Does Strong and Diffuse PAX-8 Positivity Occur in Primary Lung Carcinoma? An Immunohistochemical Study of 418 Cases and Review of the Literature

Prognostic value of PAX8 in small cell lung cancer

Objectives

Small cell lung cancer (SCLC) shows poor prognosis since it metastasizes widely at early stage. Paired box gene (PAX) 8 is a transcriptional factor of PAX family, of which the expression in lung cancer is a controversial issue, and its prognostic value of PAX8 in SCLC is still unclear.

Materials and methods

Overall, 184 subjects who were pathologically diagnosed with SCLC were enrolled in the study. Immunohistochemical analysis of PAX8 and Ki-67 were performed. The correlations between PAX8 expression and clinical features or Ki-67 index were further analyzed. Subsequently, an analysis of the association between PAX8, stage, Ki-67 status, and overall survival (OS) were performed in 169 subjects with follow-up information.

Results

PAX8 was positive in 53.8% (99/184) SCLC specimens. The positive rate is significantly higher in extensive-stage specimens (61.0%) than in limited-stage specimens (45.24%). PAX8 expression is positively correlated with Ki-67 index (P = 0.001) while negatively correlated with OS (HR = 3.725, 95% CI 1.943-7.139, P＜0.001). In combination groups, the PAX8 negative and limited stage group had the most promising OS.

Conclusion

PAX8 expression rate in SCLC specimens is not low. It has prognostic value in small cell lung cancer.

An Unlikely Source of Iodine Uptake: A Bronchogenic Cyst Masquerading as Metastatic Thyroid Cancer

Radioactive iodine therapy and posttreatment scanning are essential components of differentiated thyroid carcinoma treatment and detection of metastatic disease. False-positive results can be seen on an I-131 scan and are important for clinicians to be aware of. Here, we present a case of a 33-year-old female with follicular thyroid carcinoma who was noted to have an area of moderate uptake in the chest on a whole-body scan following remnant ablation with 30 mCi of I-131 (1.11GBq) concerning for a metastatic hilar lymph node. This was determined to be a mediastinal bronchogenic cyst on surgical pathology. It has been previously proposed that the expression of sodium iodide symporters in some bronchogenic cysts could be the mechanism by which iodine uptake is seen within them. We were able to demonstrate positive immunohistochemical staining for both sodium iodide symporter and the associated paired box gene 8 transcription factor in the cyst sample, which supports the proposed theory.

Carcinoma of unknown primary (CUP): an update for histopathologists

Carcinoma of unknown primary (CUP) is a heterogeneous group of metastatic cancers in which the site of origin is not identifiable. These carcinomas have a poor outcome due to their late presentation with metastatic disease, difficulty in identifying the origin and delay in treatment. The aim of the pathologist is to broadly classify and subtype the cancer and, where possible, to confirm the likely primary site as this information best predicts patient outcome and guides treatment. In this review, we provide histopathologists with diagnostic practice points which contribute to identifying the primary origin in such cases. We present the current clinical evaluation and management from the point of view of the oncologist. We discuss the role of the pathologist in the diagnostic pathway including the control of pre-analytical conditions, assessment of sample adequacy, diagnosis of cancer including diagnostic pitfalls, and evaluation of prognostic and predictive markers. An integrated diagnostic report is ideal in cases of CUP, with results discussed at a forum such as a molecular tumour board and matched with targeted treatment. This highly specialized evolving area ultimately leads to personalized oncology and potentially improved outcomes for patients.

Napsin A Expression in Subtypes of Thyroid Tumors: Comparison with Lung Adenocarcinomas

Napsin A is widely used in the diagnosis of lung adenocarcinoma and has also been reported to be positive in cases of thyroid carcinomas. We investigated napsin A levels through immunohistochemistry on whole sections of 210 primary thyroid tumors of various subtypes and another 41 metastatic thyroid carcinomas, and compared these with 125 primary and 25 metastatic lung adenocarcinomas. The results showed that napsin A was expressed in 23.8% thyroid tumors and 30.3% papillary thyroid carcinomas. Most cases showed a focal and weak to moderate expression. In comparison, 80.8% primary lung adenocarcinomas expressed napsin A, with mostly diffused and strong expression. For metastatic carcinomas of thyroid and lung origin, napsin A was detected in 39.0% of thyroid carcinomas in contrast to 88.0% in cases of lung adenocarcinomas. Comparisons of additional markers, TTF-1, CK7, thyroglobulin, and Pax-8 in metastatic carcinomas showed the overlapping expression of immunomarkers of TTF-1 and CK7. Thyroglobulin and Pax-8 were useful for distinguishing between metastatic carcinomas; however, Pax-8 may be a superior marker due to its higher sensitivity. The clinicopathological analysis of papillary thyroid carcinomas showed that the expression of napsin A was positively correlated with lymph node metastasis (p = 0.030). Here, we focused on the expression of napsin A in thyroid tumors and compared it with that in lung adenocarcinomas. The expression of napsin A is common in thyroid tumors and the combined expression of napsin A and TTF-1 in a metastatic thyroid carcinoma is a cause for concern due to chances of misdiagnosis as lung adenocarcinoma.

Evaluation of Carcinoma of Unknown Primary on Cytologic Specimens

Carcinoma of unknown primary is defined as metastatic carcinoma without a clinically obvious primary tumor. Determining the tissue of origin in carcinoma of unknown primary is important for site-directed therapy. Immunohistochemistry is the most widely used tool for the work-up of metastases, but molecular profiling assays are also available. This review provides an overview of immunohistochemical stains in the work-up of metastatic carcinoma, with a focus on newer site-specific markers, and discusses the role of gene expression profiling assays for determining tissue of origin. The utility of cytopathology specimens in the evaluation of carcinoma of unknown primary also is highlighted.