Definition
• A histological variant of SCC with prominent peripheral palisading of nuclei
Clinical features
Epidemiology
• Same as other SCCs
Presentation
• Same as other SCCs
Prognosis and treatment
• Surgical resection and radiation therapy
• Unfavorable prognosis
Pathology
Histology
• Poorly differentiated tumor cells with prominent peripheral palisading of nuclei
• Squamous differentiation may be present focally with keratinization or intercellular bridges
Immunopathology/special stains
• Very useful for diagnosis, especially when no squamous differentiation is present
• Same as other SCCs: positive for p63 and CK5/6
Main differential diagnoses
• Basaloid variant of large-cell carcinoma: no squamous differentiation; negative for p63 and CK5/6
• Adenoid cystic carcinoma: younger patients with a better prognosis; two cell types, usually with tubular formation or a cribriform pattern
Fig 1 Basaloid variant of squamous cell carcinoma. CAM5.2 stains the tumor cell cytoplasm focally (A) in contrast to strong staining with CK5/6 (B).
Fig 2 Basaloid variant of squamous cell carcinoma. Immunohistochemical stain for p63 is strongly positive in tumor nuclei.
Fig 3 Basaloid variant of squamous cell carcinoma. Needle biopsy of basaloid SCC at low (A), medium (B), and high (C) powers with peripheral nuclear palisading, few mitoses, and no nucleoli.