Low-grade sinonasal adenocarcinomas: the association with and distinction from respiratory epithelial adenomatoid hamartomas and other glandular lesions.

Sinonasal adenocarcinomas (SNACs) are uncommon malignancies that show a variety of growth patterns. These lesions are classified as intestinal or nonintestinal, the latter subclassified as low grade or high grade. We have noted that some low-grade nonintestinal SNACs are associated with respiratory epithelial adenomatoid hamartomas (REAHs), also rare lesions that have recently been shown to be neoplastic. We reviewed 29 nonintestinal low-grade SNACs seen at our institution over a 20-year period, with particular attention to morphology and concomitant REAHs. Nine (31%) low-grade SNACs demonstrated a predominantly exophytic and papillary growth pattern, and 18 (72%) had a more tubular growth pattern. Two (7%) were categorized as "other." Six low-grade tubular SNACs were associated with REAHs. An immunohistochemical panel was performed on 2 of these cases; neoplastic cells were immunoreactive with antibodies to CK7 and S100 protein and nonreactive with antibodies to CK20, similar to other low-grade SNACs. No basal cells or myoepithelial differentiation was seen with immunohistochemical stains for p63 and 34betaE12. This association of low-grade tubular SNACs with REAHs suggests that REAHs may be related to some adenocarcinomas.