Unexpected thrombocytopenia of a rare tamoxifen-induced complication in breast cancer therapy: A case report

Table 1 Timeline of key clinical events

Month	Event	Clinical findings	Interventions	Outcomes
0	Symptom onset	Left breast lump (4 cm × 4 cm), painless, progressive	None	Patient delayed seeking care
4	Diagnosis and surgery	BIRADS 5 Lesion, invasive ductal carcinoma (cT2N0M0, ER/PR+, HER2-)	Left modified radical mastectomy	Histopathology: PT2N0Mx, no invasion; uneventful recovery
5	Post-surgery	No complications	None (lost to follow-up)	Adjuvant therapy delayed
17	Restaging and treatment start	No recurrence; anemia (hemoglobin: 7.1 g/dL, platelets: 159000/μL)	Parenteral iron, tamoxifen 20 mg/day	Anemia corrected; tamoxifen initiated
18	Thrombocytopenia	Grade III thrombocytopenia (platelets: 43000/μL), no bleeding	Tamoxifen withheld; diagnostic workup	Platelets normalized (165000/μL) in 3 weeks
19	Rechallenge	Recurrent thrombocytopenia (platelets: 77000/μL)	Tamoxifen permanently discontinued	Thrombocytopenia confirmed as tamoxifen-related
20	Follow-up	Normal CBC (platelets: 165000/μL), asymptomatic	Referral for alternative ET	Patient stable, satisfied with care

Chronological summary of the patient’s clinical course, highlighting diagnosis, treatment, adverse events, and outcomes. BIRADS: Breast Imaging Report and Data System; CBC: Complete blood count; ER: Estrogen receptor; ET: Essential thrombocythemia; HER2: Human epidermal growth factor receptor 2; PR: Progesterone receptor.