Multicentre study on the consistency of PD-L1 immunohistochemistry as predictive test for immunotherapy in non-small cell lung cancer.

AIMS: Investigate the impact of interlaboratory- and interobserver variability of immunohistochemistry on the assessment of programmed death ligand 1 (PD-L1) in non-small cell lung cancer (NSCLC). METHODS: Two tissue microarrays (TMAs) were constructed from 50 (TMA-A) and 51 (TMA-B) resected NSCLC cases, and distributed among eight centres. Immunostaining for PD-L1 was performed using Agilent's 22C3 pharmDx Assay (pharmDx) and/or a 22C3 laboratory developed test (LDT). The interlaboratory variability of staining- and interobserver variability of scoring for PD-L1 were assessed in selected critical samples (samples at the cut-off of positivity) and non-critical samples. Also, PD-L1 epitope deterioration in time in stored unstained slides was analysed. Krippendorff's alpha values (0=maximal, 1=no variability) were calculated as measure for variability. RESULTS: For interlaboratory variability of immunostaining, the percentage of PD-L1 positive cases among centres ranged 40%-51% (1% cut-off) and 23%-30% (50% cut-off). Alpha values at 1% cut-off were 0.88 (pharmDx) and 0.87 (LDT) and at 50% cut-off 0.82 (pharmDx) and 0.95 (LDT). Interobserver variability of scoring resulted in PD-L1 positive cases ranging 29%-55% (1% cut-off) and 14%-30% (50% cut-off) among pathologists. Alpha values were at 1% cut-off 0.83 (TMA-A) and 0.66 (TMA-B), and at 50% cut-off 0.77 (TMA-A) and 0.78 (TMA-B). Interlaboratory variability of staining was higher (p<0.001) in critical samples than in non-critical samples at 50% cut-off. Furthermore, PD-L1 epitope deterioration in unstained slides was observed after 12 weeks. CONCLUSIONS: The results provide insight in factors contributing to variability of immunohistochemical assessment of PD-L1, and contribute to more reliable predictive testing for PD-L1.

Cytologic diagnosis of rhabdomyosarcoma in a child with a pleural effusion. A case report.

BACKGROUND: A pleural effusion in children is usually caused by infectious diseases; malignant effusion is very uncommon. In a case of a malignant effusion in a child, a pleura-based metastasis of a neoplasm with a typically high prevalence in childhood has to be considered. Examples are neuroblastoma, nephroblastoma, Wilms' tumor, hepatoblastoma, malignant germ cell tumor and rhabdomyosarcoma. CASE: A 4-year old boy presented with a unilateral pleural effusion. Cytologic examination of the effusion revealed malignant small round cells admixed with very large cells with atypical nuclei. In formalin-fixed cell blocks prepared for immunocytochemistry the cells expressed desmin and myf-4. The cytologic diagnosis was consistent with metastatic rhabdomyosarcoma. Subsequent computed tomography revealed a mass above the diaphragm, which was biopsied. Histologic examination of a needle biopsy specimen confirmed the diagnosis of rhabdomyosarcoma. Molecular examination revealed a PAX3-FKHR fusion transcript specific to the alveolar type of rhabdomyosarcoma. CONCLUSION: This case illustrates the usefulness of immunocytochemistry on cell block preparations in diagnosing difficult cases of effusion cytology.

Gain of chromosome 7, as detected by in situ hybridization, strongly correlates with shorter survival in astrocytoma grade 2.

The clinical course of astrocytoma grade 2 (A2) is highly variable and is not reflected by morphological characteristics. Earlier studies using small series of A2 cases suggest that in situ hybridization (ISH) with chromosome-specific DNA probes allows for frequent detection of aneusomy 1, trisomy 7, and monosomy 10. The role of trisomy 7 in astrocytoma carcinogenesis is disputed, however, because of its presence in non-neoplastic brain tissue, as detected by karyotyping. Our objective was to investigate whether there was a correlation between chromosomal aberrations and survival in a series of 47 cases of A2. All cases were evaluated for numerical aberrations of chromosomes 1, 7, and 10 by ISH. Chromosomal aberrations were detected in 68% of cases of A2. Trisomy/polysomy 7 was seen in 31 cases (66%), 22 of which (47%) had a high percentage of this numerical aberration. Only 11 of these 22 cases also showed aneusomy for 1 or 10. No cells or only a few cells with aberrations were detected in non-neoplastic control samples. Using Kaplan-Meier analysis, trisomy/polysomy 7 correlated significantly with shorter survival. Hence, as determined by ISH, trisomy/polysomy 7 is absent in non-neoplastic brain tissue and is frequently detected in A2, correlating with the malignant progression of the disease.