Cytomorphologic features that distinguish schwannoma from other low‐grade spindle cell lesions

Abstract

BACKGROUND: Fine-needle aspiration biopsy of spindled mesenchymal lesions, including schwannomas, are challenging because of overlapping cytomorphological features. The objective of the current study was to identify key diagnostic cytological criteria for the diagnosis of schwannoma and to distinguish it from its common mimics. METHODS: A total of 58 schwannomas were evaluated and compared with 98 benign and low-grade spindle cell lesions, including 17 gastrointestinal stromal tumors and 20 fibromatosis cases. Biopsy confirmation was available for all cases. The authors semiquantitatively evaluated cellularity, quality of stroma (fibrous and fibrillar), the presence of single cells with bipolar cytoplasmic processes, and marked nuclear pleomorphism (in the absence of other features of malignancy). Nuclear features evaluated included fishhook-type nuclei, intranuclear inclusions, chromatin pattern, and nucleoli. RESULTS: Schwannomas demonstrated cohesive tissue fragments with fibrillary and occasionally fibrous stroma. The presence of intranuclear inclusions and marked nuclear pleomorphism and the absence of single cells with bipolar cytoplasmic processes emerged as statistically significant differences between the schwannoma and the nonschwannoma groups. When 5 criteria were present (high numbers of clusters, few to no single cells, fibrillary stroma, nuclei with pointed tips, and anisonucleosis) the sensitivity, specificity, positive predictive value, and negative predictive value for the diagnosis of schwannoma were 22%, 97%, 81%, and 68%, respectively. CONCLUSIONS:Cohesive tissue fragments with fibrillary/fibrous stroma, intranuclear inclusions, marked nuclear pleomorphism, and the absence of spindled cells with bipolar cytoplasmic processes are strongly suggestive of schwannoma and assist in excluding potential mimics. Cancer (Cancer Cytopathol) 2015;123:171-9.

Metastatic leiomyosarcoma to the pancreas diagnosed on endoscopic ultrasound‐guided fine needle aspiration – A report of two cases with review of spindle cell lesions of pancreas

“…The classical cytological features of schwannoma include tissue fragments with fibrillary stroma, wavy nuclei, Verocay bodies and intranuclear cytoplasmic inclusions. However, Chebib et al found that these features are not entirely specific for schwannoma. Intranuclear cytoplasmic inclusions may be seen in neurofibroma and LMS.…”

“…GIST is described in retroperitoneal location, but few case reports suggest its origin in pancreas. Presence of few epithelioid cells admixed with spindle cells along with absence of significant nuclear pleomorphism should raise a suspicion of GIST on morphology. Benign or malignant nature of GIST is based on size of tumour and mitotic count.…”

Endoscopic ultrasound‐guided fine‐needle aspiration biopsy of gastric schwannoma: Cytomorphologic features and diagnostic pitfalls

“…7,[22][23][24][25] Gastric schwannoma is an uncommon mesenchymal tumor characterized by spindle cell proliferation, which should be differentiated from other spindle cell tumors such as GIST and leiomyoma. Although the tumor cells of schwannoma, GIST and leiomyoma may have subtle differences in their cytomorphologic features, [11][12][13] the distinction of these entities primarily rest on the results of immunophenotypical analysis. Using a panel of immunostains including CD117, SMA, desmin, S100, and CD34 is often sufficient for their differential diagnosis.…”

“…[5][6][7][8][9] Although the cytomorphologic features of schwannoma are well described, [10][11][12][13] there are only a few case reports of gastric schwannoma in the literature. [5][6][7][8][9] Although the cytomorphologic features of schwannoma are well described, [10][11][12][13] there are only a few case reports of gastric schwannoma in the literature.…”

“…Rather endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is the choice of diagnostic approach for mesenchymal tumors including gastric schwannoma. [5][6][7][8][9] Although the cytomorphologic features of schwannoma are well described, [10][11][12][13] there are only a few case reports of gastric schwannoma in the literature. 8,14 Here, we presented a case report of gastric schwannoma in which the cytomorphologic features and diagnostic pitfalls were described, and the diagnosis was confirmed by surgical resection of the tumor.…”