p53 immunolocalization in cell block preparations of squamous lesions of the neck - An adjunct to fine-needle aspiration diagnosis of malignancy

Objective.-Mutations of the p53 tumor suppressor gene, with consequent nucl ear p53 protein accumulation, are among the most common genetic abnormaliti es in human cancers. The purpose of this study was to determine the utility of p53 immunostaining as an adjunct to the diagnosis of malignancy in fine -needle aspirations of squamous lesions of the neck. Materials and Methods.-Using a monoclonal antibody to the p53 protein and a standard avidin-biotin complex technique, immunostaining was performed on paraffin-embedded cell blocks of 20 cases with the following cytologic diag noses: (1) metastatic squamous cell carcinoma (SCC) (7 cases); (2) atypical squamous cells, SCC cannot be excluded (7 cases); and (3) cytologic findin gs consistent with branchial cleft cyst (6 cases). Tissue or clinical follo w-up was available in all cases. Results.-Five (71%) of 7 cases with an unequivocal cytologic diagnosis of m etastatic SCC were positive for p53 protein. Tissue follow-up confirmed met astatic SCC in all of these 7 cases. Of the 7 cases with cytologic diagnosi s of atypical squamous cells, 2 were negative and 5 (71%) were positive for p53 protein. Subsequent excisional biopsies in these cases revealed metast atic SCC (6 cases) and branchial cleft cyst (1 case). The squamous cells in all 5 cases with cytologic findings consistent with branchial cleft cyst w ere negative for p53 protein; tissue follow-up confirmed the diagnoses of b ranchial cleft cyst in 4 cases. In the remaining 2 cases excision was not p erformed, as the cystic lesion was completely decompressed and, clinically, no recurrences were identified at 14 and 8 months of follow-up. Conclusions.-Our findings suggest that p53 immunostaining is helpful in dif ferentiating benign and malignant squamous lesions. While negative staining for p53 does not exclude malignancy, positive immunostaining may aid in ac curate fine-needle aspiration diagnosis of malignancy in cytomorphologicall y equivocal squamous lesions of the neck.