Intraoperative Frozen Cytology of Central Nervous System Neoplasms: An Ancillary Tool for Frozen Diagnosis

Abstract

BackgroundPathologic diagnosis of central nervous system (CNS) neoplasms is made by comparing light microscopic, immunohistochemical, and molecular cytogenetic findings with clinicoradiologic observations. Intraoperative frozen cytology smears can improve the diagnostic accuracy for CNS neoplasms. Here, we evaluate the diagnostic value of cytology in frozen diagnoses of CNS neoplasms.MethodsCases were selected from patients undergoing both frozen cytology and frozen sections. Diagnostic accuracy was evaluated.ResultsFour hundred and fifty-four cases were included in this retrospective single-center review study covering a span of 10 years. Five discrepant cases (1.1%) were found after excluding 53 deferred cases (31 cases of tentative diagnosis, 22 cases of inadequate frozen sampling). A total of 346 cases of complete concordance and 50 cases of partial concordance were classified as not discordant cases in the present study. Diagnostic accuracy of intraoperative frozen diagnosis was 87.2%, and the accuracy was 98.8% after excluding deferred cases. Discrepancies between frozen and permanent diagnoses (n = 5, 1.1%) were found in cases of nonrepresentative sampling (n = 2) and misinterpretation (n = 3). High concordance was observed more frequently in meningeal tumors (97/98, 99%), metastatic brain tumors (51/52, 98.1%), pituitary adenomas (86/89, 96.6%), schwannomas (45/47, 95.8%), high-grade astrocytic tumors (47/58, 81%), low grade astrocytic tumors (10/13, 76.9%), non-neoplastic lesions (23/36, 63.9%), in decreasing frequency.ConclusionsUsing intraoperative cytology and frozen sections of CNS tumors is a highly accurate diagnostic ancillary method, providing subtyping of CNS neoplasms, especially in frequently encountered entities.

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

“…We speculate that cytotechnologists treat tissue samples obtained from malignant lymphomas very carefully in squash preparations because they are very soft, applying as little pressure as possible in spreading the tissue into a thin film. In fact, there are no reports of severe crush artefacts related to the squash preparation process in cases of malignant central nervous system lymphoma . It also seems that the presence of lymphoglandular bodies in squash preparations of malignant lymphoma and of cytoplasmic fibrillary processes in squash preparations of glioma are characteristic cytological findings, although not necessarily always present, and that these features are useful in differentiating these tumours from other types of brain tumour.…”

“…In fact, there are no reports of severe crush artefacts related to the squash preparation process in cases of malignant central nervous system lymphoma. [2][3][4]11,12,16,17 It also seems that the presence of lymphoglandular bodies in squash preparations of malignant lymphoma and of cytoplasmic fibrillary processes in squash preparations of glioma are characteristic cytological findings, although not necessarily always present, and that these features are useful in differentiating these tumours from other types of brain tumour.…”

“…The difficulties lie mainly in evaluating tiny biopsy samples histomorphologically, and the soft, friable, watery nature of frozen brain tissue sections induces ice crystals throughout the tissue that can form artefactual spaces, even nuclear vacuoles. The high water content also causes sections to shatter easily . Pathologists can often discern only whether the biopsy specimen contains tumourous tissue, while the origin of the tumour and tumour cell differentiation status remains unclear.…”

“…Recent studies have indicated that squash cytology is more reliable than frozen section for intraoperative diagnoses of brain tumours, with reports of 76%‐95% accuracy . The procedure facilitates assessment of cell morphology, nuclear morphology and the nuclear chromatin pattern, with the resulting intraoperative report, of for instance the presence or absence of a lymphoid neoplasm or germ cell tumour, relaying a very practical message to the neurosurgeon.…”

“…3,10,11 Recent studies have indicated that squash cytology is more reliable than frozen section for intraoperative diagnoses of brain tumours, with reports of 76%-95% accuracy. [1][2][3][10][11][12][13] The procedure facilitates assessment of cell morphology, nuclear morphology and the nuclear chromatin pattern, with the resulting intraoperative report, of for instance the presence or absence of a lymphoid neoplasm or germ cell tumour, relaying a very practical message to the neurosurgeon. To investigate this promise further, we retrospectively assessed whether intraoperative cytological evaluation of squash preparations provided a useful qualitative diagnosis in cases for which frozen section yielded an intraoperative diagnosis of equivocal brain tumour.…”