The Myoepithelial Cells of Salivary Intercalated Duct-type Intraductal Carcinoma Are Neoplastic: A Study Using Combined Whole-slide Imaging, Immunofluorescence, and: RET: Fluorescence In Situ Hybridization

Intraductal carcinoma (IDC) is a salivary gland tumor currently believed to be analogous to breast ductal carcinoma in situ, consisting of a complex neoplastic epithelial proliferation surrounded by a continuous layer of myoepithelial cells presumed to be native and non-neoplastic. Recent molecular insights have shown that there are at least 3 different types of IDC: (1) intercalated duct-like, with frequent NCOA4-RET fusions; (2) apocrine, with multiple mutations similar to salivary duct carcinoma; and (3) mixed intercalated duct-like and apocrine with frequent RET fusions, especially TRIM27-RET. Recent observations (eg, IDC occurring in lymph nodes) have challenged the notion that the myoepithelial cells of IDC are non-neoplastic. Five IDCs with known RET fusions by RNA sequencing were retrieved from the authors’ archives, including 4 intercalated duct-like IDCs with NCOA4-RET, and 1 mixed intercalated duct-like/apocrine IDC with TRIM27-RET. A panel of immunohistochemistry antibodies (S100 protein, p63 or p40, mammaglobin, smooth muscle actin, calponin, androgen receptor) was tested. To precisely localize RET split-positive cells, each case was subjected to sequential retrieval of whole-slide imaging data of hematoxylin and eosin (HE) staining, immunofluorescence staining for calponin, and fluorescence in situ hybridization (FISH) for RET. Because NCOA4-RET is an inversion difficult to visualize on conventional RET FISH, a novel 3-color FISH technique was utilized to demo...
Source: The American Journal of Surgical Pathology - Category: Pathology Tags: Original Articles Source Type: research