High Grade Neuroendocrine Carcinoma (Small Cell Carcinoma) of the Breast

Supplemental Studies

Keratin reactivity is higher than reported for many other small cell neuroendocrine carcinomas
CK7/20 pattern is typical of usual breast carcinomas
Not all cases have detectable neuroendocrine markers
TTF1 has been reported in a subset of non-pulmonary small cell carcinomas of various sites
ER is not reported to be positive in small cell carcinomas of other sites (Bacchi 1997)
- This may support a breast primary
- PR is not specific in the context of neuroendocrine carcinomas

Modified from Shin 2000

CK7 and CK20 do not distinguish breast from lung adenocarcinomas but may help in the distinction from ovary, pancreas, bile duct and GI carcinomas.

CK7 and CK20 expression in carcinomas
CK7+20+	CK7-20+
Ovary mucinous 90%	Colorectal adeno 80%
Transitional cell 65%	Merkel cell 70%
Pancreas adeno 65%	Gastric adeno 35%
Cholangio 65%
Gastric adeno 40%
Excluded tumors 5% or less Carcinoid; Germ cell; Esoph squam; Head/neck squam; Hepato-cellular; Lung small cell & squam; Ovary non-mucinous; Renal adeno	Excluded tumors 5% or less Breast; Carcinoid lung; Cholangio; Esoph squam; Germ cell; Lung all types; Hepato-cellular; Ovary; Pancreas adeno; Renal adeno; Transitional cell; Uterus endometrioid
CK7+20-	CK7-20-
Ovary non-mucinous 100%	Adrenal 100%
Thyroid (all 3 types) 100%	Seminoma & Yolk Sac 95%
Breast 90%	Prostate 85%
Lung adeno 90%	Hepatocellular 80%
Uterus endometrioid 85%	Renal adeno 80%
Embryonal 80%	Carcinoid intestinal & lung 80%
Mesothelioma 65%	Lung small cell & squam 75%
Transitional cell 35%	Esoph squam 70%
Pancreas adeno 30%	Head/neck squam 70%
Cholangio 30%	Mesothelioma 35%
Excluded tumors 5% or less Colorectal adeno; Ovary mucinous; Yolk Sac; Seminoma	Excluded tumors 5% or less Breast; Cholangio; Lung adeno; Ovary; Pancreas adeno

Derived from Chu PG, Weiss LM. Histopathology 2002, 40:403-439 and other sources

Estrogen receptor (ER) and progesterone receptor (PR) are important markers for directing therapy and determining prognosis
- Current consensus is that any level of positivity should be reported as positive
Her2neu status can be determined by either immunohistology or by FISH
- The other technique can be used for borderline case

Her2neu status can be determined by either immunohistology or by FISH
- The other technique can be used for borderline cases