Neuroendocrine Tumours of the Breast

Epidemiology and Etiology:

• < 1 % of breast carcinomas

Common sites:

Gross features:

Histologic features:

• Morphologic features similar to those of GI tract and lung
• Presence of DCIS with similar cytologic features is supportive of origin in the breast
• NET, WD:
• Densely cellular
• Solid nests and trabeculae separated by delicate fibrovascular stroma
• Spindle to plasmacytoid to large clear cells
• NET, PD:
• Morphologically indistinguishable from lung primaries
• In situ component with same cytologic features may be detected
• Lymphatic tumour emboli frequently

Immunophenotype:

Marker:	Sensitivity:	Specificity:
Synaptophysin	~50% of PD
Chromogranin	~50% of PD
NSE	100% of poorly differentiated / small cell carcinomas of the breast
ER	Majority of WD > 50% of PD
PR	Majority of WD > 50% of PD

Molecular features:

Other features:

• Metastasis should be excluded before making a definite diagnosis

References:

• WHO 2012 blue book