The result of bone puncture biopsy supported small-cell carcinoma, which was likely to originate from the lung based on the immunohistochemistry and morphology analysis, and immunohistochemistry results were a positive staining for Ki-67 (approximately 80%), CKpan, TTF-1, CgA, Syn, Insulinoma-associated protein 1 (INSM1), Retinoblastoma gene product (RBGP), and P53 (approximately 80%) and a strongly positive staining for SSTR2; simultaneously, it indicated a negative staining for NapsinA, P504S, PSA, Vimentin, CK7, P40, and NKX3.1 (Figure 4C). Here, KRT7 is linked to small cell carcinoma.