Heterogeneous expression of nm23 gene product in noninvasive breast carcinoma

The two major types of noninvasive breast carcinoma, ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS), are quite different in their histopathologic appearance and clinical implications. LCIS is only a marker of an increased risk of later development of invasive carcinoma, whereas most DCIS lesions are at least nonobligate precursors of invasive carcinoma. DCIS is a heterogeneous group of lesions composed of several distinct subtypes, with only the comedo subtype having immediate malignant potential. The authors' purpose was to analyze noninvasive carcinomas for the presence of a gene product (nm23) indicative of a favorable prognosis in invasive carcinomas to determine differences (1) among the different types of CIS and (2) in CIS with and without an accompanying invasive component.

Immunohistochemical methods were used to detect nm23 gene product in archival material from two groups of patients: Group 1 consisted of 54 cases of purely noninvasive carcinoma, and Group 2 consisted of 55 examples of noninvasive carcinoma associated with an invasive component.

Among the cases of CIS with no invasion, LCIS and comedo DCIS expressed more nm23 than noncomedo DCIS (P < or = 0.03). There were no differences among these CIS subtypes in the group with invasion. Comparing subtypes of CIS in the groups with or without invasion, only comedo DCIS was significantly different, with greater expression in the CIS group with no invasion compared with comedo DCIS associated with an invasive component (P = 0.04).

These results support the special nature of LCIS and the heterogeneous nature of DCIS. The in situ component attending an invasive component may be different from anatomically similar lesion without associated invasion. The absence of nm23 in comedo DCIS may be indicative of invasive capacity.