SUMMARY.-On the basis of histological sections and cytological smears in 110 cases, the " reticulosarcomas " (exclusive of Ewing's sarcoma and reticulosarcomas of bone marrow) were divided into two varieties: histiocytic types and histioblastic types.The correlation between the histological and cytological evaluation was excellent in each case; only those tumours classified as histiocytic presented a continuous and abundant network of reticulin.The histioblastic type predominated in the male sex. The difference in the clinical expressions of the two varieties is not statistically significant, except as to the frequency of cutaneous lesions: 27.7% in the histiocytic type and 2 6% in the histioblastic type.While the duration of their evolution is not different, only the histioblastic type is transformed into leukaemia, which is of the " monoblastic " type: this transformation was observed in 17.5% of cases, while it was never observed in histiocytic type.

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