[1269] Comparison of p63 and p40 (ΔNp63) in the Diagnosis of Head and Neck Sarcomatoid Carcinoma

Justin A Bishop, Elizabeth A Montgomery, William H Westra. Johns Hopkins Hospital, Baltimore, MD

Background: Sarcomatoid carcinoma (SC) is a variant of head and neck squamous cell carcinoma that includes a mesenchymal-like spindle cell component. SCs are sometimes edematous and hypocellular, mimicking a reactive fibroblastic process. Then again, they may be hypercellular and resemble a true sarcoma. Cytokeratin immunohistochemistry (IHC) is often not helpful in resolving the differential diagnosis: SCs are often cytokeratin negative; and conversely, reactive and neoplastic mesenchymal proliferations may be focally cytokeratin positive. P63 expression is often used as a marker of squamous differentiation, but its usefulness in diagnosing SC is offset by expression in some soft tissue tumors and uncertainty regarding p63 expression in reactive stromal proliferations. P40 is an antibody that recognizes ΔNp63 – a p63 isoform that is highly specific for squamous differentiation. As such, p40 IHC could enhance the diagnosis of SCs.
Design: IHC for both p63 and p40 was performed on 35 head and neck SCs. All of the SCs were biphasic tumors that included a component of conventional squamous cell carcinoma. In addition, 40 reactive stromal proliferations and 139 soft tissue neoplasms were tested. IHC was performed on whole slides (n=110) or tissue microarrays (n=104).
Results: The results are summarized in Table 1. Of the 35 SCs, p63 staining was noted in 20 (57%) cases, and p40 staining was present in 18 (51%) cases. Staining was focal (i.e., <5% cells) for p63 and p40 in 5 and 3 cases, respectively. P63 staining was also observed in 40/139 (29%) soft tissue neoplasms and in 12/40 (30%) reactive stromal proliferations. In contrast, p40 staining was observed in only 5/139 (4%) soft tissue neoplasms and 0/40 reactive stromal proliferations.

Table 1
 p63 (%)p40 (%)
Sarcomatoid carcinoma20/35 (57)18/35 (51)
Reactive stromal proliferations12/40 (30)0/40 (0)
Soft tissue neoplasms40/139 (29)5/139 (4)
Angiosarcoma3/10 (30)1/10 (10)
Cellular schwannoma2/3 (67)0/3 (0)
Epithelioid sarcoma1/14 (14)1/14 (14)
IMT2/13 (15)1/13 (8)
Kaposi sarcoma1/26 (4)0/26 (0)
LG fibromyxoid sarcoma5/9 (56)0/9 (0)
Leiomyosarcoma5/15 (33)0/15 (0)
MFH13/33 (39)1/33 (3)
MPNST2/5 (40)0/5 (0)
Rhabdomyosarcoma4/9 (44)1/9 (11)
Synovial sarcoma3/8 (38)1/8 (13)



Conclusions: Compared to p63, p40 expression is less likely to be encountered in reactive and neoplastic mesenchymal lesions and thus represents a more specific marker of SC. When it comes to the diagnostic interpretation of spindle cell lesions of the head and neck, p40 staining provides compelling evidence of SC while p63 staining must be viewed with more caution.
Category: Head & Neck

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 195, Wednesday Morning

 

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