• A dermal or subcutaneous tumor with abundant granular cytoplasm and Schwannian differentiation
• Nonneural variant (primitive polypoid granular cell tumor) shows similar granular cytomorphology but does not have immunohistochemical evidence of Schwannian differentiation

• Also known as Abrikossoff's tumor and granular cell schwannoma (Arch Otolaryngol 1968;88:174)
• Originally described as granular cell myoblastoma, given its resemblance to skeletal muscle myocytes (Am J Pathol 1947;23:721)

• D23.9: other benign neoplasm of skin, unspecified

• Common sites are trunk, upper limbs and head / neck
• Also arise on feet, hands, anogenital region and breast

• Pathogenesis of conventional granular cell tumors is unknown
• A subset of nonneural granular cell tumors (S100-) harbor ALK gene fusions (Am J Surg Pathol 2018;42:1133)

• Harboring multiple tumors has been associated with Noonan syndrome (Eur J Pediatr Surg 2013;23:257) and LEOPARD syndrome (Clin Genet 2009;75:185)

• Slowly growing papule or nodule; rarely ulcerates (Adv Anat Pathol 1999;6:186)
• Rare cases can exhibit multiple lesions (Cutis 2002;69:343)

• 48 year old woman with upper back nodule (Indian J Dermatol 2015;60:322)
• 51 year old woman with left posterior chest wall mass and lymph node metastases (Am J Dermatopathol 2015;37:334)
• 53 year old woman with an enlarging left lower abdominal nodule (Am J Dermatopathol 2010;32:370)
• 54 year old patient with toe lesion (Dermatol Res Pract 2010;2010:184125)
• 69 year old woman with a rapidly enlarging firm neck mass (Am J Dermatopathol 2017;39:e50)

• Benign and malignant tumors are typically treated with wide local excision (J Surg Oncol 1980;13:301)
• MOHS micrographic surgery is an option in anatomic sites in which conservative re-excision is desired (Case Rep Oncol Med 2012;2012:453569)

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• Greyish-white to pale yellow
• Oftentimes not well circumscribed

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• Infiltrative or circumscribed architecture
• Can involve the subcutis
• Large polygonal cells with abundant eosinophilic granular cytoplasm and small, central nuclei
• Epidermis can show pseudocarcinomatous hyperplasia
• Lysosomal macro-inclusions (pustulo-ovoid bodies of Milian) are usually present (J Cutan Pathol 2007;34:405)
• Can exhibit accentuation around arrector pili muscles or peripheral nerves (J Clin Pathol 2014;67:19)
• Nonneural granular cell tumors (S100-) can exhibit nucleomegaly, pleomorphism and variable mitotic activity (Am J Surg Pathol 1991;15:48, Histopathology 2005;47:179)

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• PASD, Sudan Black B, S100 (except for nonneural granular cell tumors), SOX10, NSE
• Variable staining for vimentin, CD68, NKI-C3 (CD63), MITF, CD56
• A subset of nonneural granular cell tumors express ALK

• HMB45, MelanA, AE1 / AE3, EMA, desmin
• Nonneural granular cell tumor is negative for S100

• Membrane bound cytoplasmic granules containing lysosomes of varying sizes (J Cutan Pathol 1981;8:277, Oral Surg Oral Med Oral Pathol 1977;44:227, Ultrastruct Pathol 2018;42:304)
• Larger secondary lysosomes can be seen
• Some membrane bound granules contain aggregates of virus-like particles
• Some lesional cells contain long spacing collagens (Luse bodies)
• Variably abundant basal lamina material may be seen

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• A subset of nonneural granular cell tumors harbor ALK gene fusions (Am J Surg Pathol 2018;42:1133)

A 40 year old woman presents with a nodule on her trunk. The lesion is biopsied and shows a dermal based proliferation of cells with abundant eosinophilic granular cytoplasm. Which of the following statements is false?


1. The abundant granular cytoplasm is indicative of numerous membrane bound cytoplasmic granules containing aggregates of lysosomes.
2. An S100 or SOX10 stain is positive in most tumors and is reflective of Schwannian differentiation.
3. Perineural accentuation of cellularity is a feature of malignancy.
4. These tumors can display infiltrative architecture and can sometimes involve the subcutaneous fat.

C. Perineural accentuation of cellularity is a feature of malignancy.

This is false since lesional cells of granular cell tumors can show a proclivity for peripheral nerves and arrector pili muscles. No studies have demonstrated increased malignant potential of granular cell tumors that exhibit these features.

Which of the following statements about granular cell tumors is false?


1. A subset are negative for S100 and other neural markers and can have a polypoid appearance.
2. Atypical features include necrosis, increased mitotic activity and nuclear pleomorphism.
3. NF1 is commonly mutated in conventional granular cell tumors.
4. Tumors can mimic granular cell variants of leiomyosarcoma, atypical fibroxanthoma and dermatofibroma.

C. NF1 is commonly mutated in conventional granular cell tumors.

This statement is false since the pathogenesis of granular cell tumors with Schwannian derivation has not been elucidated to date. A subset of nonneural granular cell tumors that are negative for neural markers (S100 negative) harbor ALK gene fusions.

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