THE MAST CELLS 



Two types of mast-cell tumour have been reported in mice. The first 

 consists of single or multiple nodules in the skin of mice which have been 

 painted with a carcinogen, one such tumour (the '3187 transplantable mast- 

 cell sarcoma') proving sufficiently autonomous to be carried as a transplant 

 for several generations before it eventually died out; a more recent tumour is 

 still available (Dunn and Potter, 1957). A similar transplantable mastocytoma 

 has been derived from a mouse subjected to ionizing radiation (Furth et al, 

 1957). The second type, more properly described perhaps as a diffuse masto- 

 cytosis, is seen occasionally in old Strain A mice in which mast cells infiltrate 

 the internal organs, especially the spleen. In discussing the aetiology of the 

 condition Deringer and Dunn (1947) record that a high mast-cell content of 

 the spleen appears to be a common feature in old mice of this strain. 



Spontaneous single or multiple mast-cell tumours are by no means un- 

 common in certain domestic animals (cf. Head, 1953). Sabrazes and Lafon 

 (1907) describe a tumour consisting predominantly of mast cells and eosinophils 

 which appeared on the lip of a horse following injury. Sabrazes, Muratet and 

 Antoine (1908) also record a pigmented tumour on the eyelid of a cat whose 

 spleen was distended with mast cells and plasma cells. We have recently had 

 the opportunity of examining several types of mastocytoma in domestic 

 animals, including a cow with multiple mastocytomas of the skin (Head et ah 

 1959, and see Chapter X). 



Subcutaneous mast-cell tumours are seen most frequently in dogs (Bloom, 

 1942; Mulligan, 1948; Head, 1953). According to Bloom, solitary benign 

 mastocytomas in dogs consist of densely packed islands of well differentiated 

 mast cells separated by strands of almost avascular stroma. More rarely the 

 tumours are multiple and malignant, the neoplastic cells often containing one 

 or more varieties of curious cytoplasmic inclusion. In dogs with multiple 

 tumours malignant mast cells may also be found in liver, spleen, lung, marrow 

 and in the regional lymph nodes, the liver and lymph nodes also often showing 

 connective tissue hyperplasia. Bloom concludes (p. 674) k It seems reasonable 

 to assume that the neoplastic mast cells arose from proliferation of the pre- 

 existing tissue mast cells, and in this process lost their polymorphism and acquired 

 a generally more oval or spherical form and a larger, relatively vesicular 

 nucleus. The transformation was accomplished in the solitary tumors by 

 amitotic activity, as evidenced by binucleation and occasionally constricted, 

 elongated nuclei, and in the multiple tumors by mitoses and amitoses'. Malig- 

 nant cells from mast-cell tumours in dogs and cattle have been successfully 

 grown in tissue culture (Paff, Bloom and Reilly, 1947; Paff, Montagna and 

 Bloom, 1947; MacDougall, 1954). 



4. The mast cell in carcinogenesis. Very early in the study of experi- 

 mental carcinogenesis a striking mast-cell reaction was noted in the skin of 



26 



