Patient description: The patient is a 41-year-old man and a known case of Acromegaly who underwent transsphenoidal surgery 4 months ago. He came to the clinic for the follow up lab studies after his primary resection surgery. His lab study shows the IGF-1 level of 4.5 ULN adjusted by sex and age. His random GH level is 4 ug/L. The recent brain MRI confirmed the residual pituitary tumor. His past medical history is only significant for acromegaly due to pituitary adenoma and the recent surgery. After his surgery he takes only vitamin D and multivitamins.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Ductal Breast Carcinoma In Situ Estrogen Receptor Positive Screen-detected, estrogen receptor (ER) positive DCIS of the breast proven on core needle biopsy, defined as 10% positive cells; the presence of a focus suspicious for microinvasion will be allowed; the size of the DCIS in the core biopsy sample must total 5 mm (multiple cores can be summed) and must be estimated on the deepest step section (if step sections are taken) Eastern Cooperative Oncology Group (ECOG) performance status =< 1 (Karnofsky >= 70%) Participants must have acceptable organ and marrow function as defined below: Baseline lab parameters are not standard of care for initiation of tamoxifen therapy; a minimal panel will therefore be appropriate Leukocytes >= 3,000/microliter Absolute neutrophil count >= 1,500/microliter Platelets >= 100,000/microliter Total bilirubin within "≤1.5 x institutional upper limit of normal (ULN)institutional limits Aspartate aminotransferase (AST) (serum glutamic-oxaloacetic transaminase [SGOT])/alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT]) =< 1.5 x institutional upper limit of normal (ULN) Creatinine within "≤1.5 x institutional upper limit of normal (ULN) institutional limits Women of childbearing potential and their male partners must agree to use TWO effective forms of birth control (abstinence is not an allowed method) prior to study entry and for the duration of study participation, and for two months following the last dose of study medications; effective birth control methods are: copper IUD [intrauterine device], diaphragm/cervical cap/shield, spermicide, contraceptive sponge, condoms; women of childbearing potential must have a negative urine pregnancy test within seven days before starting study medications; should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her study physician immediately  DCIS presentation as a palpable mass Exogenous sex steroid use within 4 weeks prior to core needle biopsy Prior ipsilateral breast cancer radiotherapy will be excluded; prior contralateral breast cancer therapy within 2 years will also be excluded Skin lesions on the breast that disrupt the stratum corneum (eg eczema, ulceration) History of endometrial neoplasia History of thromboembolic disease (history of varicose veins and superficial phlebitis is allowed) Current smokers Current users of potent inhibitors of tamoxifen metabolism must be able to discontinue their use and switch to an alternative medication for the duration of participation, under the advice of their physician; if the physician feels that an alternative medication is not appropriate for the subject and the current medication is medically necessary, the subject will not be eligible; the drugs are listed below; many of these are not in clinical use at the moment; bupropion, celecoxib, chlorpheniramine, chlorpromazine, cimetidine, citalopram, clemastine, clomipramine, clozapine, cocaine, delavirdine, desipramine, diphenhydramine, doxepin, duloxetine, escitalopram, fluoxetine, haloperidol, halofantrine, hydroxyzine, imipramine, isoniazid, ketoconazole, methadone, methimazole, mibefradil, miconazole, nicardipine, paroxetine, pergolide, perphenazine, pioglitazone, pyrimethamine, quinidine, quinine, ranitidine, ritonavir, ropinirole, sertraline, terbinafine, thioridazine, ticlopidine, tranylcypromine, trazodone, tripelennamine Prior use of SERMS or AIs including tamoxifen, raloxifene, anastrozole, letrozole, or exemestane for prevention or therapy within 5 years Participants may not be receiving any other investigational agents within 30 days of enrollment or during this study