Adenoid Cystic Carcinoma with Striking Tubular Hypereosinophilia: A Subtype Associated with Non-parotid Location and Both Canonical and Novel EWSR1::MYB and FUS::MYB Fusions
Abstract
The classification of salivary gland tumors is ever evolving with next-generation sequencing (NGS) helping to refine this classification. Adenoid cystic carcinoma (AdCC) is one of the most common salivary malignancies, occurring at all salivary and seromucous gland sites.
Most AdCC are predominantly basaloid, with cribriform, tubular and solid growth. The luminal tubular elements are often less conspicuous.
AdCC has largely been characterized by canonical MYB::NFIB and MYBL1::NFIB fusions. Some AdCC, mostly in non-major salivary gland sites, have been noted to have unusual patterns, including squamous differentiation.
Recently, this led to the recognition of a subtype: "metatypical AdCC". Occasional cases have also shown more prominent luminal cells with hypereosinophilia or complex architecture, such as micropapillary or glomeruloid growth.
These have not been proven to carry MYB fusions.