Abstract
Uroplakin II antibody is exclusively specific for urothelial carcinoma. Nonurothelial carcinoma has not been reported to be immunoreactive for uroplakin II. In the present study, we hypothesized that breast carcinoma showing apocrine differentiation, such as invasive pleomorphic lobular carcinoma (IPLC) and apocrine carcinoma (AC), stains positive for uroplakin II. We identified 6 cases of IPLC between 2000 and 2014 by searching a computerized pathological database. We randomly selected 10 cases of each classic invasive lobular carcinoma (cILC) and AC and five cases of apocrine metaplasia (AM) that coexisted in a surgically resected breast carcinoma specimen. Immunohistochemistry was performed for uroplakin II, GATA3, CK7, CK20, and other representative markers positive for urothelial carcinoma. All cases of IPLC, AC, and AM, except those of cILC, showed immunoreactivity for uroplakin II. Poorly differentiated urothelial carcinoma sometimes shows similar morphology to IPLC with the following immunophenotype: CK7+, CK20−, GATA3+, and uroplakin II+. In the present study, this immunophenotype was observed in all the cases of IPLC and AC. Therefore, when studying metastatic, poorly differentiated carcinoma showing the aforementioned immunophenotype, we should consider the possibility of it being IPLC in addition to metastatic urothelial carcinoma.
Highlights
Developed uroplakin II antibody was found to be exclusively specific to the urothelium and urothelial carcinomas when evaluated in various normal and neoplastic tissues [1]
In addition to GATA3, uroplakin II is positive for metastatic carcinoma, it should be considered as metastatic urothelial carcinoma, as has been suggested by previous studies; to the best of our knowledge, no breast carcinoma has ever been reported to be positive for uroplakin II in the English language literature [1, 3, 4]
All the cases of apocrine metaplasia (AM) expressed uroplakin II with score 3+; half (3 of 6 and 5 of 10, resp.) of invasive pleomorphic lobular carcinoma (IPLC) and apocrine carcinoma (AC) showed uroplakin II expression of score 3+ with the rest of the cases exhibiting its expression of score 1+ or 2+; and classic invasive lobular carcinoma (cILC) was immunonegative for uroplakin II in all cases examined
Summary
Developed uroplakin II antibody (clone: BC21) was found to be exclusively specific to the urothelium and urothelial carcinomas when evaluated in various normal and neoplastic tissues [1]. It stained urothelium among 37 US Food and Drug Administration normal tissue types, including 3 breast tissue samples [1]. 20 tumor types were immunostained with it and urothelial carcinoma was exclusively positive for it, except for one of eighty-eight prostatic adenocarcinomas. In addition to GATA3, uroplakin II is positive for metastatic carcinoma, it should be considered as metastatic urothelial carcinoma, as has been suggested by previous studies; to the best of our knowledge, no breast carcinoma has ever been reported to be positive for uroplakin II in the English language literature [1, 3, 4]
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