Malignant thymus tumour progressing into acute leukaemia with non-specific esterase activity

Area of Science:

• Oncology
• Hematology
• Pathology

Background:

• Describes a rare case of a massive mediastinal tumor in an pediatric patient.
• Highlights the initial treatment challenges including surgical non-resectability.

Observation:

• The tumor initially responded to radiation therapy and combination chemotherapy.
• Disease progression occurred three months post-treatment, with increased blasts in peripheral blood and bone marrow.
• The terminal phase presented as acute leukemia refractory to chemotherapy.

Findings:

• Blast cells from the thymic malignancy exhibited non-specific esterase activity.
• Specifically, the NaF-sensitive esterase, typically associated with monocytes-macrophages, was detected.
• However, other monocyte-macrophage markers were negative, creating an atypical profile.

Implications:

• This case suggests that NaF-sensitive naphthol-AS-acetate esterase activity is not exclusive to tumors of the monocyte-macrophage system.
• Challenges traditional diagnostic markers in hematologic and oncologic pathology.
• May necessitate re-evaluation of lineage determination in certain pediatric malignancies.