Atypical adenoid cystic carcinoma of the palate during pregnancy: a case report

Adenoid cystic carcinoma (ACC) of the palate is a malignant salivary gland neoplasm typically characterized by perineural invasion, recurrent MYB-NFIB fusion, and an indolent clinical course. We report an atypical case of palatal ACC arising during pregnancy that exhibited rapid progression, upregulated estrogen receptor (ER) expression, and atypical histopathology. ACC most frequently involves the parotid and palatal glands and is histologically stratified into cribriform, tubular, and solid subtypes, with solid pattern carrying the poorest prognosis. The tumor is characteristically indolent yet relentless, with a marked propensity for perineural invasion, which often manifesting as pain, facial paralysis, or lingual numbness and a preference for hematogenous over lymphatic spread, with lungs as the most common site of distant metastasis. Wide local excision remains the cornerstone of treatment. The patient first presented in early pregnancy with focal microvascular congestion and pain of the palatal mucosa. Within 24 weeks, the lesion progressed to full-thickness perforation of the palatal mucosa and underlying bone. After delivery by cesarean section at 37 weeks of gestation and hospital admission, imaging revealed bilateral cervical lymph node involvement and bilateral pulmonary metastases, a trajectory that diverges sharply from the slow-growing course typical of ACC. Immunohistochemistry demonstrated small cribriform architecture with patchy or absent expression of conventional myoepithelial markers. Fluorescence in situ hybridization (FISH) confirmed an MYB-NFIB fusion, the hallmark molecular alteration of ACC, anchoring the diagnosis despite the unusual phenotype. Notably, ER expression was upregulated in tumor tissue, suggesting that gestational hormonal shifts may have modulated tumor progression; however, the marked nuclear atypia, high proliferative index, and early nodal and pulmonary metastasis were more consistent with intrinsic high-grade transformation of ACC. After integrating clinical, biological, molecular, and genotypic findings and excluding morphological mimics, the final diagnosis was atypical ACC of the palate. This case underscores the need for heightened clinical vigilance toward focal palatal microvascular congestion during pregnancy, which may herald an aggressive oral malignancy in this hormonally distinct population. Early recognition, supplemented by molecular confirmation (MYB-NFIB FISH) when histology is equivocal, is essential for timely intervention and improved outcomes in atypical, pregnancy-associated ACC of the oral and maxillofacial region.