Small cell variant of squamous cell carcinoma mimicking small cell lung carcinoma Case 292
This is a very instructive case of the small cell variant of squamous cell carcinoma (SCC) mimicking small cell lung carcinoma (SCLC) based not only on morphologic features but also on the results of immunostains. CD56 and CK5/6, the immunostains that were initially obtained were both positive. TTF 1, chromogranin A and synaptophysin were negative. A small percentage of squamous cell carcinomas may express CD56 and a small percentage of high grade neuroendocrine carcinomas may express CK5/6. p63 and p40 stains were subsequently obtained and both were positive confirming the diagnosis of SCC. AE1/AE3 was also positive but did not exhibit the dot like staining of the nuclear membranes that is often seen in SCLC. Careful examination of cell morphology at higher magnifications shows some cells with eosinophilic cytoplasm. Nuclear detail is lacking in these images.
Case contributed by Dr. Jian-Hua Qiao.