Granuloma formation in patients after injection of methanol extraction residue (MER-BCG)

Nine patients with advanced cancer who were receiving the methanol extraction residue of BCG (MER-BCG) intradermally or intratumorally underwent biopsies from the injected sites or from locally enlarged lymph nodes. Most preparations showed a chronic granulomatous reaction consisting of lymphocytes, histiocytes, and epithelioid cells as well as either Langhans's or foreign-body type giant cells, or both. The degree of granuloma formation and giant cell infiltration varied. In only one case did the reactions consist merely of chronic lymphocytic and histiocytic inflammation with no granuloma formation. Examination of melanoma nodules injected with MER showed, in addition to granulomas, large numbers of giant cells penetrating the tumor.