PAX2 and PAX8: Useful Markers for Metastatic Effusions

Abstract

Objective: It was the aim of this study to determine the utility of PAX2 and PAX8 in cytology effusions with metastatic tumor. Study Design: PAX2 and PAX8 immunohistochemical staining was performed on cell blocks of 89 pleural, pericardial and peritoneal effusions with benign diagnoses (18 cases), or secondary to renal cell carcinoma (RCC; 9 cases), müllerian carcinoma (21 cases) or non-müllerian carcinoma (41 cases). Results: PAX2 stained 0% (0/18) of controls, 100% (8/8) of RCCs, 35% (7/20) of müllerian carcinomas, and 2% (1/41) of non-müllerian carcinomas. PAX8 stained 6% (1/18) of control cases, 100% (9/9) of RCC cases, 100% (20/20) of müllerian carcinomas, and 5% (2/41) of non-müllerian carcinomas. PAX2 was 35% sensitive and 95% specific for müllerian carcinoma and 100% sensitive and 95% specific for RCC. PAX8 was 100% sensitive and 95% specific for müllerian carcinoma and 100% sensitive and 95% specific for RCC. Conclusions: PAX8 is more sensitive than PAX2 for metastatic effusions from müllerian carcinomas (100 vs. 35%), while also having a higher intensity of staining than PAX2. However, PAX2 and PAX8 are both highly sensitive and specific for RCCs. PAX2 and PAX8 are valuable diagnostic markers for metastatic müllerian carcinomas and RCCs in effusion cytology. PAX8 is superior for carcinomas of müllerian origin.

Cytomorphology of ovarian clear cell carcinomas in peritoneal effusions

“…However, the corresponding peritoneal effusions are bloody in up to 1.2–2% of cases . Again the use of immunocytochemistry may be very useful as malignant cells from renal clear cell carcinoma are detectable using antibodies raised against CD10 and PAX2 and PAX8, the latter being also expressed in gynaecological neoplasms.…”

Utility of GATA‐3 in the work‐Up of breast adenocarcinoma and its differential diagnosis in serous effusions:

“…One should also be specifically aware that mesotheliomas may express GATA‐3 in 58% of cases. Therefore we propose using GATA‐3 in the right morphological setting and in a panel that includes other immunohistochemical markers helpful in excluding other primaries such as PAX‐8 helpful in excluding Müllerian origin, Calretinin to exclude mesothelioma, p63, p40 and CK5/6 to exclude squamous cell and urothelial carcinomas and TTF‐1 and Napsin to exclude pulmonary adenocarcinomas . Exceptional care should be given to the differential diagnosis of urothelial carcinoma and mesothelioma as GATA‐3 can be positive in both.…”

Clinically occult primary fallopian tube carcinoma presenting as a malignant pleural effusion

“…A wide array of immunohistochemical markers is available, although well‐established ones such as WT‐1, ER, PR and CA‐125 are limited by variable sensitivities and specificities and cannot always distinguish among the more common causes of metastatic malignancies in women, such as breast and ovarian carcinoma. PAX8 is a transcription factor of the paired box gene (PAX) family that serves as an important developmental regulator for the female genital tract . It has been recently demonstrated to be useful in distinguishing Müllerian from non‐Müllerian carcinomas in surgical specimens, fine needle aspirates and effusion specimens .…”