Calretinin staining facilitates differentiation of olfactory neuroblastoma from other small round blue cell tumors in the sinonasal tract.
OBJECTIVE
Olfactory neuroblastoma (ONB) is an uncommon malignant tumor of the sinonasal tract and has a wide histologic differential diagnosis that includes other small round blue cell tumors (SRBCTs). Even with the use of immunohistochemistry (IHC), the correct diagnosis may be difficult, especially in small biopsies. The purpose of this study is to determine the usefulness of calretinin and p63 as an aid to distinguish ONB from other sinonasal SRBCTs.


METHODS
IHC staining for calretinin and p63 was performed on 21 specimens diagnosed as ONB and on 42 other sinonasal SRBCTs. Specimens were retrieved from the files of the QEII HSC, Halifax and UHN, Toronto.


RESULTS
All but 1 ONB (20 of 21) showed calretinin staining, with 15 of 21 showing staining in >75% of the tumor area and 18 of 21 showing moderate-to-strong staining intensity. Only pituitary adenomas (3 of 3) and a single case of small cell carcinoma, neuroendocrine type (1 of 2), showed a similar staining pattern. None of the ONBs showed staining for p63. P63 was positive in all cases of nonkeratinizing squamous cell carcinoma (2 of 2) and in single cases of mantle cell lymphoma (1 of 1) and poorly differentiated neuroendocrine carcinoma (1 of 1); however, it inconsistently stained diffuse large B-cell lymphoma (4 of 5), extranodal NK/T-cell lymphoma, nasal type (1 of 4), sinonasal undifferentiated carcinoma (1 of 6), and Ewing sarcoma/primitive neuroectodermal tumor (2 of 6).


CONCLUSIONS
Calretinin appears to be a useful marker to distinguish ONBs from other SRBCTs of the sinonasal tract, particularly when staining is moderate/strong and extensive. The calretinin-positive, p63-negative phenotype is fairly specific for ONB. The addition of these 2 IHC stains may aid in the diagnosis of sinonasal SRBCTs that are poorly differentiated, have inconclusive conventional IHC, or are found in small biopsies.
Department of Pathology, Capital District Health Authority, Dalhousie University, Halifax, NS, USA.
Jill C
JC
Wooff
Ilan
I
Weinreb
Bayardo
B
Perez-Ordonez
James Fergall
JF
Magee
Martin J
MJ
Bullock
D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis*; D064032:Calbindin 2; D003937:Diagnosis, Differential; D018304:Esthesioneuroblastoma, Olfactory / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis; D008875:Middle Aged; D009296:Nasal Cavity / Q000473:pathology; D009669:Nose Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D064030:S100 Calcium Binding Protein G / Q000096:biosynthesis*; D055815:Young Adult
D014408:Biomarkers, Tumor; C576764:CALB2 protein, human; C081876:CKAP4 protein, human; D064032:Calbindin 2; D008565:Membrane Proteins; D064030:S100 Calcium Binding Protein G