Nucleolar organizer region staining patterns in paraffin-embedded tissue cells from human skin cancers Rosana F. Roma ˜ o-Corre ˆa 1 , Durvanei A. Maria*, Mithitaka Soma 2 , Mı ´rian N. Sotto 3 , Jose ´ Anto ˆnio Sanches Jr 3 , Cyro Festa Neto 3 and Itamar R. G. Ruiz 1 1 Genetics Laboratory, 2 Herpetology Laboratory, Butantan Institute, and 3 Dermatology Department, School of Medicine, University of Sa ˜ o Paulo and Clinics Hospital, Sa ˜ o Paulo, SP, Brazil Dr Itamar R. Garcia Ruiz, Genetics Laboratory, Butantan Institute, CEP 05503-900, Av. Vital Brazil 1500, Sa ˜ o Paulo, SP, Brazil e-mail: itamruiz@usp.br Accepted for publication October 5, 2004 Background: Increased number of nucleoli (nucleolar organizer regions, NORs) with abnormal shapes and sizes, including small dots, has been used as prognostic tools to evaluate tumor proliferation levels and troublesome borderline lesions. In this study, NOR patterns of skin cancers were performed in the search of a valuable prognostic method to complement other histological procedures. Methods: Paraffin-embedded tumor tissue was obtained from basal and squamous cell carcinomas, cutaneous malignant melanoma, premalignant lesions, and Skmel-28 human melanoma cells. Slices were dewaxed and AgNOR stained. The patterns were scored and submitted for statistical analyses. Results: All types of cancer cells showed variable numbers of abnormally shaped nucleoli and dot-like structures. Only tumor cells presented four or more nucleoli, with or without dots, while 85% of the normal cells had one single NOR without dots. Most data were statistically significant when compared to normal cells. As a whole, squamous cell carcinoma and malignant melanoma tumor cells had less NOR alterations than basal cell carcinoma (BCC) tumor types. Conclusions: Changes in the number and shape of nucleoli present in malignant cells could be attributed to increased levels on rDNA transcription on cancer cells, besides abnormal remodeling of chromatin, which could disrupt proper nucleoli association. Increased genetic alterations on malignant basal cells could contribute to impair invasive and migration abilities of BCC tumors. Roma ˜ o-Corre ˆa RF, Maria DA, Soma M, Sotto MN, Sanches JA, Neto CF, Ruiz IRG. Nucleolar organizer region staining patterns in paraffin- embedded tissue cells from human skin cancers. J Cutan Pathol 2005; 32: 323–328. # Blackwell Munksgaard 2005. Three types of solid human skin cancers are currently described: basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and malignant melanoma (MM). These tumors arise from epidermal basal cells, squa- mous cells, and melanocytes, respectively, showing different biological behavior concerning metastasis potential. BCC tumors may be grouped according to the degree of histopathological aggressivity as superficial multicentric, solid, adenoid or cystic, and sclerosing. 1 SCC and MM tumors develop in situ and may present several invasive grades. Nucleolar organizer regions (NORs) are composed of chromosomal sites endowed with ribosomal DNA (rDNA), transiently clustered in order to synthesize ribosomal RNAs (rRNA). rRNAs are the main con- stitutive elements of ribosomes, responsible for all protein synthesis in the cell. Silver-staining techniques have been developed to reveal NOR sites in meta- phase chromosomes and interphase nuclei based on the detection of ribosomal proteins, nucleolin, and *Present address: Biochemistry and Biophysics Laboratory, Butantan Institute, Sao Paulo, SP, Brazil. J Cutan Pathol 2005: 32: 323–328 Copyright # Blackwell Munksgaard 2005 Blackwell Munksgaard. Printed in Denmark Journal of Cutaneous Pathology 323