Differential diagnosis of solid carcinoma in situ

Significance of rat mammary tumors for human risk assessment

We have previously indicated that the ideal animal tumor model should mimic the human disease. This means that the investigator should be able to ascertain the influence of host factors on the initiation of tumorigenesis, mimic the susceptibility of tumor response based on age and reproductive history, and determine the response of the tumors induced to chemotherapy. The utilization of experimental models of mammary carcinogenesis in risk assessment requires that the influence of ovarian, pituitary, and placental hormones, among others, as well as overall reproductive events are taken into consideration, since they are important modifiers of the susceptibility of the organ to neoplastic development. Several species, such as rodents, dogs, cats, and monkeys, have been evaluated for these purposes; however, none of them fulfills all the criteria specified previously. Rodents, however, are the most widely used models; therefore, this work will concentrate on discussing the rat rodent model of mammary carcinogenesis.

Ductal carcinoma in situ of the breast: current concepts and future directions

CONTEXT

In situ carcinomas of the breast constitute 15% to 30% of all newly diagnosed breast cancer cases; 80% of these in situ lesions belong to the ductal carcinoma in situ (DCIS) category. Similar to invasive breast carcinomas, DCIS is not a single disease but rather many distinct diseases with different histopathologic and molecular characteristics, a propensity to progress to invasive disease, and differential response to treatment.

OBJECTIVE

To review the classic pathologic parameters of clinical significance and the differential diagnosis of the DCIS lesions, present our new understanding of the importance of biomarkers, and discuss innovative approaches for targeted therapy in DCIS.

DATA SOURCES

Extensive review of the relevant peer-reviewed literature.

CONCLUSIONS

In DCIS, improved understanding of the underlying biologic pathways of tumor progression is expected to lead to more accurate classification and innovative targeted treatment approaches for the management of these lesions.

Lobular in situ neoplasia and columnar cell lesions: diagnosis in breast core biopsies and implications for management

Histopathologists are encountering intra-lobular epithelial proliferations more frequently in core biopsies taken from lesions identified in mammographic breast screening programmes. In particular, columnar cell lesions are increasingly being seen in core biopsies taken for the histological assessment of mammographically detected microcalcifications. The morphological features of lobular neoplasia are relatively well known, but columnar cell lesions, particularly forms with atypical features, are less widely recognised. The biological and clinical significance of both of these intra-lobular processes is controversial, (1) as indicators of adjacent malignancy when encountered in core biopsy, (2) the relative risk conferred of development of subsequent malignancy, and (3) their precursor behaviour. For this reason, the optimal clinical management of these lesions, particularly when encountered on core biopsy, is unclear. This review provides an update on the histological diagnosis of lobular neoplasia and columnar cell lesions and outlines recent clinico-pathological and molecular findings with discussion on clinical management.

Non-operative breast pathology: lobular neoplasia

Lobular neoplasia is a relatively uncommon lesion, which is frequently diagnosed in biopsy specimens taken for other reasons. Although the histological features of this lesion are well known, its biological significance as a "risk indicator" or "breast cancer precursor" has been a matter of debate. This review provides an update on recent clinicopathological and molecular data on lobular neoplasia and how these have changed the way these lesions are perceived and, most importantly, managed. Furthermore, the current recommendations for the management of lobular neoplasia diagnosed on core needle biopsies proposed in the National Health Service Breast Cancer Screening guidelines are discussed.

Lobular Intraepithelial Neoplasia [Lobular Carcinoma In Situ] With Comedo-type Necrosis

The recent finding that lobular, and not ductal intraepithelial neoplasia (DIN) displays loss of E-cadherin expression has greatly facilitated the categorization of a large proportion of morphologically ambiguous intraepithelial neoplasias into ductal or lobular types. One reason for such morphologic ambiguity is the presence of comedo-type necrosis within an intraepithelial lesion that otherwise shows archetypal cytologic and architectural features of lobular intraepithelial neoplasia (LIN). The clinicopathologic features of 18 such cases are described in this report. These 18 cases of classic LIN were accumulated from the recent databases of 6 institutions. All cases, by definition, showed no expression of E-cadherin. The 18 patients, all women, were 41 to 85 years of age (mean 61.3). The lesions were initially identified in an excisional biopsy or mastectomy in 12 cases and in an incisional/core biopsy in the remaining 6 cases. An associated invasive carcinoma was present in 12 (67%) of 18 cases (7 classic lobular, 1 pleomorphic lobular, 1 ductal, 1 mixed lobular and ductal, 1 tubular, and 1 case with ductal and lobular carcinomas as separate foci). The average age of the 6 patients with pure LIN (ie, LIN without an invasive component (62.5 y) was not significantly different from the 12 patients in which there was an invasive component (60.7 y) (P = 0.78). The lesions had associated calcifications, typically within the necrotic foci, in 10 (55%) of 18 cases. Immunoreactivity for estrogen receptor, progesterone receptor (in >10% of lesional cells), and high-molecular weight keratin was present in 17/18 (94%), 15/18 (83%) and 17/18 (94%) of cases, respectively. Overexpression of HER2/neu, as assessed immunohistochemically, was absent in all 15 cases available for such evaluation. Foci of DIN, separate from the lobular lesions, were present in 6 (33%) of 18 cases. LIN with necrosis seems to occur at an older age than classic LIN, is commonly associated with invasive carcinoma and is significantly more frequently associated with lobular than ductal invasive carcinoma. When present without an invasive component, it may be mistaken for DIN 2 (grade 2 ductal carcinoma in situ). Although the necrosis suggests a ductal phenotype for these intraepithelial proliferations, architectural and cytologic features, high-molecular weight keratin[+], estrogen receptor[+], progesterone receptor[+], and human epidermal growth factor receptor 2 /neu[-] immunoprofile, frequent association with invasive lobular carcinoma, and lack of immunoreactivity for E-cadherin, strongly suggests that these lesions are within the morphologic spectrum of lobular neoplasia. Long-term follow-up studies are required to define the true natural history of these lesions. However, because classic LIN with necrosis is apparently rare in its pure form, reexcision is recommended when this lesion is detected in isolation in a core biopsy.

Pleomorphic lobular carcinoma of the breast: role of comprehensive molecular pathology in characterization of an entity

Immunohistochemical analysis of E-cadherin has changed the way lobular neoplasia is perceived. It has helped to classify difficult cases of carcinoma in situ with indeterminate features and led to the identification of new variants of lobular carcinoma. Pleomorphic lobular carcinoma (PLC) and pleomorphic lobular carcinoma in situ (PLCIS), recently described variants of invasive and in situ classic lobular carcinoma, are reported to be associated with more aggressive clinical behaviour. Although PLC/PLCIS show morphological features of classic lobular neoplasia and lack E-cadherin expression, it is still unclear whether these lesions evolve through the same genetic pathway as lobular carcinomas or are high-grade ductal neoplasms that have lost E-cadherin. Here we have analysed a case of extensive PLCIS and invasive PLC associated with areas of E-cadherin-negative carcinoma in situ with indeterminate features, using immunohistochemistry, chromogenic in situ hybridization, high-resolution comparative genomic hybridization (CGH) and array-based CGH. We observed that all lesions lacked E-cadherin and beta-catenin and showed gain of 1q and loss of 16q, features that are typical of lobular carcinomas but are not seen in high-grade ductal lesions. In addition, amplifications of c-myc and HER2 were detected in the pleomorphic components, which may account for the high-grade features in this case and the reported aggressive clinical behaviour of these lesions. Taken together, these data suggest that at least some PLCs may evolve from the same precursor or through the same genetic pathway as classic lobular carcinomas.