Comparative study of CD34, α-SMA and h-caldesmon expression in the stroma of gynaecomastia and male breast carcinoma

Aims : To address the fibroblastic/myofibroblastic nature of stroma in gynaecomastia and in male breast carcinoma, the expression of CD34, α‐smooth muscle actin (SMA) and h‐caldesmon in the stromal cells was investigated by immunohistochemistry. Methods and results : Representative archival paraffin blocks were collected from male patients with gynaecomastia (32 cases) and mammary carcinoma (24 cases) between 1984 and 2004 and CD34, α‐SMA and h‐caldesmon were assessed immunohistochemically using a streptavidin–biotin method. Thirty cases of gynaecomastia showed a CD34+, α‐SMA– and h‐caldesmon– immunophenotype with different CD34 staining intensity in the various histological subtypes. Positivity for α‐SMA and negativity for CD34 and h‐caldesmon was found in a case of florid gynaecomastia relating to reactive fibrosis due to previous surgical intervention. Acquisition of α‐SMA expression by stromal fibroblasts but absence of CD34 staining was identified in 22 cases of male breast carcinoma. Conclusions : The immunophenotype of periductal connective tissue stroma in gynaecomastia appears to parallel the phenotype of normal breast stroma. In male breast carcinoma the stromal cell immunophenotype is similar to that of its female counterpart showing myofibroblastic differentiation. However α‐SMA+ and CD34– are not specific to malignancy because such findings are also encountered in reactive fibrosis.