Intraoperative squash cytology provides a qualitative intraoperative diagnosis for cases in which frozen section yields a diagnosis of equivocal brain tumour

Cytologic features of mesenchymal, melanocytic and haematolymphoid tumours of the central nervous system and metastases

The current World Health Organization (WHO) classification of central nervous system (CNS) tumours includes several neoplasms that, while occurring in this location, are more frequently seen extracranially. These include mesenchymal, melanocytic and haematolymphoid neoplasms, as well as metastases. A few of these entities are exclusive of the CNS and have no extracranial counterpart. Despite their diverse histogenesis, these neoplasms share a peculiar predilection for involving meningeal structures. In fact, in the context of an intraoperative pathologic consultation of a meningeal tumour, virtually all these entities should be considered as potential diagnoses. Metastases in the CNS are very common. Most are carcinomas that cytologically resemble their site of origin. Loss of differentiation with cell dissociation and anaplasia and presence of accompanying fibrillary brain parenchyma can be a source of diagnostic problems. In this review, we intend to show the most relevant cytologic features of these tumours, and it is especially aimed at their analysis during intraoperative studies.

Touch imprint cytology is useful for the intraoperative pathological diagnosis of PitNETs' surgical margins

Touch imprint cytology (TIC) and frozen section (FS) procedures are essential for intraoperative pathological diagnosis (IPD). They are invaluable tools for therapeutic decision-making, helping surgeons avoid under or overtreatment of patients. Pituitary neuroendocrine tumors (PitNETs) are generally small, slow-growing tumors with low-grade malignancy located at the base of the skull where it is impossible to maintain a wide tumor margin. Therefore, transsphenoidal surgery (TSS) should be performed with necessary caution, and with sufficient and minimal resection. Thus, this study aimed to evaluate the diagnostic accuracy of TIC for the diagnosis of PitNET and determine its ability to accurately evaluate the surgical margin compared to the FS procedure. A total of 104 fresh specimens from 28 patients who underwent TSS for PitNETs were examined using TIC and FS. TIC specimens were categorized according to the cell imprinting pattern. All specimens with a large number of neuroendocrine cells diffusely attached to the glass surfaces had PitNET components. Contrarily, no rich or diffuse cell attachments were observed in any non-tumoral endocrine cells. In conclusion, recognizing a pattern of endocrine cell adherence to glass is highly effective in IPD to certify the existence of a PitNET component.

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.