Inflammatory sarcomatoid carcinoma of the lung: Report of three cases and clinicopathologic comparison with inflammatory pseudotumors in adult patients

Abstract

Although the capacity for some pulmonary carcinomas to mimic sarcomas is well recognized, their potential resemblance to selected benign lesions of the lung is currently underappreciated. The authors herein report three examples of sarcomatoid bronchogenic carcinoma with a deceptively bland appearance and an investment of reactive inflammation, such that they resembled pseudotumors histologically. These lesions occurred in two men and one woman who were 44, 61, and 63 years old, respectively, at diagnosis. All patients presented with a productive cough, hemoptysis, or chest pain. Their pulmonary masses were irregularly marginated radiographically, and ranged in size from 2.5 to 5.5 cm. Two were treated with lobectomy, and one underwent a wedge excision, followed by radiotherapy to the thorax. Despite these measures, each patient with inflammatory sarcomatoid carcinoma (ISC) died of disease or is likely to do so. Microscopically, ISCs were composed of uniform spindle cell proliferations with only modest nuclear pleomorphism, limited mitotic activity, and an arrangement in fascicles, storiform configurations, or haphazard arrays. Lymphocytes and plasma cells were interspersed throughout each of them, and keloidal stromal collagen was apparent internally in two examples. Two of the neoplasms also invaded pulmonary blood vessels or bronchi. A comparison group of 10 adults with pulmonary inflammatory pseudotumors (IPs) of the fibrous histiocytoma type shared several clinical attributes with ISC and showed closely similar histological features, except that the IPs lacked mitoses and invasiveness, and contained xanthoma cells or multinucleated elements in some cases in this series. Immunohistochemical analyses showed consistent dissimilarities between ISC and IP; keratin and epithelial membrane antigen were present in ISC but not IP, whereas actin was observed only in the proliferating spindle cells of IP. In summary, the potential clinicopathologic overlap between ISC and IP suggests that caution should be exercised in the separation of these two lesions. In particular, it is unwise to attempt to make this distinction in an intraoperative frozen section setting.