Pustulo-ovoid bodies of Milian in granular cell tumors.

Background: Granular cell tumors (GCTs) are benign neural tumors with a distinct histologic appearance on light microscopy, characterized by eosinophilic cytoplasmic granules. Pustulo-ovoid bodies of Milian (POB) are larger granules surrounded by a clear halo. There have been no histologic studies to document their prevalence in GCT.

Methods: We examined the sections of 47 cases of GCT stained with hematoxylin and eosin to determine the frequency of POB within this tumor. POB were measured per 10 high-power fields (HPFs) and were divided into the following categories: less than 10 POB per 10 HPFs, 10-30 per 10 HPFs, 30-50 per 10 HPFs and greater than 50 per 10 HPFs.

Results: POB were present in 100% of the specimens examined. Eleven cases (23%) had between 1 and 9 POBs per 10 HPFs, twelve cases (26%) had between 10 and 29 POBs per HPFs, five cases (11%) had between 30 and 50 POBs per HPFs and nineteen cases (40%) had greater than 50 POBs per HPFs. When grouped according to clinical characteristics, there was an even distribution of POB by age, sex and site of the tumor.

Conclusions: In our series, POB were present in varying numbers in all the tumors studied. They appear to represent the heterogeneity of the lysosomes, giving the appearance of large granules that have partially detached from the adjacent cytoplasm. POB are an easily recognizable component of GCTs.