Small cell carcinoma of the breast

Epidemiology

Primary small cell carcinoma of the breast is exceedingly rare, in one study comprising 0.3% of all breast carcinomas7. The reported cases occurred in middle aged to elderly women6.

Histology

The tumour has infiltration margins. The cells resemble those of small cell carcinoma of the lung or other sites, with small nuclei, nuclear moulding, scant cytoplasm, finely granular chromatin and inconspicuous nucleoli. The cells may form solid, trabecular or alveolar patterns. Crush artefact and an Azzopardi effect may occur6.

Small cell carcinoma may be combined with conventional intraduct, invasive ductal or lobular carcinoma.

Immunohistochemistry


	primary small cell carcinoma	carcinoma with endocrine features	invasive ductal carcinoma
AE1/AE3	1/21, 10/10(all cases strongly positive)6, 2/27	5/57	5/57
34bE12	0/27	2/5(equivocal)	5/5
Cam5.2	1/21, 8/106, 2/27	5/57	5/57
CK7	8/106, 2/2(equivocal in one case)7	5/57	5/57
CK19	7/96, 2/27	5/57	5/57
CK20	0/106, 0/27	0/57	5/5(3 cases equivocal)7
EMA	2/27	5/57	5/57
CEA	2/27	3/57	2/57
Chromogranin	1/21, 4/106, 2/27	5/57	0/57
Synaptophysin	1/21, 5/106, 2/27	5/57	5/57
NSE	10/10(all cases strongly positive)6, 2/27	5/57	5/57
CD56	7/96, 2/27	3/57	4/57
S100	1/27	4/57	2/57
Grimelius	2/27	4/57	0/57
CD57	3/96, 2/27	5/57	5/57
Calcitonin	3/106, 2/27	5/57	5/57
Gastrin-releasing peptide	2/96
Neurofilament	0/96
Somatostatin	0/96
Serotonin	0/96
CD10	0/27	0/57	5/57
CD99	1/2 (focal)1
Oestrogen receptor	0/21, 6/106, 1/27	5/57	4/57
Progesterone receptor	0/21, 5/106, 1/27	5/57	4/57
bcl-2	10/106, 2/27	5/57	5/57
TTF-1	1/12, 1/23, 2/104, 1/15, 1/26, 1/35, 2/27, 0/18, 0/19	5/57	4/57
E-cadherin	11/114, 1/27	5/57	5/57
N-cadherin	2/27	5/57	3/57
Vimentin	4/96, 0/57	5/57	5/57
Her2/neu	0/106, 1/27	5/57	4/57
Ki-67 index	76%1, 95%1
p53	negative1, 6/96, 2/27	4/57	3/57

Differential diagnosis

Lobular carcinoma is negative for E-cadherin, in contrast to the positivity of small cell carcinoma.

Prognosis

In the largest series, although 2 of 9 patients developed metastases, all 9 were alive with follow up of 3 to 35 months6.

References

1 Hoang, M. P., Maitra, A., Gazdar, A. F., Albores-Saavedra, J. Primary mammary small-cell carcinoma: a molecular analysis of 2 cases. Human Pathol 2001;32:753-757.

2 Kaufmann O & Dietel M. Expression of thyroid transcription factor-1 in pulmonary and extrapulmonary small cell carcinomas and other neuroendocrine carcinomas of various primary sites. Histopathology 2000; 36: 415-420

3 Cheuk W et al. Immunostaining for thyroid transcription factor-1 and cytokeratin 20 aids in the distinction of small cell carcinoma from Merkel cell carcinoma, but not pulmonary from extrapulmonary small cell carcinoma. Arch Pathol Lab Med 2001;125:228-231. (supplemented by personal communication).

4 Shin SJ, DeLellis RA,Rosen PP. Small cell carcinoma of the breast--additional immunohistochemical studies. Am J Surg Pathol 2001; 25:831-2

5 TTF-1 Barbareschi, M., C. Roldo, et al. (2004). "CDX-2 homeobox gene product expression in neuroendocrine tumors: its role as a marker of intestinal neuroendocrine tumors." Am J Surg Pathol 28(9): 1169-76.

6 Shin SJ, DeLellis RA, Ying L, et al. Small cell carcinoma of the breast: a clinicopathologic and immunohistochemical study of nine patients. Am J Surg Pathol 2000; 24:1231-8

7 Yamamoto J, Ohshima K, Nabeshima K, et al. Comparative study of primary mammary small cell carcinoma, carcinoma with endocrine features and invasive ductal carcinoma. Oncol Rep 2004; 11:825-31

8 Kitakata H, Yasumoto K, Sudo Y, et al. A case of primary small cell carcinoma of the breast. Breast Cancer 2007; 14:414-9 FULL TEXT

9 Mariscal A, Balliu E, Diaz R, et al. Primary oat cell carcinoma of the breast: imaging features. AJR Am J Roentgenol 2004; 183:1169-71 FULL TEXT