Cytologic distinction of metastatic cystic squamous cell carcinoma (SCC) from benign squamous cell lesions, especially the ones with superimposed inflammatory atypia, can be very challenging. The authors evaluated the usefulness of glucose transporter-1 (GLUT-1) immunostaining as an adjunct to fine-needle aspirations of squamous lesions of the head and neck.
Immunohistochemical staining for GLUT-1 was performed on paraffin-embedded cell blocks of 28 cases with the following cytologic diagnoses: 1) metastatic SCC (11 cases); 2) atypical squamous cells, SCC [corrected] cannot be excluded (6 cases); and 3) cytologic findings consistent with branchial cleft cyst (BCC) (11 cases).
All 11 cases with an unequivocal cytologic diagnosis of metastatic SCC were positive for GLUT-1. Tissue follow-up confirmed metastatic SCC in all 11 cases. The squamous cells in all 11 cases with cytologic findings consistent with BCC were negative for GLUT-1; tissue follow-up confirmed diagnoses of BCC in 8 cases. In the remaining 3 cases, excision was not performed, and, clinically, no recurrences were identified at 28, 20, and 16 months of follow-up. Of the 6 cases with cytologic diagnosis of atypical squamous cells, 3 were negative and 3 were positive for GLUT-1. Subsequent excisional biopsies in these cases revealed 4 cases of metastatic SCC (3 positive and 1 negative for GLUT-1), 1 case of BCC (negative for GLUT-1), and 1 case of thyroglossal duct cyst (negative for GLUT-1).
GLUT-1 immunostaining is a useful adjunct in differentiating benign and malignant squamous lesions in cell-block material. Although negative staining for GLUT-1 does not exclude malignancy, positive immunoreactivity for GLUT-1 may aid in accurate diagnosis of malignancy in cytomorphologically equivocal squamous lesions of the head and neck.