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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?































Diagnosis:

Granular cell tumor

Discussion:

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.
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Bingham Farms, Michigan (USA) 48025
Telephone: 248/646-0325
Email: NatPernick@Hotmail.com
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