The distinction between lobular and ductal lesions of the breast is important in several circumstances. Diagnostic reproducibility of lobular versus ductal lesions, based on histology alone, is less than optimal. The proper distinction between atypical lobular
hyperplasia,
lobular carcinoma in situ and low-grade
ductal carcinoma in situ is critical for patient management. Patients who have a core biopsy of invasive
lobular carcinoma often have preoperative magnetic resonance imaging to prepare the surgeon for proper margin attainment.
E-cadherin, a negative membrane marker for lobular
neoplasia, is useful in the distinction of lobular versus ductal
neoplasia, but as a negative marker, can be difficult to interpret in particularly challenging cases. In this study, we surveyed primary and metastatic ductal lesions (62) and lobular lesions (64) of the breast to determine if P120
catenin is useful in the diagnostic distinction between lobular and ductal
neoplasia. Primary breast ductal and lobular preneoplastic and neoplastic lesions were immunostained with
E-cadherin and
P120ctn and independently classified as ductal or lobular lesions. In addition, a wide array of
carcinomas of different types were surveyed with
P120ctn in tissue microarrays to ascertain whether the cytoplasmic
P120ctn immunostaining pattern observed in lobular
neoplasia was unique. Accurate categorization of ductal versus lobular
neoplasia in the breast with
P120ctn immunostaining was effective in all cases. Separation of low-grade
ductal carcinoma in situ from lobular
neoplasia was efficient. Diagnostically,
P120ctn was particularly useful in identifying early lesions of lobular
neoplasia. Of the other
tumors that may morphologically mimic
lobular carcinoma, only the diffusely infiltrating variants of rectal and gastric
carcinomas showed diffuse cytoplasmic
P120ctn immunostaining. Caution should be exercised when examining
tumors in metastatic sites with
P120ctn, with the incorporation of an appropriate panel of immunostains.