WT1 immunoreactivity in breast carcinoma: selective expression in pure and mixed mucinous subtypes

Abstract

Current literature suggests that strong WT1 expression in a carcinoma of unknown origin virtually excludes a breast primary. Our previous pilot study on WT1 expression in breast carcinomas has shown WT1 expression in approximately 10% of carcinomas that show mixed micropapillary and mucinous morphology (Mod Pathol 2007;20(Suppl 2):38A). To definitively assess as to what subtype of breast carcinoma might express WT1 protein, we examined 153 cases of invasive breast carcinomas. These consisted of 63 consecutive carcinomas (contained 1 mucinous tumor), 20 cases with micropapillary morphology (12 pure and 8 mixed), 6 micropapillary 'mimics' (ductal no special type carcinomas with retraction artifacts), 33 pure mucinous carcinomas and 31 mixed mucinous carcinomas (mucinous mixed with other morphologic types). Overall, WT1 expression was identified in 33 carcinomas, that is, 22 of 34 (65%) pure mucinous carcinomas and in 11 of 33 (33%) mixed mucinous carcinomas. The non-mucinous component in these 11 mixed mucinous carcinomas was either a ductal no special type carcinoma (8 cases) or a micropapillary component (3 cases). WT1 expression level was similar in both the mucinous and the non-mucinous components. The degree of WT1 expression was generally weak to moderate (490% cases) and rarely strong (o10% cases). None of the breast carcinoma subtype unassociated with mucinous component showed WT1 expression.

Application of immunohistochemistry in the diagnosis of epithelioid mesothelioma: a review and update

“…These findings indicate that WT1 immunostaining can be useful in assisting in distinguishing epithelioid mesotheliomas from renal cell carcinomas. A great variation in WT1 expression has been reported in breast carcinomas, ranging from 0% in some early investigations [57,64] up to nearly 50% in more recent studies [23,65,66]. These findings indicate that WT1 immunostaining does not have the value in distinguishing breast carcinomas from mesotheliomas as was initially thought [3].…”

Mucinous Carcinoma with Neuroendocrine Differentiation of Salivary Gland Origin

“…[12,13] EMPSGC is uniformly WT-1 positive [14], while selective WT-1 expression has also been reported in pure and mixed mucinous subtypes of breast carcinomas. [15] However, WT-1 expression was negative in this specimen, arguing against an EMPSGC diagnosis. The described case is unusual in that it exhibits morphologic and immunohistochemical features similar to primary mammary mucinous adenocarcinomas, with neuroendocrine differentiation [16] in its receptor profile and GATA-3 positivity.…”

Practical Applications in Immunohistochemistry: Carcinomas of Unknown Primary Site

“…127 In the breast, WT1 is expressed in around 6% of the cases, usually at low levels in pure mucinous (65%) and mixed mucinous (33%) subtypes. 123,128 Estrogen Receptor.-Many healthy tissues and tumors, including a subset of carcinomas arising within the female genital tract, exhibit nuclear expression for ER. In endometrial carcinomas of endometrioid type (type 1), ER antibodies are reactive, whereas in uterine serous and clear cell carcinomas (type 2), they usually are not.…”