What is the anatomic pathology of granular cell tumors (GCTs)?

Updated: Nov 12, 2020
  • Author: Vladimir O Osipov, MD; Chief Editor: E Jason Abel, MD  more...
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Gross features include pale white/yellow, nonencapsulated, and variably (well to poorly) circumscribed nodules with solid, fleshy cut surfaces that are devoid of liquefaction, necrosis, or bleeding. The overlying skin or mucosa is thickened and may have a cobblestone appearance. [16]

Microscopic features of benign granular cell tumors are remarkably uniform, regardless of the site. Granular cell tumors are sometimes located near a nerve twig, usually within the perineurium, and are variably circumscribed at the periphery. Approximately half of all granular cell tumors have poorly defined or infiltrative margins. The nodules are composed of large polyhedral cells arranged in sheets, nests, lobules, or trabeculae and are surrounded by variable stroma. A reticulin framework may be around individual cells or small groups of cells. Occasionally, granular cell tumors are extensively collagenized.

The tumor cells have abundant granular eosinophilic cytoplasm with centrally located vesicular or pyknotic nuclei. Markedly enlarged lysosomes in tumor cells may be observed as eosinophilic globules surrounded by a clear halo; some are extruded from cells and may be phagocytosed by histiocytes. In such cases, they are termed angulate bodies. Usually, the granules stain positive with periodic acid-Schiff (PAS) staining and are resistant to diastase. They also stain with Sudan black B and are magenta in trichrome preparations. Multinucleation, plentiful mitotic activity, nuclear pleomorphism, and prominent nucleoli are uncommon features. Squamous epithelium overlying the peripheral superficial lesions exhibits acanthosis and pseudoepitheliomatous hyperplasia.

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