Molecular classification of metaplastic carcinoma using surrogate immunohistochemical staining

The purpose of this study is to investigate molecular subtyping and its implications on metaplastic carcinoma according to surrogate immunohistochemical (IHC) staining.

Following tissue microarray analysis of 34 cases of metaplastic carcinoma, IHC staining for cytokeratin (CK) 5/6, epidermal growth factor receptor (EGFR), claudin-3, claudin-4, claudin-7, E-cadherin, STAT-1, androgen receptor and GGT was performed and classified into basal-like, molecular apocrine, claudin-low, immune-related, mixed and null types.

Among the 34 cases of metaplastic carcinoma, 13 were of the basal-like type (35.2%), 9 of the mixed type (26.5%), 8 of the null type (23.5%), 3 of the claudin-low type (8.8%), and 1 was of the molecular apocrine type (2.9%). Depending on the cell type, there were differences between molecular subtypes, with the matrix-producing type occupying the largest proportion in the basal-like, null and mixed types. The spindle cell type represented the largest proportion in the claudin-low and molecular apocrine types, and the squamous cell type characterized the largest proportion in the basal-like type.

Following molecular subtyping of metaplastic carcinomas using surrogate IHC markers, the largest number of cases was of the basal-like type, followed by the mixed, null, claudin-low and molecular apocrine types. There were differences between molecular subtypes according to the cell type.