Intercalated duct lesions of salivary gland: a morphologic spectrum from hyperplasia to adenoma

Intercalated duct lesions (IDLs) are rare, poorly understood and not well-studied lesions that have been associated with a small number of epithelial-myoepithelial carcinomas (EMC) and basal cell adenomas. To examine the nature of IDLs and their association with salivary gland tumors, we reviewed 34 lesions in 32 patients. The IDLs were stained with CK7, estrogen receptors (ER), progesterone receptors, lysozyme, S100, calponin, and CK14. The patients ranged in age from 19 to 80 years (mean 53.8) with a 1.7:1 female predominance. The majorities of IDLs were parotid lesions (82%), were small and nodular (average size 3.1 mm) and showed 3 architectural patterns: hyperplasia (20), adenoma (9), and hybrid forms (5). In 59% of cases, IDLs were seen in conjunction with another salivary gland tumor, most commonly basal cell adenoma (8 cases), followed by EMC (3 cases). One case showed a combination of intercalated duct hyperplasia and basal cell adenoma. The IDLs stained diffusely with CK7 (100%) and S100 (73%) and focally for ER (91%) and lysozyme (100%). Calponin and CK14 highlighted a thin myoepithelial cell layer around all ducts (100%). Normal intercalated ducts were also consistently positive for CK7 and lysozyme, and focally for ER, but were S100 negative. In summary, IDLs have a variety of patterns ranging from hyperplasia to adenoma with hybrid lesions and share morphologic and immunophenotypic features with normal intercalated ducts. There is an association with basal cell adenomas and EMC, which lends credence to their role as a putative precursor lesion.