Benign Transport

Isolated Tumor Cells (ITC)

Age

Women of any age who undergo lymph node evaluation as part of breast cancer staging

Women of any age who undergo lymph node evaluation as part of breast cancer staging

Location

Subcapsular sinus of lymph node

Lymph node sinuses or parenchyma

Imaging findings

None or varying degrees of radionucleotide uptake identifying sentinel location

None or varying degrees of radionucleotide uptake identifying sentinel location

Etiology

Mechanical disruption and displacement secondary to prior breast biopsy

Lymphatic spread from mammary carcinoma

Histology

1. 
   

   Single or small clusters of epithelial cells in subcapsular location (Figs. 9.1.1 and 9.1.2)

   
   
2. 
   

   Pyknosis and prominent degenerative changes of the epithelium (Fig. 9.1.3)

   
   
3. 
   

   Lack of stromal response

   
   
4. 
   

   Hemosiderin, red blood cells (RBCs), histiocytes, cellular debris, and giant cells (Fig. 9.1.3)

   
   
5. 
   

   Most often occurs following biopsy of papillary or micropapillary lesions; epithelial cell clusters in lymph node sinuses resemble previously biopsied lesion

1. 
   

   Small clusters of epithelial cells present within the substance of lymph node and/or subcapsular sinus, usually with some associated stromal response (Figs. 9.1.4 and 9.1.5)

   
   
2. 
   

   Solid nests or single cells, some with intracytoplasmic inclusions

   
   
3. 
   

   Epithelial cells lack degenerative changes (Fig. 9.1.5)

   
   
4. 
   

   Contiguous cells span a distance no larger than 0.2 mm and contain fewer than 200 tumor cells (Fig. 9.1.6)

   
   
5. 
   

   Lack of associated hemosiderin-laden macrophages, RBCs, and giant cells

Special studies

None

None, but cytokeratin immunohistochemistry may be helpful when the tumor cells are widely dispersed

Treatment

Axillary lymph node dissection not indicated; treatment based on primary tumor characteristics

Axillary lymph node dissection not indicated; treatment based on primary tumor characteristics

Clinical implication

Lymph nodes that contain epithelial cell clusters resulting from benign transport are classified as pN0

Lymph node classified as pN0 (itc+)

ITC After Neoadjuvant Chemotherapy

Micrometastasis After Neoadjuvant Chemotherapy

Age

Women of any age who undergo lymph node evaluation as part of breast cancer staging

Women of any age who undergo lymph node evaluation as part of breast cancer staging

Location

Lymph node sinuses or parenchyma

Lymph node sinuses or parenchyma

Imaging findings

None or varying degrees of radionucleotide uptake identifying sentinel location

None or varying degrees of radionucleotide uptake identifying sentinel location

Etiology

Lymphatic spread from mammary carcinoma

Lymphatic spread from mammary carcinoma

Histology

1. 
   

   Small clusters of epithelial cells present within the substance of a lymph node and/or subcapsular sinus, usually with some associated fibrosis and lymphoid depletion characteristic of neoadjuvant chemotherapy effect (Fig. 9.2.1)

   
   
2. 
   

   Epithelial cells may show vacuolated cytoplasm (Fig. 9.2.2)

   
   
3. 
   

   Cytokeratin immunohistochemistry shows scattered neoplastic cells, numbering fewer than 200 (Fig. 9.2.3)

1. 
   

   Prominent sclerosis of lymph node with lymphoid depletion (Fig. 9.2.4)

   
   
2. 
   

   Small clusters of epithelial cells are present within the substance of the residual nodal tissue and/or subcapsular sinus measuring more than 0.2 mm but not more than 2.0 mm (Fig. 9.2.5)

   
   
3. 
   

   Stromal response within the residual lymph node is limited (Fig. 9.2.5)

Special studies

None, but cytokeratin may help with classification when the tumor cells are widely dispersed

None

Treatment

None, complete axillary dissection not indicated; additional treatment based on residual primary tumor characteristics

Complete axillary dissection not indicated if other sampled lymph nodes are negative for macrometastasis; treatment and prognosis are based on primary tumor characteristics

Clinical implication

Lymph node classified as ypN0 (itc+)

Classified as ypN1mi

Micrometastasis

Macrometastasis

Age

Women of any age who undergo lymph node evaluation as part of breast cancer staging

Women of any age who undergo lymph node evaluation as part of breast cancer staging

Location

Lymph node sinuses or parenchyma

Lymph node sinuses or parenchyma

Imaging findings

None or varying degrees of radionucleotide uptake identifying sentinel location

None or varying degrees of radionucleotide uptake identifying sentinel location

Etiology

Lymphatic spread from mammary tumor

Lymphatic spread from mammary tumor

Histology

1. 
   

   Small clusters of epithelial cells present within the substance of the lymph node and/or subcapsular sinus (Fig. 9.3.1)

   
   
2. 
   

   Solid nests or single cells, some with intracytoplasmic inclusions (Fig. 9.3.2)

   
   
3. 
   

   At least one focus of metastatic carcinoma or closely approximated clusters of carcinoma cells measuring more than 0.2 mm but not more than 2.0 mm, in nodal substance with or without involvement of subcapsular sinus, usually with some associated stromal response (Fig. 9.3.3)

1. 
   

   Focus of metastatic carcinoma measuring more than 2.0 mm, present in nodal substance (Fig. 9.3.4)

   
   
2. 
   

   Alteration of lymph node architecture (Figs. 9.3.4, 9.3.5)

   
   
3. 
   

   Usually associated with stromal response (Fig. 9.3.5)

Special studies

None routinely

None routinely. In borderline cases, hematoxylin and eosin (H&E) levels may help to establish presence of a more extensive lesion; accurate size determination (e.g., invasive lobular carcinoma) may be facilitated by cytokeratin immunohistochemistry

Treatment

Axillary node dissection not indicated if other sampled lymph nodes are negative for macrometastasis; treatment based on primary tumor characteristics

Complete axillary lymph node dissection frequently performed

Clinical implication

Classified as pN1mi

Single macrometastasis classified as pN1a; establishes propensity for distant metastasis