Difficulty of the differential diagnosis of basal cell adenoma and basal cell adenocarcinoma of parotid gland by magnetic resonance imaging: case reports and literature review

Objectives The aim of this study was to assess the efficacy of magnetic resonance imaging (MRI) for the differential diagnosis of basal cell adenocarcinoma (BCAC) and basal cell adenoma (BCA) in the salivary gland. Methods Magnetic resonance imaging findings and pathological correlations were studied retrospectively in three cases of pathologically verified BCA and one case of BCAC. The MRI findings from previously reported cases (16 cases of BCA, 1 case of BCAC) were reviewed. Results All three BCAs showed well-defined margins, a round or ovoid shape, homogeneous hypointense signal on T1-weighted imaging (T1WI), and moderate contrast enhancement on contrast-enhanced T1WI. T2-weighted imaging showed heterogeneous hyperintense signals in two cases and a hypointense signal in one. The BCAC displayed MRI findings similar to those of the BCAs, with histopathologically verified partial invasion into the surrounding tissue remaining undetected. Time-signal intensity curves on dynamic MRI displayed rapid enhancement followed by a low washout pattern in all BCA cases, and a gradual enhancement pattern in the BCAC case. Both of these patterns are nonspecific and are commonly seen in other salivary tumors. Conclusions Both the BCAs and the BCAC showed nonspecific findings on MRI, making it difficult to distinguish between these entities, even with dynamic MRI.