Extrapulmonary small cell carcinoma: a clinicopathological study with identification of potential diagnostic mimics.
OBJECTIVE
To evaluate the clinicopathological features of small cell carcinoma arising outside the lung.


RESULTS
Thirty-seven cases with a pathology diagnosis of extrapulmonary small cell carcinoma (EPSCC) were selected. The clinical notes were reviewed and tumour blocks were selected for a fresh haematoxylin and eosin (H&E) section and immunohistochemical stains. The most common tumour locations were cervix and bladder. Twenty-five cases (68%) were finally diagnosed as EPSCC, nine of which were found with coexisting non small cell carcinoma. Two cases (5%) were diagnosed as large cell neuroendocrine carcinoma (LCNEC) of the cervix. The remainder was classified as 10 poorly differentiated carcinomas (PDCs) (27%). Positive staining for thyroid transcription factor 1 (TTF-1) was noted in nine cases of EPSCC and in none of the cases of PDC (P = 0.034). Synaptophysin immunoreactivity was found in 20 cases of EPSCC and two cases of PDC with neuroendocrine differentiation (P = 0.002), as well as two cases of LCNEC. 34βE12 was positive in eight cases of SCC and two cases of PDC.


CONCLUSIONS
Based on this series, EPSCC may be overdiagnosed. Immunohistochemistry for TTF-1, used in combination with synaptophysin, may help to discriminate EPSCC from PDC.
Department of Pathology, Manchester Royal Infirmary, Manchester, UK. amquinn2003@yahoo.co.uk
Anne Marie
AM
Quinn
Fiona
F
Blackhall
Godfrey
G
Wilson
Sarah
S
Danson
Andrew
A
Clamp
Linda
L
Ashcroft
Judith
J
Brierley
Philip
P
Hasleton
D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis*; D018288:Carcinoma, Small Cell / Q000175:diagnosis* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D016708:Synaptophysin / Q000096:biosynthesis; D014157:Transcription Factors; D055815:Young Adult
D014408:Biomarkers, Tumor; D004268:DNA-Binding Proteins; D016708:Synaptophysin; C504003:TTF1 protein, human; D014157:Transcription Factors