Distribution and estimation of nucleolar organizer regions in various human lung tumours.

A quantitative study of nucleolar organizer regions in human lung carcinomas was carried out on routinely processed paraffin embedded tissue sections. We examined 104 lung carcinomas including 38 squamous cell carcinomas, 36 adenocarcinomas, 18 large cell anaplastic carcinomas, 6 small cell carcinomas and 6 carcinoids. No significant differences were found in mean number of NORs between squamous, adenocarcinoma and undifferentiated carcinomas including large cell and small cell carcinomas. Carcinoids had comparatively lower means except for one typical carcinoid. Considering the high incidence of overlap between ranges of NOR counts in these groups of tumours and in agreement with the only other study of lung tumours (which comprised only carcinoids and small cell carcinomas), we conclude that this technique cannot be reliably used to discriminate between various histologic types of lung cancers. However, long term follow up of these patients is needed to establish the value of the AgNOR technique for prognostic guidance.