Abstract

We describe three cases of lung squamous cell carcinoma (SCC) metastatic to skin with diffuse BerEp4 positivity. The first patient, a 23-year-old female with lung SCC metastatic to bone presented with a scalp nodule which on biopsy showed highly atypical BerEp4 positive cells growing in sheets and infiltrative strands without epidermal connection. The second patient, a 74-year-old male with lung SCC metastatic to brain presented with a chest nodule which showed a BerEp4 positive atypical dermal squamous nodule without epidermal connection. The third patient, a 74-year-old male with no history of malignancy presented with multiple cutaneous nodules on the head and trunk, which on biopsies showed multiple BerEp4 positive atypical dermal squamous nodules without epidermal connection, prompting workup for visceral malignancy with eventual diagnosis of lung SCC. BerEp4, an antibody to epithelial cell adhesion molecule (EpCAM), is commonly used by dermatopathologists to distinguish basal cell carcinoma (BerEp4 positive) from primary cutaneous SCC (cSCC, BerEp4 negative) with high sensitivity and specificity, as cSCC is reliably negative for BerEp4. In one review, 116/117 of cSCC were negative and 1/117 was weakly positive for BerEp4. However, BerEp4 may be positive in SCC from lung and other visceral primary sites. Our case series suggests that when encountering atypical squamous tumors without epidermal connection in skin biopsies of patients with or without history of visceral malignancy, dermatopathologists may consider BerEp4 as a potential screening stain. Diffusely positive BerEp4 squamous cell carcinoma in skin should raise suspicion of cutaneous metastasis, such as from a lung primary.