THE ERGASTOPLASM IN THE MAMMARY GLAND AND ITS TUMOURS 1 85 



B cells correspond to Caspersson and Santesson's original description, and 

 refinement of criteria allows better detection, better study of their repar- 

 tition and lays stress on the importance of all intermediate aspects be- 

 tween the two A and B extreme types (Transitional T cells of Gusberg 

 et al. [18] Towell [22] (Fig. 14). 



Neither the B (Fig. 10) nor the intermediate (Fig. 14) type of cell 

 which constitute the bulk of the tumour will concern us in the following 

 description because they have been referred to in the first part of this 

 paper and it has been shown that their ergastoplasm is not particularly 

 developed and not typically organized. 



The A type of cell, on the contrary will be described in detail because 

 of its richness in ergastoplasm which corresponds to the high content of 

 cvtoplasmic RNA found with the ultraviolet absorption technique. Their 

 ultrastructural appearance is striking (Figs. 12, 13, 15, 16). Usually 

 smaller than adjacent cells they are often sharply edged, and when not 

 at the periphery, wedged in between the other cells. They contrast with 

 these by the remarkable density of both their nucleus and their cytoplasm. 



The nucleus is characteristic, its chromatin is coarse and mottled, its 

 limits festooned. In the cytoplasm, the ergastoplasm is densely packed 

 and present either in its unorganized form of numerous RNP-granules or 

 organized in a lamellar system. This latter organization, however, is distinct 

 from that of the normal array mentioned above and related to physiological 

 secretion. No regularity is found in the repartition of the RNP-granules 

 along the membranes and the parallel arrangement of these is not 

 regular either (Figs. 13, 15). Distension of the interlamellar space is often 

 conspicuous and in many A types of cells is so marked that a lace-like 

 pattern is outlined (Fig. 16). These cells appear vacuolated and since 

 their nuclei are often shrunken as well, they easily evoke the picture 

 of a degenerating necrotic cell. It is therefore impossible, on an ultra- 

 structural basis to decide whether the typical A type of cell corresponds 

 to a young, still undifiPerentiated element as believed by most or whether 

 it is not simply a necrotic cell. 



It is not the place here to argue about the matter. The important notion 

 is that two different types of cells at least have been detected with spectro- 

 photometric and staining techniques and are detected again in the electron 

 microscope. Whether thev are absolutely identical with the A and B cells 

 of Caspersson and Santesson and whether they represent young or aged 

 elements is fundamental only to explain their significance. If this could 

 be imderstood, it is possible that great advances would be achieved in 

 ultrastructural cytology of cancer because the great development of A 

 cells in some neoplasms represents the only ultrastructural characteristic 

 common to different types of cancer. Indeed there is no difference between 

 some A type cells observed in adenocarcinoma of the breast and those 



