TTF1 and cervical small cell carcinoma: Additionally, P53 in metastatic small cell lung carcinoma is often mutated, while P53 in cervical small cell carcinoma is typically wild-type.[11] Furthermore, P16 is diffusely expressed in most cases of cervical small cell carcinoma, suggesting HPV association, which is not a characteristic feature of small cell lung carcinoma.[12] In 4 cases, cases 1 and 2 were TTF-1 positive, but there were no space-occupying lesions in the lungs, and all 4 cases had wild-type P53 and diffuse positivity for P16.