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Case of the Week #252

20 September 2012 - Case of the Week #252

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Thanks to Dr. Shahrzad Ehdaivand, Women & Infants Hospital and Warren Alpert Medical School of Brown University, Rhode Island (USA) for contributing this case. To contribute a Case of the Week, follow the guidelines on our Case of the Week page.

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Case of the Week #252

Clinical History:

A 64 year old woman had a small irregular mass on her left breast.

Micro images:


What is your diagnosis?


Granular cell tumor


The S100 stain was diffusely positive:

Granular cell tumors at all sites derive from Schwann cells of peripheral nerves, based on immunohistochemical (Med Oral Patol Oral Cir Bucal 2011;16:e6) and ultrastructural studies. They typically occur in the oral cavity, but occasionally occur in the breast.

The tumor infiltrates in sheets/cords of polygonal bland cells with well defined cell borders and abundant granular eosinophilic cytoplasm. The nuclei are round/oval, and may have small but distinct nucleoli. The tumor may also contain nonneoplastic perineurial cells (Am J Dermatopathol 2012 Jun 3 [Epub ahead of print]). They have infiltrative margins, and may be close to small nerve bundles. Typically, there is no/rare mitotic activity, and no/mild atypia. The overlying epithelium often shows pseudoepitheliomatous hyperplasia.

Clinically and radiologically, granular cell tumors may simulate carcinoma (J Clin Med Res 2010;2:185), although they typically have benign behavior. Malignant tumors are rare (1-2%). Criteria for malignancy (all sites) include necrosis, spindling, vesicular nuclei with large nucleoli, increased mitotic activity (> 2 mitoses/10 HPF at 200x magnification), high nuclear to cytoplasmic ratio, and pleomorphism (Am J Surg Pathol 1998;22:779).

The differential diagnosis includes metastatic granular cell tumor to the breast (Oncol Lett 2012;4:63), alveolar soft part sarcoma (cells divided into packets by thin walled vessels), histiocytic tumors and granulomatous inflammation. Granular cell tumors are strongly S100+, PAS+ with diastase resistance granules and CD68+. They are negative for keratin, EMA and mucin.

Local excision is usually adequate treatment. There is a low risk of recurrence, even with positive margins (Arch Pathol Lab Med 2011;135:890). However, some benign appearing tumors do have malignant behavior.

Nat Pernick, M.D., President
and Palak Thakore, Associate Medical Editor
PathologyOutlines.com, Inc.
30100 Telegraph Road, Suite 408
Bingham Farms, Michigan (USA) 48025
Telephone: 248/646-0325
Email: NatPernick@Hotmail.com
Alternate email: NatPernick@gmail.com