A 40-year-old woman with a slow-growing mass in the nasal cavity undergoes excision; histology shows cribriform and tubular patterns of basaloid cells with hyaline material. Over the next two years she develops diplopia and numbness in the V2 distribution despite complete excision. The feature best explaining this course is:

• A Haematogenous spread to bone marrow
• B Radiation-induced neuropathy from prior therapy
• C Transformation to undifferentiated carcinoma
• D Perineural spread along branches of the trigeminal nerve ✓

Explanation

This is adenoid cylindromatous carcinoma (adenoid cystic carcinoma) of the sinonasal tract, which characteristically spreads along nerves, particularly the maxillary division of the trigeminal nerve entering via the foramen rotundum. Perineural extension explains delayed facial numbness, diplopia from cavernous sinus involvement, and local recurrence years after apparently complete excision. It also metastasises late to lung and bone, but the cranial neuropathies described here point specifically to perineural spread.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.