Cutaneous spindle-cell pseudotumors due to Mycobacterium gordonae and Leishmania infantum. An immunophenotypic study

We report two patients with AIDS who had cutaneous spindle-cell pseudotumors caused by Leishmania infantum in one instance and by an atypical mycobacterium in the other. The lesions mimicked neoplasms with predominantly spindled macrophages, similar to those seen in the histoid variant of leprosy. This histoid reaction is known to be related to mycobacteria. To our knowledge, this is the first case of histoid reaction due to leishmania. In both cases, the histiocytic cells were positive for vimentin and desmin but negative for alpha-smooth muscle. In addition, the immunostaining by lysosyme and alpha 1 antitrypsin was positive in both and in one the S-100 protein was positive. This reaction suggests dual myofibroblast and histiocytic differentiation.