Update from the 4th Edition of the World Health Organization Classification of Head and Neck Tumours: Tumors of the Nasal Cavity, Paranasal Sinuses and Skull Base

Abstract

The sinonasal tract remains an epicenter of a diverse array of neoplasia. This paper discusses changes to the WHO classification system of tumors involving this area. In particular, seromucinous hamartoma, NUT carcinoma, biphenotypic sinonasal sarcoma, HPV-related carcinoma with adenoid cystic features, SMARCB1-deficient carcinoma, and renal cell-like adenocarcinoma are discussed.

Keywords: Adenoid cystic; Biphenotypical sinonasal sarcoma; Human papillomavirus; INI1; NUT carcinoma; Nasal; Seromucinous hamartoma; Sinonasal; Sinus; WHO.

Fig. 1

Squamous cell carcinoma. a Typical keratinizing squamous cell carcinoma of the sinonasal tract with abundant keratin formation. b Non-keratinizing squamous cell carcinoma with ribbons of immature squamous cells

Fig. 2

Adenocarcinoma. a Intestinal-type adenocarcinoma with mucus production. b Low-grade sinonasal adenocarcinoma with typical papillary architectures. c, d Two examples of high-grade sinonasal adenocarcinoma showing some of the heterogeneity that can be seen

Fig. 3

Seromucinous hamartoma. a Low-power image showing abundant small seromucinous glands with occasional larger, cystically dilated glands. b High-power showing bland seromucinous glands with back-to-back architecture. c S100 immunostain highlights the bland seromucinous glands. d p63 immunostain shows an absence of basal and myoepithelial cells

Fig. 4

NUT carcinoma. a NUT carcinoma grows as nests of tumor cells in the sinonasal submucosa, without a surface epithelial component. a neutrophilic infiltrate is seen. b Most cases of NUT carcinoma demonstrate focal squamous differentiation (arrow) in an abrupt pattern. c NUT carcinoma is usually positive for p40. (D) The diagnosis of NUT carcinoma can be confirmed with diffuse immunoreactivity for NUT protein, typically with a distinctly speckled pattern

Fig. 5

Biphenotypic sinonasal sarcoma. a Biphenotypic sinonasal sarcoma often demonstrates entrapment of downward extensions of surface epithelium, a pattern that can mimic inverted papilloma. b The tumor typically consists of fascicles of uniform spindled cells with elongated, hypo chromatic nuclei growing in a herringbone pattern. c Biphenotypical sinonasal sarcoma demonstrates varying degrees of immunostaining for S100. d Most cases are positive for smooth muscle markers like actin

Fig. 6

HPV-related adenoid cystic-like carcinoma. a Sinonasal HPV-related carcinoma with adenoid cystic-like features grows as nests and cribriform structures. Squamous dysplasia is seen in the overlying surface epithelium. b An immunostain for CK7 highlights the ductal structures. c An immunostain for p40 highlights only the basaloid myoepithelial cells, sparing the ducts. d The carcinoma is strongly positive for high-risk HPV by RNA in situ hybridization

Fig. 7

SMARCB1 Deficient carcinoma. a SMARCB1-deficient sinonasal carcinomas typically grow as nests and cords of undifferentiated cells. b Some cases exhibit prominent plasmacytoid or rhabdoid morphology. c Other examples are more basaloid in appearance, with only focal plasmacytoid/rhabdoid features (center). d By definition, these tumors demonstrate a complete absence of SMARCB1 immunoreactivity, with the background stromal and inflammatory cells showing intact staining

Fig. 8

Renal cell-like adenocarcinoma. a Renal cell carcinoma-like sinonasal adenocarcinoma consists of nests and follicles of polygonal cells with small round nuclei and optically clear cytoplasm. b Unlike metastatic renal cell carcinoma, renal cell carcinoma-like sinonasal adenocarcinoma is negative for PAX8