General
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• Tumor whose cells have granular eosinophilic cytoplasm and bland small nuclei

Epidemiology
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• Uncommon, <1 per 1000 malignancies (J Ultrasound Med 2008;27:467)
• More common in women in 40's; may be more common in African-American women

Sites
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• Usually inner quadrants of breast

Etiology
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• Appears to derive from Schwann cells of peripheral nerves (at all sites)

Clinical features
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• Resembles invasive carcinoma clinically, but almost always benign
• Xray: suggestive of malignancy due to apparent infiltration

Case reports
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• 22 year old woman with granular cell tumor of the breast (Cases J 2009;2:8551)
• 47 year old woman with outer quadrant breast mass (Arch Pathol Lab Med 2003;127:1525)
• 55 year old woman with granular cell tumour of the pectoral muscle mimicking breast cancer (Cases J 2008;1:142)
• 55 and 67 year old women with granular cell traumatic neuroma (Arch Pathol Lab Med 2000;124:709)
• 57 year old woman with colocalized granular cell tumor and infiltrating ductal carcinoma of the breast (Arch Pathol Lab Med 2002;126:731)
• 64 year old woman with small irregular mass on her left breast (Case of the Week #252)
• Malignant granular cell tumor (Arch Pathol Lab Med 1992;116:206)

Treatment
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• Local excision

Clinical images
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Mammogram spot film, courtesy of Dr. Mark R. Wick

Gross description
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• Firm, homogenous, gray-white-yellow, usually 3 cm or less and ill-defined

Gross images
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Firm tumor with irregular borders

Circumscribed pinkish-white mass

 

Courtesy of Dr. Mark R. Wick

Dense homogenous tumor
with infiltrating margins

Micro description
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• Infiltrating sheets/cords of polygonal bland cells with well-defined cell borders and abundant eosinophilic granular cytoplasm
• Round/oval nuclei with prominent nucleoli
• Collagenous stroma
• May be close to small nerve bundles and have infiltrative margins; occasional multinucleation
• Overlying epithelium may show pseudoepitheliomatous hyperplasia
• Rare mitotic figures, no/mild atypia

Micro images
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Core biopsy

Clusters of tumor cells

     

Abundant eosinophilic, granular cytoplasm

   

Courtesy of Dr. Mark R. Wick

Infiltration into fat

PAS+

     

Beneath squamous epithelium (not necessarily breast): H&E and S100

Mild nuclear pleomorphism

Malignant tumor (lung)

 

With DCIS and invasive ductal carcinoma

S100+

 

S100+ tumor cells and myoepithelial cells

S100, courtesy of Dr. Mark R. Wick

       

       

Contributed by Dr. Oleksandr Grygoruk, Boris Hospital and Medical Center, Kiev (Ukraine)

Cytology description
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• Highly cellular, large cohesive groups and single cells mixed with connective tissue
• Cells have ill defined, abundant granular cytoplasm and bland small nuclei with inconspicuous nucleoli
• No mitotic figures, no necrosis (Diagn Cytopathol 2007;35:725)

Cytology images
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FNAB, courtesy of Dr. Mark R. Wick

Positive stains
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• PAS (diastase resistant), S100, CD68 (due to phagolysosomes)
• Focal CEA and vimentin

Negative stains
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• Keratin, EMA, mucin
• Alpha-1-antitrypsin, myoglobin, ER, PR (Arch Pathol Lab Med 1984;108:897)

Electron microscopy descriptions
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• Myelin figures, lysosomes

Differential diagnosis
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• Alveolar soft part sarcoma: cells are divided into packets by thin walled vessels
• Apocrine carcinoma: usually ductal carcinoma also present, keratin+, mucin+, S100-
• Granulomatous inflammation
• Histiocytic tumors
• Melanoma
• Myoblastomatoid (histiocytoid) invasive carcinoma: keratin+
• Renal cell carcinoma

Additional references
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• eMedicine - Granular Cell Tumors

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