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Benign nevus cell aggregates in the thymus: a case report.
J R Parker1, J Y Ro, N G Ordóñez
1Department of Pathology, Baylor College of Medicine, Houston, Texas 77030, USA.
Summary
Benign nevus cell aggregates (NCAs) in the thymus can mimic cancer. Immunohistochemistry confirmed NCAs, distinguishing them from melanoma and thymoma in this rare case.
Area of Science:
- Surgical Pathology
- Dermatopathology
- Immunohistochemistry
Background:
- Benign nevus cell aggregates (NCAs) are incidental findings in lymph nodes.
- NCAs can be mistaken for metastatic carcinoma, requiring pathologist familiarity.
- This report details diagnostic challenges posed by NCAs in the thymus.
Observation:
- A 32-year-old man with dysplastic nevus syndrome and melanoma presented with NCAs in the thymus.
- The NCAs mimicked metastatic melanoma and thymoma morphologically.
- Immunohistochemical studies were crucial for accurate diagnosis.
Findings:
- NCAs showed positive staining for S-100 protein.
- NCAs were negative for keratin and HMB-45.
- NCAs lacked p53 protein immunoreactivity and exhibited low Ki-67 proliferation, differentiating them from melanoma.
Implications:
- This case highlights the importance of immunohistochemistry in diagnosing rare thymic lesions.
- It expands the differential diagnosis for thymic pathology.
- Reports of NCAs in the normal thymus are exceptionally rare.