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Presented by William Westra, M.D. and prepared by Natasha Rekhtman, M.D., Ph.D.
Case 2: 49 year-old woman with a sinonasal mass.
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1. Question
Week 206: Case 2
49 year-old woman with a sinonasal mass/images/12 6 04 case 2 1.JPG
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/images/12 6 04 case 2 4.JPGCorrect
Answer: Cellular schwannoma
Histology: The specimen consists of fragments of respiratory mucosa. The subepithelial tissues are diffusely infiltrated by a proliferation of spindle cells. The spindle cells demonstrate a fascicular growth pattern that, in some areas, shows a “herring bone” arrangement. The spindle cell proliferation is non-encapsulated and infiltrative with invasion of bone. The cells have uniform nuclei without significant atypia. Mitotic figures are not readily identified. The spindle cells are diffusely and strongly immunoreactive for S100.
Discussion: Schwannomas of the sinonasal tract can be treacherous neoplasms from a diagnostic perspective. They are sometimes hypercellular (lacking Antoni B areas), unencapsulated and locally destructive. Based on these features, they are easily mistaken as a malignant sarcoma. To avoid this diagnostic pitfall, pathologists must be aware of the quirkiness of schwannomas involving the sinonasal tract, and they must rely on immunohistochemistry when the differential diagnosis is not readily resolved on microscopic grounds alone. Like their counterpart in non-head and neck sites, cellular schwannomas of the sinonasal tract are immunoreactive for S100. Importantly, S100 positivity is strong and diffuse, unlike the focal patchy S100 positivity characteristic of most malignant nerve sheath tumors.
Following complete surgical excision, sinonasal schwannomas do not locally recur or metastasize. Therefore, lack of encapsulation and locally destructive growth in an otherwise histologically typical schwannoma arising at this site should not suggest malignant potential.
Incorrect
Answer: Cellular schwannoma
Histology: The specimen consists of fragments of respiratory mucosa. The subepithelial tissues are diffusely infiltrated by a proliferation of spindle cells. The spindle cells demonstrate a fascicular growth pattern that, in some areas, shows a “herring bone” arrangement. The spindle cell proliferation is non-encapsulated and infiltrative with invasion of bone. The cells have uniform nuclei without significant atypia. Mitotic figures are not readily identified. The spindle cells are diffusely and strongly immunoreactive for S100.
Discussion: Schwannomas of the sinonasal tract can be treacherous neoplasms from a diagnostic perspective. They are sometimes hypercellular (lacking Antoni B areas), unencapsulated and locally destructive. Based on these features, they are easily mistaken as a malignant sarcoma. To avoid this diagnostic pitfall, pathologists must be aware of the quirkiness of schwannomas involving the sinonasal tract, and they must rely on immunohistochemistry when the differential diagnosis is not readily resolved on microscopic grounds alone. Like their counterpart in non-head and neck sites, cellular schwannomas of the sinonasal tract are immunoreactive for S100. Importantly, S100 positivity is strong and diffuse, unlike the focal patchy S100 positivity characteristic of most malignant nerve sheath tumors.
Following complete surgical excision, sinonasal schwannomas do not locally recur or metastasize. Therefore, lack of encapsulation and locally destructive growth in an otherwise histologically typical schwannoma arising at this site should not suggest malignant potential.
