The sarcoid granuloma: ‘epithelioid’ or ‘lymphocytic-epithelioid’ granuloma?

BACKGROUND This study aims to analyze the structure and quantities of cellular elements in sarcoid granulomas. METHODS We investigated 34 transbronchial lung biopsy samples obtained from 34 sarcoid patients. The quantity and composition of the cellular elements inside a granuloma were determined by the quantitative stereometry method, employing the numerical density as a stereological method. RESULTS A total of 102 sarcoid granulomas were analyzed. The central part of all granulomas was occupied by epithelioid cells. Besides these, giant cells, lymphocytes, macrophages and plasma cells were also seen. The mean numerical density of all the cells in the central part of a sarcoid granuloma was 111,751 mm-3. Lymphocytes prevailed in number, exceeding the total count of all other cells. With a mean numerical density of 74,321 mm-3, lymphocytes were twice as numerous as both epithelioid cells and macrophages with a mean numerical density of 37,193 mm-3. CONCLUSIONS Lymphocytes are the predominant cell type in the central part of a sarcoid granuloma, significantly exceeding both epithelioid cells and macrophages in number, raising the question if the term "epithelioid granuloma", routinely used to designate sarcoid granulomas, is correct, or if it would be more logical to call them "lymphocytic-epithelioid granulomas" instead. TRIAL REGISTRATION This study was supported by the Serbian Ministry of Science and Environmental Protection Grant Number 175006/2011.