Watanabe Hiromu

1 Introduction Pulmonary basaloid squamous cell carcinoma (BSCC) is a rare histologic subtype of squamous cell carcinoma (SCC) of the lung. First described by Brambilla et al. in 1992, it is now classified in the fifth edition of the WHO classification as a high-grade variant of SCC with poor prognosis [1]. Histologically, BSCC is defined by small basaloid cells with hyperchromatic nuclei and scant cytoplasm, forming solid nests with peripheral palisading and frequent mitotic figures.