• Be male 0-17 years of age

• Meet at least one of the following four conditions:

‣ Be scheduled to undergo surgery, chemotherapy, drug treatment and/or radiation for the treatment or prevention of a medical condition or malignancy with risk of causing permanent and complete loss of subsequent testicular function. Risk categories based on treatment regimens are indicated below. Investigators will utilize three sources to calculate risk: 1. Fertile Hope - Risks of Azoospermia brochure that details typical agents and treatment regimens in each risk category, 2. The Summed Alkylating Agent dose score (Green et al., 2009) or 3. The Cyclophosphamide Equivalent Dose method (Green et al., 2014). Because of the complexity of many treatment regimens, patient risk categorization will be at the discretion of the investigators.

• High Risk

‣ \>= 80% risk of prolonged azoospermia, Fertile Hope Brochure

⁃ Summed alkylating agent dose score \>= 3

⁃ Cyclophosphamide equivalent dose \>= 7,500mg/m\^2

∙ Intermediate risk (21-79% risk of prolonged azoospermia, Fertile Hope)

∙ Low Risk ( =\< 20% risk of prolonged azoospermia, Fertile Hope)

∙ Eligibility is limited to patients in the High risk category and/or intermediate risk after discussion with pediatric oncology, fertility preservation team, and the patient/family

⁃ Or, have a medical condition or malignancy that requires removal of all or part of one or both testicles

⁃ Or, have a medical condition (genetic or autoimmune) that results in decline in fertility (e.g. Klinefelter syndrome)

⁃ Or, have a newly diagnosed or recurrent disease affecting fertility. Those who were not enrolled at the time of initial diagnosis (i.e. patients with recurrent disease) are eligible if they have not previous received therapy that is viewed as likely to result in complete and permanent loss of testicular function

• Have two testicles if undergoing elective removal of a testicle for fertility preservation only. Note: removal of both testicles will limit fertility preservation options. Or have 1 testicle but limited potential for future fertility due to underlying condition, malignancy, prior surgery or previous torsion and no other fertility preservation methods are available except for testicular tissue cryopreservation

• Sign an approved informed consent and authorization permitting the release of personal health information. The patient and/or the patient's legally authorized guardian must acknowledge in writing that consent for specimen collection has been obtained, in accordance with institutional policies approved by the United States (U.S.) Department of Health and Human Services

• Consent for serum screening tests for infectious diseases to be performed at the time of testicular tissue harvesting. The immediate testing will include but not be limited to testing for Hepatitis B, Hepatitis C, and human immunodeficiency virus (HIV)

• Undergo a full history and physical examination and obtain standard pre-operative clearance (based on the most recent American College of Cardiology/ American Heart Association \[ACC/AHA\] Guideline for Perioperative Cardiovascular Evaluation for Noncardiac Surgery) as determined by their primary surgeon

• Note: In cases of torsion of testicles or other medical conditions that result in impairment of testicular function, patients can be consented and included in the study, if during the testicular surgery the provider finds that the patient still has viable tissue that can be cryopreserved.