Disappearance of primitive basaloid cells after external irradiation in adenoid cystic carcinoma of the lacrimal gland.

OBJECTIVE: To study the histopathological findings of basaloid adenoid cystic carcinoma after high dose orbital irradiation. MATERIAL AND METHOD: The histopathology study was done in a 38-year-old Thai female patient who had basaloid adenoid cystic carcinoma of the right lacrimal gland confirmed by incisional biopsy. After a 60-Gy external irradiation, the mass decreased in size and finally could not be palpated, but subsequent orbital imaging still showed infiltrative soft tissue mass at the right lacrimal gland with bony defects at posterosuperior and lateral walls without extraorbital extension. Orbital exenteration and lateral orbitectomy was performed. The specimen was submitted for histopathological examination. RESULTS: Microscopic examination revealed periglandular infiltration with chronic inflammation of the palpebral lobe of lacrimal gland. The orbital lobe was extensively replaced with fibrous tissue. There was only a small area of cribiform pattern of the adenoid cystic carcinoma left; no basaloid pattern was seen in the tissue. CONCLUSION: The primitive cells (basaloid pattern) disappear after orbital irradiation for adenoid cystic carcinoma of the lacrimal gland. Replacement with fibrous tissue is seen.