Page 544 - Concise Pathology for Exam Preparation ( PDFDrive )

19 The Breast 529

Pathology of Carcinoma Breast
1. Noninvasive lesions
(a) DCIS or intraductal carcinoma
(i) Most frequently presents as mammographic calcifications; less frequently, as a
vaguely palpable mass or nipple discharge. The incidence of DCIS has
increased from 5% to 15–30% of all breast carcinomas over the past few years,
attributable perhaps to the increasing use of mammographic screening.
(ii) It may be an incidental finding on biopsy.
(iii) Consists of a malignant population of cells limited to the ducts by basement
membrane.
(iv) Myoepithelial cells are preserved though may be decreased in number.
(v) Clonal proliferation of cells usually involving a single ductal system.
(vi) Has two main architectural subtypes:
- Comedocarcinoma
- Characterized by solid sheets of pleomorphic cells with central
necrosis.
- Necrotic cell membranes frequently calcify and are seen on mammogra-
phy as speckled microcalcifications, which may be grouped together or
arranged in parallel lines.
- Periductal concentric fibrosis and inflammation is common.
- Extensive lesions may be palpable as vague nodularity.
- Noncomedo DCIS
- Does not show cellular pleomorphism or central necrosis.
- May show different architectural patterns.
- Consist of a monomorphic population of cells completely filling up the
duct lumina (solid type), cells may grow into the spaces lining fibrovas-
cular cores (papillary DCIS), or project into the spaces without definite
fibrovascular cores forming complex intraductal patterns (micropapillary
DCIS). Cribriform DCIS has a cribriform pattern with round spaces
between cell aggregates.
(b) LCIS
(i) Usually, an incidental finding in breast biopsies performed for some other
reason.
(ii) Not associated with a clinically apparent mass or a mammographic abnormal-
ity (calcification or stromal reaction); so not readily diagnosed.
(iii) Bilateral in up to 40% of the patients when both breasts are biopsied.
(iv) LCIS is an intraepithelial proliferation of the TDLU. The cells of atypical lobular
hyperplasia, LCIS and invasive lobular carcinoma are identical, ie, loosely cohe-
sive, small with oval-to-round nuclei and small nucleoli. LCIS is diagnosed
when the entire lobular unit is replaced by tumour cells.
(v) Signet ring cells containing mucin are frequently seen.
2. Invasive carcinomas
• The terminology for the most common type of breast cancer has changed from
invasive ductal carcinoma, not otherwise specified (NOS; 2003) to invasive
carcinoma of no special type (NST; 2012). This group of breast cancers
comprises all tumours without the specific differentiating features that character-
ize the other specific categories of breast cancers. The name ‘ductal’ has been
omitted as it indicates derivation of the tumours from only the ductal system.
The use of ‘carcinoma of no special type’ is the preferred term. The diagnosis is
made by exclusion of recognized specific types of breast cancers. Other types of
breast cancer with specific features are regarded as invasive ductal carcinomas,
albeit of special type.
• The most common specific subtypes include invasive lobular, tubular, cribriform,
metaplastic, apocrine, mucinous, papillary and micropapillary carcinoma, as well as
carcinoma with medullary, neuroendocrine and salivary gland/skin adnexal type
features. These specific tumour types are defined by their morphology, but these are
also linked to particular clinical, epidemiological and molecular features.

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