Perineural invasion has been reported in DTE, (50) but perineural invasion in any infiltrative basaloid neoplasm should be cause for extreme caution.
Practical Approach to the MAC Differential Diagnosis: If the biopsy specimen is small and the diagnosis uncertain, the authors use the top line diagnosis "infiltrative basaloid neoplasm (see comment)," state which entity is favored, list the other entities in the differential diagnosis, and recommend conservative complete excision to visualize the whole lesion.
Going beyond "basaloid neoplasm
": fine needle aspiration cytology of epithelial-myoepithelial carcinoma of the parotid gland.
One of the challenging issues within the basaloid neoplasm category is the diagnosis of AdCC on cytology aspirate.
Other markers that could be useful in the setting of a basaloid neoplasm in which AdCC is in the differential diagnosis have been investigated on resection specimens, rather than cytologic material.
This typically results in a descriptive FNA biopsy diagnosis and is reported as a "basaloid neoplasm" with a comment detailing the differential diagnostic possibilities and limitations of definitive classification because of the morphologic appearance.
Detecting a MYB translocation in a FNA biopsy specimen with the morphologic diagnosis of "basaloid neoplasm" could provide a more precise preexcision diagnosis of AdCC.
"Breast pathologists" should practice with an ever-present awareness that the target of their usual study is intimately wrapped in another potentially tumorigenic organ, the skin, and that the skin itself can give rise to both benign and malignant basaloid neoplasms
However, if the stromal component is scanty or missing, and smears are highly cellular, the distinction from basaloid neoplasms
and myoepithelial adenoma can be difficult or even impossible.
The solid variant of ACC is therefore much more difficult to diagnose on FNA than the classic type, and it is usually suggested as part of a differential diagnosis, typically in the setting of basaloid neoplasms
Another limitation of both the study of Hudson and Collins, (1) as well as our study, (2) is that other less common basaloid neoplasms
that enter into the differential diagnosis of AdCC and PA were not evaluated.
This feature, along with accompanying areas of cribriform or tubular growth, can aid in differentiation from other basaloid neoplasms