[Origin and cytogenetic abnormalities of sarcoid epithelioid cells]

The sarcoid epithelioid cells are believed to be a variant of tissue macrophages, which derived from circulating monocytes in blood. Formation of monocytes and macrophages are controlled by hematopoietic growth factors, i.e; colony-stimulating factors in the bone marrow. In the presence of colony-stimulating factors and/or vitamin D3, blood monocytes can proliferate and differentiate into epithelioid cells and multinucleated giant cells. In view of the evidences that sarcoid granulomas produce colony-stimulating factors and active form of vitamin D3, these results suggest that active metabolites of vitamin D3 and colony-stimulating factors produced by sarcoid epithelioid cells, induces the differentiation and proliferation of circulating monocytes into macrophage-epithelioid cells, which in turn form sarcoid granulomas. Since sarcoidosis is a disorder of cell proliferation and differentiation, a question has been always kept in my mind whether the sarcoid granulomas are chronic inflammation per se or neoplastic in nature. Interestingly, cytogenetic studies revealed that most of the epithelioid cells were aneuploid; the chromosomal number ranged from the near-haploid to the near diploid number. In addition, The distribution of DNA content of the granuloma cells was fairly wide. Our observations raise a question whether the aneuploidy in sarcoid granulomas may be due to viral infection or exposure to carcinogens as in the case of neoplastic cells. It is also possible to speculate that the aneuploidy may be a mechanism of macrophage differentiation similar to immunoglobulin gene rearrangement in B lymphocytes. Further studies are required.(ABSTRACT TRUNCATED AT 250 WORDS)