Male Breast Cancer Complicated With Leukocytosis Resembling Leukemia Reaction After Chemotherapy: A Case Report

Abstract

Introduction: Male breast cancer (MBC) accounts for less than 1% of all cancers in men, with invasive ductal carcinoma being the most common type. The chemotherapy regimens used for MBC are similar to those for female breast cancer. However, the incidence of chemotherapy-induced complications such as leukocytosis resembling leukemia reaction is not well documented in MBC. This case highlights a rare complication in an MBC patient, induced by prophylactic PEG-rhG-CSF following chemotherapy.

Case presentation: A 51-year-old male with left breast invasive ductal carcinoma underwent modified radical mastectomy. Postoperative pathology revealed high-risk features, and the patient received 8 cycles of chemotherapy with the ddAC-T regimen, followed by PEG-rhG-CSF for febrile neutropenia prevention. After the fifth chemotherapy cycle, the patient developed leukocytosis resembling leukemia reaction, characterized by a white blood cell count exceeding 50 × 10⁹/L, along with intermittent fever up to 42.5°C. The condition was attributed to the PEG-rhG-CSF administration, and the patient was treated with NSAIDs and dexamethasone. Leukocytosis resolved after adjusting the PEG-rhG-CSF dose.

Conclusion: Leukocytosis resembling leukemia reaction induced by PEG-rhG-CSF post-chemotherapy is a rare complication, particularly in MBC patients. This case underscores the importance of careful monitoring and differential diagnosis to avoid misdiagnosis and unnecessary interventions. Personalized treatment strategies and dose adjustments for PEG-rhG-CSF are crucial in managing this rare reaction, emphasizing the need for awareness and individualized care in MBC patients undergoing chemotherapy.

Keywords: chemotherapy; leukocytosis resembling leukemia reaction; male breast cancer.

FIGURE 1

Breast ultrasonography showing a hypoechoic nodule measuring 13 × 13 × 8 mm with clear boundaries, irregular shape, and inhomogeneous internal echo located beneath the left nipple.

FIGURE 2

Changes in leukocytes and ANCs over 8 chemotherapy cycles. ANC, absolute neutrophil count. (The 50‐year‐old male patient received the AC‐T chemotherapy regimen for 8 cycles [Cycle A to Cycle H]. He was instructed to receive a subcutaneous injection of Mecapegfilgrastim [a long‐acting PEG‐rhG‐CSF] 6 mg within 48 h after chemotherapy. He rechecked his hematological analysis on the 7th and 13th days after each chemotherapy session to monitor changes in leukocytes and ANCs over 8 chemotherapy cycles). ANC, absolute neutrophil count. *Normal values of leukocyte, ANC counts: 3.5–9.5 × 10⁹/L (Leukocytes); 1.4–7.2 × 10⁹/L (ANCs).

FIGURE 3

The progress of the patient's treatment. AR, androgen receptor; BC, breast cancer; CRP, C‐reactive protein; ER, estrogen receptor; FISH, fluorescence in situ hybridization; HER2, human epidermal growth factor receptor 2; HR, hormone receptor; MDT, multidisciplinary treatment; NSAIDs, nonsteroidal antiinflammatory drugs; PR, progesterone receptor. ddAC‐T: dd, Dose‐Dense (q2w); A, Doxorubicin; C, Cyclophosphamide; T, Paclitaxel.

FIGURE 4

Changes in temperature, leukocytes, ANCs, and CRP following the fifth chemotherapy cycle. ANC, absolute neutrophil count; CRP, C‐reactive protein. Color conventions follow standard hematologic parameter representations in clinical studies. *Normal values of leukocyte, ANC, CRP counts: 3.5–9.5 × 10⁹/L (Leukocytes); 1.4–7.2 × 10⁹/L (ANCs); 0–5.00 mg/L (CRP).

FIGURE 5

Leukemoid reaction process flow diagram.