[Accuracy of intraoperative diagnosis in central nervous system tumors: report of 1315 cases]

Clinicians order neurosurgery frozen sections in order to answer three questions: is the specimen tumor tissue? is it benign or malignant? what is its histological type? We studied the diagnostic accuracy of 1 315 frozen sections of central nervous system tumors, performed between 1988 and 1999, and compared it with data in the literature. Agreement between intraoperative and paraffin-section diagnosis was 96.6% (rate of error: 3.4% for the question tumor tissue or not). The answer was concordant in 92.6% with a 7.4% rate of error for tumor malignancy or benignity. Exact histological concordance was 87.6%. The most frequent errors in histological typing concerned gliomas, hemangioblastomas and metastasis. Our results emphazise the reliability of intraoperative frozen sections in Neurosurgery and the importance of close collaboration between clinicians, radiologists and pathologists.

[Benign granular cell anal tumor]

INTRODUCTION

Granular cell tumors (GCT) are rarely located in the perianal area.

OBSERVATION

Over the past 3 years, a 56 year-old man presented a papule of the right margin of the anus that had progressively increased in size (1.5 cm). Cell proliferation was located in the dermis and strongly expressed the S100 protein. It was covered by a pseudo-epitheliomatous hyperplasia of the overlying epidermis. Forty months after local surgical excision, there was no sign of recurrence.

COMMENTS

Granular cell tumors are rare and usually benign. When cutaneous or mucosal, the pseudo-epitheliomatous hyperplasia of the overlying epithelium may, on superficial samples, be mistakenly diagnosed as squamous cell carcinomas. Malignant GCT may, histologically, appear identical to a benign GCT and only the appearance of metastases (generally after local recurrence) permits the subsequent diagnosis of malignancy.