Fig. 4.

Representative examples of SMARCA4-deficient sinonasal carcinoma. A SMARCA4-deficient sinonasal carcinoma show a predominance of large undifferentiated cells with variable lobular pattern mimicking SNUC and large cell neuroendocrine carcinoma. B cytological uniformity with variably prominent nuclei and brisk mitotic activity. C rarely, abrupt transition from large cell (right) to blue-stained ovoid cells mimicking small cell carcinoma (left) is seen; note foci of necrosis on right. D main image: calretinin as well as synaptophysin (not shown) are expressed at the periphery of the cell aggregates suggesting hybrid olfactory-like features. D subimage: complete loss of SMARCA4 is the defining feature of these tumors