Ackerman Normal Anatomy

Normal Anatomy 

The breast or mammary gland is covered by skin and subcutaneous  tissue and rests on the pectoralis muscle, from which it is separated  by a fascial layer. 

The morphofunctional unit of the breast is a  

complex branching structure that is topographically 

arranged into  lobes and which is made up of two major components: 

1. terminal  duct–lobular unit (TDLU) and the 

2. large duct system.

The TDLU is formed by the lobule, 

1. made up of acini, and the 

2. terminal ductule and represents the 

3. secretory portion of the gland. 

• The TDLU is recognized by its distinctly lobular architecture, 

• the  presence of a mantle (intralobular stroma) of specialized, 

• myxoid-appearing hormone responsive connective tissue, and the 

• absence of elastic fibers.

ETD, Extralobular terminal duct; ITD, intralobular  terminal duct

large duct system.

 It connects with the subsegmental duct, 

⏬

leads to the  segmental duct, and 

⬇️

this to the collecting (lactiferous) duct, which empties

⏬

A fusiform dilation located beneath the nipple  between the collecting and segmental ducts is known as the lactiferous  sinus (Fig. 36.1). 

⬇️

into the nipple

The large ducts  have less specialized stroma and are enveloped by a continuous and  well-developed layer of elastic tissue. 

The  development of the breast is dependent on the close interaction of  these specialized epithelial and mesenchymal tissues.

epithelium

• The entire ductal–lobular system  of the breast is lined by a specialized inner epithelial cell layer with  secretory and absorptive functions and is 

• surrounded by an outer myoepithelial cell layer.

 

Ihc 

epithelial cells	Myoepithelial cells
Pankeratin react with both epithelial and myoepithelial cells
cytokeratins (CK) 8, 18, and 19), epithelial membrane antigen (EMA)  strongly with the apical region of active secretory  cells mammaglobin   GCDFP-15, and  GATA3.	high-molecular-weight (HMW) cytokeratins, CK14 CK5/6 calponin,  maspin, and  smooth muscle actin  (SMA),  smooth muscle myosin heavy chain caldesmon (the latter only in the ductal portion)
	nuclear reactivity for  p63 (a member of the TP53 gene  family)  p75 neurotrophin receptor (p75NTR).

A sparse population of endocrine cells in the normal breast - chromogranin +

committed stem cell (progenitor cell)

 breast—epithelial and myoepithelial—derive from a common cell  that displays the phenotypic features of a committed stem cell (progenitor cell). 

• This cell ✔️expresses CK5 in the 

• ❌🚫absence of CK8, 18, and 19  and SMA. 

These progenitor cells are postulated to differentiate through  an intermediary cell type that is CK5+ and either CK8/18+ or SMA+. 

4,5 

The entire glandular system rests on a continuous basement  membrane. 

• This can be demonstrated with reticulin stains or 

•  ihc for laminin or type IV collagen. 

nipple 

• large collecting ducts, which open onto the surface through 5-9 orifices arranged as a central and a peripheral  group

•  numerous sebaceous glands that open independently of hair follicles, 

• and a dense fibrous stroma in which erectile smooth muscle tissue is embedded.

 Montgomery tubercles 

• are areolar protuberances, usually between 10 and 20 in number, which become  prominent during pregnancy;

•  microscopically, they are formed by the  association of a collecting (lactiferous) duct with sebaceous glands.  

The epidermis of the nipple and areola 

• resembles that of the skin elsewhere,

•  except for an increase in melanin content in the basal layer and 

• the occasional presence of clear cells known as Toker cells,  which can be mistaken for the cells of Paget disease.

•  The irregular corrugated appearance of the lactiferous sinus should not be confused  with a pathologic condition.

 In approximately 15% of individuals,  normal breast lobules are present in the nipple region.9 

wide range of “normal” appearances under hormonal influence 

1. immature and largely resting breast before puberty; proliferation is largely confined to epithelial cells

2.  the developed breast of reproductive life, which exhibits changes depending on the point in the menstrual cycle10; 

3. the actively secreting  breast of lactation (Fig. 36.3); 

4. and the involuted postmenopausal  breast. 

Pregnancy and lactation,

• all cell types: high level of proliferative activity.

• exaggerated expressions 

Nodularity	lactating adenoma
leakage of milk	milk granuloma

initiation of contraceptive therapy(only definite mammary change) 

•  development of true acini resembling those seen in the lactating breast

postmenopausal involution is seen in the TDLU 

•  involves both epithelium and specialized stroma  (Fig. 36.4); it 

• may acquire a microcystic quality. 

• Deposits of elastic tissue around the ducts (elastosis) have been reported in nearly half  of all women over 50 years of age.16 

two morphologic curiosities of the breast 

1. One is the  pregnancy-like change 

• in one or several lobules in the ❌🚫absence of pregnancy or hormonal manipulation.

• The cells have abundant  vacuolated cytoplasm, 

• the nuclei are large and sometimes apically located

•  (giving the lesion an appearance that resembles the Arias-Stella  reaction), and the 

• lumina are dilated (Fig. 36.5). 

A/w cystic hypersecretory hyperplasia  (CHH), 

2.clear cell change of the ductal or  lobular epithelium, 

• cytoplasm acquires a finely granular,  finely vacuolated, or totally clear appearance (Fig. 36.6).17,20 

The  mechanism of these two changes is unknown 

 main importance of the division of the mammary gland  unit into two major portions (ducts and lobules) resides in its relation  to diseases of this organ. As Wellings et al.21 convincingly showed  and Azzopardi22 strongly emphasized, the

•  site of origin of benign  breast disease, and most carcinomas (including those of so-called  ductal type) is the TDLU and not the large duct system. 

• large duct system is primary site of most single solitary papillomas and  of duct ectasia