Ewing sarcoma (ES)/ primitive neuroectodermal tumour (PNET) is an aggressive malignant neoplasm affecting mainly children and young adults. The tumour is included with other primitive neoplasms under the category of small round cell tumour. Cytokeratin expression in ES/PNET has been described in sporadic case reports as well as a few systemic series. We studied this feature in Malaysian patients diagnosed in University Malaya Medical Centre on the basis of typical morphology and immunohistochemical assays. Immunohistochemical staining for AE1/AE3 and MNF116 were performed in 43 cases. Cytokeratin was expressed in 17 cases (39.5%) in focal, intermediate or diffuse patterns. There was no significant association between cytokeratin immunoreactivity and the following parameters: patient age, sex, skeletal and extraskeletal primary location as well as primary, metastastic or recurrent tumours or chemotherapy treatment. A significant association between cytokeratin and neuron specific enolase (NSE) expression was demonstrated. Our study supports evidence of epithelial differentiation in ES/PNET and emphasizes that the expression of cytokeratin does not exclude ES/PNET in the differential diagnosis of small round cell tumours.

Persistence and eventual integration of high-risk HPV (hrHPV) into the cervical cell is crucial to the progression of cervical neoplasia and it would be beneficial to morphologically identify this transformation in routine surgical pathology practice. Increased p16INK4a (p16) expression is a downstream event following HPV E7 binding to pRB. A study was conducted to assess the correlation between hrHPV detection using a commercial in-situ hybridization assay (Ventana INFORM HPV ISH) and p16 immunoexpression (CINtec Histology Kit) in cervical squamous intraepithelial lesions and squamous carcinoma. 27 formalin-fixed, paraffin-embedded cervical low-grade squamous intraepithelial lesions (LSIL), 21 high-grade squamous intraepithelial lesions (HSIL) and 51 squamous carcinoma (SCC) were interrogated. hrHPV was significantly more frequent in HSIL (76.2%) and SCC (88.2%) compared to LSIL(37.0%). p16 expression was similarly more frequent in HSIL (95.2%) and SCC (90.2%) compared to LSIL(3.7%). That the rates of hrHPV when compared with p16 expression were almost equivalent in HSIL and SCC while p16 was expressed in only 1 of the 10 LSIL with hrHPV, are expected considering the likelihood that transformation has occurred in HSIL and SCC but does not occur in majority of LSIL.