[1947] Pulmonary Sarcomatoid Carcinoma – Immunohistochemical Study of 35 Cases with Emphasis on the Utility of Napsin

Simone BSP Terra, Marie Christine Aubry, Eunhee S Yi, Jennifer M Boland. Mayo Clinic, Rochester, MN

Background: Lung sarcomatoid carcinomas (SC) present a challenging differential diagnosis. Immunohistochemical (IHC) markers are often used in the distinction between SC and tumors with overlapping morphologic features, including sarcomatoid mesothelioma and sarcomas. Napsin has recently emerged as a marker of lung adenocarcinoma, and some studies have shown it to have superior sensitivity and specificity than the alternative marker TTF-1. However, literature on napsin expression in SC is very limited. The goal of this study is to evaluate the usefulness of napsin in addition to the standard IHC panel often applied to pulmonary sarcomatoid malignancies.
Design: Cases of SC surgically treated at Mayo Clinic were evaluated morphologically, and with IHC for napsin, TTF-1, Oscar keratin, CAM5.2, AE1/3, desmin, SMA, S-100, CK5/6, calretinin, D2-40, and WT-1. Cases were excluded if they were keratin negative or were suspected mesothelioma.
Results: The 35 patients were 24 men and 11 women, with a mean age of 70 years (range 46-93). Cases consisted of 26 pleomorphic carcinomas, 5 spindle cell carcinomas, 3 carcinosarcomas and 1 giant cell carcinoma. 20 cases had an identifiable non-small cell component: 14 adenocarcinoma, 3 squamous, 2 large cell, and 1 adenosquamous carcinoma. All cases were positive for at least one keratin, although staining was often focal: AE1/3 was positive in all 35 cases, Oscar in 33 cases (94%), and CAM5.2 in 31 cases (89%, weaker and more focal staining). Napsin was positive in 14 cases (40%): 8 diffuse, 3 focal and 3 rare positive cells. TTF-1 was positive in 21 cases (60%): 14 diffuse, 3 focal and 4 rare positive cells. No cases were napsin positive and negative for TTF-1. While no tumors showed diffuse positivity of multiple mesothelial markers, some cases showed some staining for calretinin (12 cases, 34%), WT-1 (6 cases, 17%, 1 diffuse), D2-40 (5 cases, 14%, 2 diffuse), and CK 5/6 (9 cases, 26%, 2 with squamous morphology). Mesenchymal markers were also sometimes positive, although the staining was usually very focal, including S-100 (4 cases, 11%, including 2 carcinosarcomas with cartilage), desmin (4 cases, 11%, including one carcinosarcoma with rhabdomyoblasts), and SMA (6 cases, 17%, 1 diffuse).
Conclusions: TTF-1 is more sensitive than napsin in the detection of SC, and no cases were positive for napsin but negative for TTF-1. CAM5.2 is less sensitive than AE1/3 and Oscar, and often shows more focal staining. Use of an IHC panel is important in evaluation of sarcomatoid lesions of the lung and pleura, since isolated mesothelial and mesenchymal markers can be expressed in SC.
Category: Pulmonary

Monday, March 4, 2013 1:00 PM

Poster Session II # 298, Monday Afternoon


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