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

Fine needle aspiration of spindle cell lipoma-Lochkern cells as a clue for diagnosis: A case arising in the parotid gland

Spindle cell lipoma (SCL) is a rare form of lipoma, typically occurring as a mass in the back, shoulder or posterior neck of adult males. Most cases present little diagnostic difficulty on fine needle aspiration (FNA), but can be problematic when the SCL is in an unusual location. The authors report a case in the parotid gland in a 75-year-old man. FNA was paucicellular and showed loose collections of spindle cells with mild to moderate atypia, admixed with ropy collagen fibers on a myxoid background. The nuclei showed occasional angulation, interpreted on FNA as suspicious for myoepithelial tumor or low-grade sarcoma. The subsequent excisional specimen was diagnosed as SCL. On retrospective review of the FNA, an additional finding was recognized: 'naked' nuclei with intranuclear lipid vacuoles and positive immunostaining for S100 protein, consistent with Lochkern cells of mature adipocytes. This case highlights the challenges of diagnosing SCL on cytology when no fat-containing cells are apparent on the smear, and stresses the significance of Lochkern cells as a clue for diagnosis.

Cytological features of cranial and paraspinal nerve Tumours

The 2021 World Health Organization Classification of Central Nervous System Tumours introduced significant revisions to the categorization of paraspinal and nerve sheath tumours. This updated system encompasses seven tumour types: schwannoma, neurofibroma, perineurioma, hybrid nerve sheath tumours, malignant melanotic nerve sheath tumour, malignant peripheral nerve sheath tumour and cauda equina neuroendocrine tumour. This review provides an image-rich cytologic reference of these tumours, with particular emphasis on intraoperative smear preparations. Knowledge of the key cytological features of these tumours and their differential diagnoses will help guide classification of these challenging entities.

Cytopathology of mesenchymal tumors of the thyroid gland: analysis of 12 cases from multinational institutions with review of the literature

INTRODUCTION

Mesenchymal tumors of the thyroid gland are extremely rare. We report the cytomorphologic characteristics of 12 mesenchymal tumors occurring in the thyroid gland and highlight the diagnostic difficulties encountered in their cytologic evaluation.

MATERIALS AND METHODS

The cytopathology and surgical pathology archives from 5 large institutions were searched for thyroid mesenchymal tumors that had an FNA available for review. Clinicopathologic and cytomorphologic characteristics for each case were evaluated.

RESULTS

Twelve cases of mesenchymal tumors occurring in the thyroid were identified in our search. Patient age ranged from 28 to 84 years (median, 60 years). The cases occurred in 7 women and 5 men. The tumor size ranged from 1.4 to 14 cm (median, 3.3 cm). The tumors were as follows: hemangioma (n = 4; 33.3%), angiosarcoma (n = 2; 16.7%), schwannoma (n = 2; 16.7%), solitary fibrous tumor (n = 2, 16.7%), metastatic synovial sarcoma (n = 1, 8.3%) and metastatic pleomorphic rhabdomyosarcoma (n = 1, 8.3%). The cytomorphologic features of the tumors were similar to those of their counterparts occurring in different sites. An accurate diagnosis was achieved in six primary thyroid mesenchymal cases (60%). Five patients (41.7%) underwent total thyroidectomy, and 3 patients received partial thyroidectomy (25%). Three patients (25%) did not receive a thyroidectomy and subsequent surgical information was not available in 1 case (8.3%).

CONCLUSIONS

Mesenchymal tumors of the thyroid are extremely uncommon. Cytologic diagnosis of these tumors is often challenging due to the morphologic overlap with diverse epithelial and non-epithelial thyroid lesions. Ancillary studies such as immunohistochemistry and molecular studies are essential for accurate diagnosis.

Can EUS-FNA cytology reliably classify gastric submucosal spindle cell tumors?

BACKGROUND

Cytological diagnosis using endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) for gastric submucosal spindle cell tumors, such as gastrointestinal stromal tumors (GISTs), leiomyomas, and schwannomas, is challenging because of their similar morphological characteristics.

OBJECTIVE AND MATERIALS

To clarify the cytological differential points, we reviewed the EUS-FNA cytology specimens of GISTs (37 cases), leiomyomas (11 cases), and schwannomas (4 cases).

METHOD

Twelve cytomorphological features were evaluated: lymphocytes, crushed nuclei, naked spindle nuclei, mast cell, length of the streaming arrangement, cellularity, nuclei at the cluster margin (nuclei located at the periphery of the cell cluster), peripheral feathering (loosely aggregated cells at the margin of a cell cluster tended to taper like feathers), metachromasia, wavy nuclei, fishhook-type nuclei, and anisonucleosis.

RESULTS

Among these features, lymphocytes, naked spindle nuclei, length of the streaming arrangement, cellularity, nuclei at the cluster margins, peripheral feathering, and anisonucleosis were statistically significant for differentiation. Based on these findings, we developed an algorithm for cytodiagnosis. The algorithm was taught to four cytologists, and the interobserver agreement and correct diagnosis rates were compared before and after education, which showed a significant improvement.

DISCUSSION

The histological types of gastric submucosal spindle cell tumors can be estimated using this algorithm for EUS-FNA cytology. Furthermore, this algorithm can be applied for cytological diagnosis at bedside during rapid on-site evaluation.

Scoring system for intraoperative diagnosis of intracranial schwannoma by squash cytology

OBJECTIVE

To assess the utility of a newly developed squash cytology (SC)-based scoring system for accurate intraoperative diagnosis of schwannoma.

METHODS

We first compared SC-based and frozen section (FS) diagnoses with final pathological diagnoses of schwannoma (16 cases), meningioma (39 cases) and low-grade astrocytoma (16 cases). Then, by logistic regression modeling, we identified features of SC preparations that were independently predictive of schwannoma. To develop a diagnostic scoring system, we assigned one point to each feature, and performed receiver operating characteristic analysis to determine the score cut-off value that was most discriminatory for differentiating schwannoma from the other tumour types. We then compared accuracy, sensitivity, and specificity of diagnosis before and after the application of the scoring system.

RESULTS

Overall diagnostic concordance rates for SC and FS were almost the same, at 73.2% (52/71) and 77.5% (55/71 cases), respectively. Of the 16 SC features entered into the analysis, the following nine were found to independently predict schwannoma, and were thus incorporated into the scoring system: smooth cluster margins, few or no isolated tumour cells, fibrillary stroma, spindle-shaped nuclei, parallel arrangement of stroma, parallel arrangement of nuclei, presence of anisonucleosis, absence of nucleoli, and hemosiderin deposition. A cut-off score of four items yielded the best sensitivity, specificity and predictive values for prediction of schwannoma. Use of the scoring system improved accuracy of intraoperative diagnosis from 80.3% to 94.4%, sensitivity from 56.2% to 93.8%, and specificity from 87.3% to 94.5%.

CONCLUSION

Our proposed SC-based scoring system will increase accuracy of intraoperative diagnosis of schwannoma vs non-schwannoma tumours.

Cytomorphological and immunocytochemical diagnosis of an oesophageal mass in a 62-year-old female with dysphagia

Oesophageal schwannoma is an extremely rare benign neoplasm. Cytological diagnosis of oesophageal schwannoma has been sporadically reported in the literature. Herein, we present a case of oesophageal schwannoma in an older woman that could be accurately diagnosed based on endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) cytology accompanied by cell block immunocytochemistry.

Neurogenic Tumors of the Mediastinum

Neurogenic tumors represent a broad ill-defined category of neoplasms that includes tumors of Schwann cell and/or neuroblastic derivation, as well as neoplasms that typically develop in the central nervous system, but rarely present in ectopic sites including the mediastinum. Neurogenic tumors may occur at many different anatomic sites, but the mediastinum represents a uniquely challenging site given the complex anatomy. Additionally, some of these neoplasms may present with multicentric involvement in the context of genetic syndromes, including NF1, NF2 and schwanomatosis. Most of these develop in posterior structures, often in association with paraspinal structures. Fine needle biopsy/small biopsies play an important role in the diagnosis of these neoplasms, given its record of safety and the increased applicability of ancillary testing to these smaller samples at the present time. In this review we focus on the major categories of neurogenic tumors that may be encountered in the mediastinum, including schwannoma, neurofibroma, malignant peripheral nerve sheath tumors, ganglioneuroma and ganglioneuroblastoma, as well as rarer members of this category. We discuss diagnostic approaches applicable to small cytologic and tissue samples and relevant differential diagnoses.

Neisseria meningitidis Induces Pathology-Associated Cellular and Molecular Changes in Trigeminal Schwann Cells

Neisseria meningitidis, a common cause of sepsis and bacterial meningitis, infects the meninges and central nervous system (CNS), primarily via paracellular traversal across the blood-brain barrier (BBB) or blood-cerebrospinal fluid barrier. N. meningitidis is often present asymptomatically in the nasopharynx, and the nerves extending between the nasal cavity and the brain constitute an alternative route by which the meningococci may reach the CNS. To date, the cellular mechanisms involved in nerve infection are not fully understood. Peripheral nerve glial cells are phagocytic and are capable of eliminating microorganisms, but some pathogens may be able to overcome this protection mechanism and instead infect the glia, causing cell death or pathology. Here, we show that N. meningitidis readily infects trigeminal Schwann cells (the glial cells of the trigeminal nerve) in vitro in both two-dimensional and three-dimensional cell cultures. Infection of trigeminal Schwann cells may be one mechanism by which N. meningitidis is able to invade the CNS. Infection of the cells led to multinucleation and the appearance of atypical nuclei, with the presence of horseshoe nuclei and the budding of nuclei increasing over time. Using sequential window acquisition of all theoretical mass spectra (SWATH-MS) proteomics followed by bioinformatics pathway analysis, we showed that N. meningitidis induced protein alterations in the glia that were associated with altered intercellular signaling, cell-cell interactions, and cellular movement. The analysis also suggested that the alterations in protein levels were consistent with changes occurring in cancer. Thus, infection of the trigeminal nerve by N. meningitidis may have ongoing adverse effects on the biology of Schwann cells, which may lead to pathology.

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

Schwannoma rarely occurs in the stomach. We present a case of gastric schwannoma, which was initially evaluated by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) biopsy and confirmed by surgical resection. The patient was a 57-years-old woman with history of dyspepsia, who was found to have a large submucosal mass in the stomach. EUS-FNA showed scant spindle cells with abundant lymphocytes. The spindle cells were immunoreactive with S100, while negative for CD117, desmin, and CD34. The lymphocytes were mixed B-cells and T-cells. Immunostaining, flow cytometry, and molecular testing showed no evidence of B-cell lymphoma. The diagnosis of gastric schwannoma was confirmed by histopathological evaluation of the resected tumor. Gastric schwannoma has unique features of mixed spindle cells and lymphocytes. The tumor should be differentiated from other gastric mesenchymal tumors, and lymphoproliferative disorder is a pitfall.

Cytohistological and immunohistochemical characteristics of spindle-shaped mesenchymal neoplasms occurring in the gastrointestinal tract

The purpose of the present review is to analyze the cytohistological and immunohistochemical characteristics of spindle-shaped mesenchymal gastrointestinal neoplams (MGNs), a group of unusual neoplastic conditions with different biological behavior. These tumors exhibit clinical pictures strictly related to the site of origin and dimensions, even if they appear generally with an intramural localization. This latter point may suggest an useful application of endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA), mainly followed by the cell-block procedure (CBP) in the differential diagnostic approach. First of all, we discuss the most common entity of MGNs represented by gastrointestinal stromal tumors (GISTs), analyzing the morphologic characteristics and stressing the strength of immunohistochemical algorithm for diagnostic purposes. Successively, we have reported the less common group of spindle-shaped MGNs comprehensive of those arising elsewhere the soft tissues, such as leiomyomas, leiomyosarcomas, schwannomas, inflammatory myofibroblastic tumor and intra-abdominal desmoid fibromatosis. Finally, very uncommon spindle-shaped MGNs, like clear cell, follicular dendritic cell, undifferentiated pleomorphic and radiation-induced sarcomas as well as spindle cell dedifferentiated liposarcomas, have been briefly mentioned.

Cytologic and Immunohistochemical Evaluation of Low-Grade Spindle Cell Lesions of the Gastrointestinal Tract

Spindle cell lesions of the gastrointestinal tract are relatively uncommon compared with the frequency of their epithelial counterparts. Although gastrointestinal stromal tumors and leiomyomas are the most commonly encountered spindle cell lesions in the stomach and esophagus, respectively, there are other less common diagnostic entities that should be considered for accurate diagnoses as well as appropriate patient treatment and clinical follow-up. Given the morphologic overlap of low-grade spindle cell lesions on cytologic preparations, ancillary studies play a key role in differentiating these lesions from one another.