor biopsy or intent to obtain fresh tumor biopsy.
• * Pathologically-confirmed mature T- or natural killer (NK)-cell lymphoma meeting one of the following diagnostic criterion (based on WHO classification and NCCN guidelines):
• * T-cell prolymphocytic leukemia
• * T-cell large granular lymphocytic leukemia
• * Chronic lymphoproliferative disorder of NK cells
• * Aggressive NK-cell leukemia
• * Systemic Epstein-Barr virus (EBV)-positive T-cell lymphoma of childhood
• * Chronic active EBV infection of T- and NK-cell type, systemic form
• * Hydroa vacciniforme-like lymphoproliferative disorder
• * Adult T-cell leukemia/lymphoma
• * Extranodal NK/T-cell lymphoma, nasal type
• * Enteropathy-associated T-cell lymphoma
• * Monomorphic epitheliotropic intestinal T-cell lymphoma
• * Intestinal T-cell lymphoma, not otherwise specified (NOS)
• * Indolent T-cell lymphoproliferative disorder of the gastrointestinal tract
• * Hepatosplenic T-cell lymphoma
• * Subcutaneous panniculitis-like T-cell lymphoma
• * Mycosis fungoides (limited to those with ≥ stage IB disease and those receiving active therapy)
• * Sézary syndrome
• * Primary cutaneous anaplastic large cell lymphoma (receiving systemic therapy)
• * Primary cutaneous Gamma-Delta T-cell lymphoma
• * Primary cutaneous CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma
• * Primary cutaneous acral CD8+ T-cell lymphoma (receiving systemic therapy)
• * Peripheral T-cell lymphoma, not otherwise specified
• * Angioimmunoblastic T-cell lymphoma
• * Follicular T-cell lymphoma
• * Nodal peripheral T-cell lymphoma with TFH phenotype
• * Anaplastic large cell lymphoma, ALK-positive
• * Anaplastic large cell lymphoma, ALK-negative
• * Breast-implant associated anaplastic large cell lymphoma.
• * NOTE: Patients with diagnoses of mycosis fungoides, primary cutaneous anaplastic large cell lymphoma, and/or primary cutaneous acral CD8+ T-cell lymphoma must be receiving systemic therapy.

Exclusion Criteria:

• * Patients with of mycosis fungoides, primary cutaneous anaplastic large cell lymphoma, and/or primary cutaneous acral CD8+ T-cell lymphoma not receiving systemic therapy.
• * Inability to collect prospective data, measure response, or perform adequate follow-up assessments in the clinical judgment of the treating physician. NOTE: Repository participation does not exclude participation in clinical trials, nor does existing clinical trial participation exclude enrollment in the study herein outlined.