Bone

Immunohistochemistry for histone H3G34W and H3K36M is highly specific for giant cell tumor of bone and chondroblastoma, respectively, in FNA and core needle biopsy

“…The utility of FNA and/or CNB in the evaluation of primary bone tumors currently is limited to a few large tertiary centers 10,21 due to a combination of the uneasiness of general cytopathologists with regard to primary bone tumors, a high insufficient rate in certain tumors, 6 mounting challenges in distinguishing highly malignant giant cell-rich osteosarcoma from locally aggressive giant cell-rich neoplasms such as GCT of bone and chondroblastoma, 7–10 and the lack of helpful diagnostic markers for these difficult differential diagnoses. Recent advances in understanding the underlying genetics in bone tumors, notably H3.3 mutations in GCT of bone and chondroblastoma, 11 have not only broadened our understanding of the pathogenesis of these bone tumors but also have provided us with novel diagnostic tools, thereby opening a new era of using FNA and/or CNB in the evaluation of primary bone tumors.…”

Cytology of Undifferentiated Round-Cell Sarcomas of Bone and Soft Tissue: Ewing Sarcoma or Not Ewing Sarcoma, That Is the Question

“…Small-cell osteosarcoma smears show a mixture of dispersed and cohesive clusters of mildly pleomorphic population of round- and spindle-shaped cells. Cytologic features may be very similar to ES or Ewing-like sarcomas, and finding osteoids may lead to correct diagnosis [66, 68]. SATB2 expression is a potential pitfall in differential diagnosis because this traditionally believed to be osteoblastic differentiation marker is also positive in BCOR - CCNB3 sarcoma [64].…”

Squash smear and fine needle aspiration features of conventional chordoma

“…8,9,13 The most characteristic and highly diagnostic types of cells in chordoma are physaliferous cells (Figure 4), but the definition of these cells is not well established. 12,13 Usually, they are described as large polygonal or epithelioid cells with large cytoplasmic vacuoles, but some authors use more strict criteria and for diagnosis require a high nuclear/ cytoplasmic ratio or a "spider cell" appearance, where cytoplasmic strands surround vacuoles and nuclei. 8,14,15 If Romanowsky-type stains are used, physaliferous cells usually appear poorly stained (Figure 5).…”

“…Cell borders are usually prominent in dispersed cells and can be absent within syncytial cell groups. 8,12,13 In less than half of the cases, intranuclear cytoplasmic pseudoinclusions can be observed (Figure 6). 8 In some cases atypical cytological features, like significant pleomorphism, hyperchromasia and mitotic activity, may be observed, but the significance of these findings is not yet well understood.…”

“…The other tumours that should be included in the differential diagnosis are chordoid meningioma, myxopapillary ependymoma and metastatic mucinous adenocarcinoma. 13 Due to the abundant extracellular matrix, chordoid meningioma should be included as a differential diagnosis. In both entities, cytoplasmic vacuolisation and intranuclear cytoplasmic pseudoinclusions can be also observed.…”