Benign nevus cell aggregates in the thymus: A case report

John R. Parker, Jae Ro, Nelson G. Ordóñez

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Aggregates of benign nevus cells occurring in lymph nodes are a well- described incidental finding. Nevus cell aggregates (NCAs) can mimic foci of metastatic carcinoma or other disease processes, so the surgical pathologist should be familiar with this lesion. The purpose of this report is to describe the potential diagnostic difficulties created by benign NCAs within the thymus of a 32-year-old man with dysplastic nevus syndrome and malignant melanoma involving mediastinal lymph nodes and the right lung. Morphologically, the NCAs in this case elicited the differential diagnoses of metastatic melanoma and thymoma. Immunohistochemical studies helped to establish the correct diagnosis by demonstrating reactivity for S-100 protein and negative staining for keratin and HMB-45. Unlike malignant melanomas, NCAs show no p53 protein immunoreactivity, and low proliferative activity was detected by Ki-67 antigen immunostaining. Although melanocytic cells were rarely reported in thymic neoplasms, we are not aware of any previous reports of NCAs occurring in the normal thymus.

Original languageEnglish (US)
Pages (from-to)329-332
Number of pages4
JournalModern Pathology
Issue number3
StatePublished - Mar 1 1999


  • Lymph node
  • Melanoma
  • Nevus cell aggregates
  • Thymoma
  • Thymus

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


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