Small cell carcinoma of the prostate

Definition

A rare tumour of the prostate with a small cell morphology resembling that seen in small cell carcinoma of the lung. Prostate is one of the least uncommon primary sites for extra-pulmonary small cell carcinoma.

Epidemiology

Small cell carcinoma constitutes not more than 2% of all prostatic carcinomas. Patients range from the fifty to tenth decade with a mean of about 70 years.

Clinical features

Many patients have a prior history of adenocarcinoma of the prostate6. The serum PSA varies from normal to markedly raised.

Histopathology

The majority of cases show an oat cell morphology. The cells are small and uniform with dense round or oval nuclei, finely granular chromatin, inconspicuous nucleoli and little cytoplasm. A minority of cases are of intermediate cell type with larger cells having more cytoplasm and larger nuclei, some with nucleoli. Giant cells may be present. The cells may form Indian files or rosettes. The stroma may be desmoplastic or myxoid. Necrosis is common. The small cell carcinoma may be admixed with an adenocarcinomatous component.

Immunohistochemistry

	Prostatic small cell carcinoma	Gleason pattern 5b prostate adenocarcinoma
PSA	14/735, 3/187	10/107
Prostate-specific acid phosphatase	4/177	10/107
Prostein, P501S	17/615
P504S	8/177	10/107
Prostate-specific membrane antigen	15/595
TTF-1	4/4(using Dako clone)1, 5/52, 0/33, 1/3(using clone 8G7G3/1)4, 23/44(using clone 8G7G3/1)5, 15/18(said to have used Dako clone 8E7E3/1!)7	0/107
CD56	12/135, 15/187	0/107
Chromogranin	33/445, 11/187	0/107
Synaptophysin	27/325, 16/187	4/107
NSE	17/205
Somatostatin	3/187	0/107
Calcitonin	3/187	2/107
Bombesin	14/167	1/107
Androgen receptor	3/187	9/107
Oestrogen receptor	0/137	1/107
Progesterone receptor	0/137	2/107
p63	4/177	1/107
AE1/AE3	15/167	7/107
Cam5.2	13/18(often in a dot-like pattern)7	9/107
CK7	7/187	3/107
CK20	2/187	1/107
34bE12	6/177	0/107
CD117	17/187	3/107
bcl-2	18/187	2/107
EGFR	8/117	4/107
Her2	0/177	0/107

Differential diagnosis

Oat cell variant:

metastatic small cell carcinoma of the lung.
Lymphoma

Intermediate cell variant:

poorly differentiated adenocarcinoma of the prostate: glandular differentiation is lacking but the cells are larger, with more cytoplasm and a lack of nuclear moulding; nuclei have coarse chromatin and nucleoli.
large cell neuroendocrine carcinoma.

Management

Anti-androgen therapy is ineffective.

Prognosis

This is an aggressive tumour, similar to small cell carcinoma of the lung.

References

1 Agoff SN et al. Thyroid transcription factor-1 is expressed in extrapulmonary small cell carcinomas but not in other extrapulmonary neuroendocrine tumours. Mod Pathol 2000;13:238-242. FULL TEXT

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 Ordonez NG. Value of thyroid transcription factor-1 immunostaining in distinguishing small cell lung carcinomas from other small cell carcinomas. Am J Surg Pathol 2000;24:1217-1223.

4 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 FULL TEXT

5 Wang W,Epstein JI Small cell carcinoma of the prostate. A morphologic and immunohistochemical study of 95 cases. Am J Surg Pathol 2008; 32:65-71

6 Nadig SN, Deibler AR, El Salamony TM, et al. Small cell carcinoma of the prostate: an underrecognized entity. Can J Urol 2001; 8:1207-10

7 Yao JL, Madeb R, Bourne P, et al. Small cell carcinoma of the prostate: an immunohistochemical study. Am J Surg Pathol 2006; 30:705-12

Yao JL, Huang J, di Sant'Agnese. Small cell carcinoma of the prostate. Diagnostic Histopathology 2008; 14:117-121