Entdifferentiation in Bronchogenic Carcinoma

Abstract

Not many years have passed since it was considered possible, in a general way, to determine the histogenesis of a primary carcinoma of the lung from its cell type. Carcinomas characterized by squamous or low columnar epithelium were attributed to the alveolar epithelium; those showing the formation of mucin, to the mucous glands of the bronchi; and those with columnar epithelium, to the mucosa of the bronchi themselves. Many of the earlier authors stressed origin from the alveolar lining cells. In the group of thirty-four cases referred to in this paper there was but one (A-1760) which gave any evidence of such an origin. In this instance the most completely differentiated portion of the tumor was found in the peripheral portion of the lung, associated with an area of fibroid pneumonia. It is probable that under such circumstances excessive regeneration of bronchioles (cells of Tripier) may give rise to malignancy in a manner entirely comparable to that by which cirrhosis carcinomatosus may arise from regenerating bile ducts. Klotz (1) and Weller (2) considered that alveolar and bronchial epithelium have a common parentage, but Fried (3) held that the so-called alveolar epithelium is of mesenchymal origin, with phagocytosis its chief function, and that it cannot possibly give rise to malignancy of epithelial type. The opinion that primary carcinoma of the lung frequently arises from the bronchial mucous glands is losing ground. Fried believes that the high degree of differentiation of these glands is against the probability of malignant change. Letulle (4) does not include such an origin in his classification. Klotz, Boyd (5), Barron (6) and others have pointed out that the production of mucin by the neoplasm cannot be used as a criterion, since this function is assumed by the bronchial mucosa also. The best proof that malignancy has arisen in glands is found in such microscopic studies as those of Barron (Case 13) and Langhans (7), showing areas of apparent change in the bronchial glands themselves. It may be noted that in neither of these cases was the neoplasm mucin-forming. A great majority of all primary carcinomas of the lung arise from bronchial mucosa, and frequently from the epithelium of a bronchus of the second to fourth order. The examination of sections from a sufficient number of well chosen blocks will practically always show an area in one of the larger bronchi with alteration and replacement of the normal epithelium, penetration and partial destruction of the cartilage plates, and partial or complete obstruction of the lumen either by neoplastic tissue or by the contraction of an atypical fibrous stroma which is more mature than that found elsewhere in the neoplasm.