Granular cell changes can be observed in a variety of benign and malignant tumors, and are seen more commonly in granular cell tumors, which in about 5% of cases develop in the breast. Granular cells also have been observed in sites of previous trauma, such as surgery, and are found to be inflammatory reactions of histiocytic origin.
We investigated, morphologically and immunohistochemically, 2 granular cell lesions occurring in mastectomy scars after surgery for carcinoma. Both lesions were composed of strands and nests of large granular cells, haphazardly set in a background of fibrous tissue, with sparse inflammatory infiltrates. Several tortuous hypertrophic nerve bundles were also embedded in the fibrous tissue. A few of these nerve bundles showed degenerative changes and contained granular cells. Immunohistochemically, granular cells were positive for S100 protein, neuron-specific enolase, vimentin, and CD68 antigen.
We consider these proliferative lesions of peripheral nerves to have the features of both granular cell tumor and traumatic neuroma. These cases indicate that traumatic neuroma can undergo extensive granular cell changes and constitute a previously unrecognized entity, which we provisionally label granular cell traumatic neuroma. Granular cell traumatic neuroma has to be taken into consideration when evaluating lesions occurring at mastectomy scars and should be differentiated from malignant tumors with granular cells, such as apocrine carcinoma and alveolar soft part sarcoma.