Usefulness of PAX8 Immunohistochemistry in Adult Intraocular Tumor Diagnosis

The Histological Spectrum of DICER1-Associated Neoplasms

DICER1 syndrome is a heterogeneous cancer predisposition syndrome, characterized by a large variety of benign and malignant tumor types, and caused by germline heterozygous pathogenic variants in the DICER1 gene, which is essential in miRNA processing and RNA interference. The clinical manifestations are diverse, with pleuropulmonary blastoma, Sertoli-Leydig cell tumor, cystic nephroma, uterine cervical embryonal rhabdomyosarcoma, and thyroid follicular nodular disease being the most prevalent tumor types. Since these neoplasms are rare and particularly occur in the pediatric population, pathologists should be aware of the potential relationship of these tumors with an underlying DICER1 syndrome in order to perform or suggest additional molecular pathologic analysis and refer patients and their parents for genetic counseling and testing. This review describes the various DICER1-related tumor types with emphasis on the histological features, reflects on the molecular pathogenesis of DICER1, and aims to raise awareness of this syndrome to facilitate earlier diagnosis.

PAX3 expression patterns in ocular surface melanocytes

PAX3, a transcription factor essential for neural crest development and melanocyte progenitors, is expressed in various melanocytic tissues. However, its role in ocular surface tissues remains poorly understood. This study investigated the expression patterns of PAX3 in the limbal stem cell niche, specifically in limbal epithelial progenitor cells (LEPC), limbal melanocytes (LM), and limbal mesenchymal stem cells (LMSC). Additionally, PAX3 expression was studied in conjunctival/limbal melanoma specimens. Immunohistochemical analysis revealed predominant PAX3 expression in LM as well in the conjunctival melanocytes, suggesting distinct roles in stem cell regulation and melanocyte maintenance. Notably, PAX3 was significantly upregulated in conjunctival/limbal melanoma tissues compared to healthy counterparts, with expression co-localizing with melanocyte markers (Melan-A, HMB45, SOX10) and the proliferation marker Ki-67 in melanoma cells. These findings suggests that while PAX3 expression is restricted to melanocytes in limbal/conjunctival tissues and its dysregulation may play a crucial role in conjunctival/limbal melanoma development. Further investigation into mechanisms by which PAX3 influences corneal pathophysiology and contributes to conjunctival/limbal melanoma pathogenesis could identify potential therapeutic targets for this aggressive ocular malignancy.

Consultations in Eye Pathology: Experience at an Ophthalmology Specialty Hospital

CONTEXT.—

Ophthalmic pathology is a discipline that relies heavily on a knowledge of clinical ophthalmology. The diagnosis of ocular and periocular lesions can be challenging because some lesions and diseases are unique to this region, whereas others may demonstrate site-specific differences from nonocular counterparts. Because of these challenges, ocular and periocular biopsies are frequently referred to specialized ophthalmic pathology centers for second-opinion diagnoses.

OBJECTIVE.—

To analyze the referral patterns, diagnostic challenges, and diagnostic discrepancies for second-opinion referrals at a dedicated ophthalmic pathology laboratory with an emphasis on lesions of special interest in ophthalmic pathology.

DATA SOURCES.—

Data sources included the pathology records of all slides and blocks received in consultation at the referral eye pathology center between December 1, 2015, and December 1, 2022, the personal experience of senior authors, and published peer-reviewed literature.

CONCLUSIONS.—

Corneal, intraocular, and conjunctival biopsies are the most common types of cases received in consultation without the referring pathologist's diagnosis, likely reflecting diagnostic challenges. Degenerative intraocular processes occasionally raise concern for a neoplasm. Conjunctival melanocytic lesions are the most common conjunctival biopsies referred for second-opinion diagnosis and require careful tissue sampling and clinical-pathologic correlation. Careful clinical-pathologic correlation, a high level of suspicion, and adequate sampling also are required for the accurate diagnosis of periocular sebaceous carcinoma. The diagnostic discrepancies involving uveal, retinal, conjunctival, eyelid, and temporal artery biopsies are most likely to adversely influence patient management and possible outcome. Such specimens may benefit from referral to specialized ophthalmic pathology laboratories.

Adenomas of the ciliary body epithelium: clinics, histopathology and management

AIMS

Adenomas of the ciliary body epithelium, including adenoma of the pigmented ciliary body epithelium (APCE) and adenoma of the non-pigmented ciliary body epithelium (ANPCE), are extremely rare, and most knowledge about them comes from sporadic case reports. The purpose of this study was to provide a comprehensive understanding of adenomas of the ciliary body epithelium and to identify the similarities and differences between APCE and ANPCE.

METHODS

This study was a retrospective case series comprising data from 41 patients obtained from retrieved publications and five cases diagnosed at the Shanghai Ninth People's Hospital. The clinicopathological features, treatment and prognosis of APCE and ANPCE were compared using the non-parametric rank sum test, t-test and the χ2 test.

RESULTS

The clinical and histopathological features and treatment were analogous between APCE (n=23) and ANPCE (n=23). The overall visual prognosis associated with the two tumours was good, with 63% of the patients having stable or improved vision after treatment. Enucleation was the primary cause of eventual vision loss (three in APCE vs two in ANPCE, p=0.001). Notably, iris invasion was commonly observed in patients with APCE (six in APCE vs zero in ANPCE, p=0.014), and iris invasion was associated with decreased vision eventually (p=0.003). Tumour size was irrelevant to the vision outcome (p=0.65). Metastasis or recurrence did not occur in any of the patients.

CONCLUSION

In most cases, the clinicopathological features of ANPCE and APCE were similar. Iris invasion was commonly observed in patients with APCE, which was associated with poor visual prognosis.

Pseudo second anterior lens capsule during post-vitrectomy cataract surgery: A case report

Purpose

To report the unexpected finding of a membrane resembling a second anterior lens capsule during cataract surgery after previous pars plana vitrectomy (PPV) with silicone oil tamponade for retinal detachment.

Observations

A 26-year-old male with a history of two retinal detachment repairs of the right eye over a 5-month period, presented with decreased vision. The first retinal detachment repair was performed with a 23-gauge PPV and the second with a 25-gauge PPV, scleral buckle and placement of silicone oil. Additional ocular history includes bilateral megalocornea, high myopia, and temporal lens coloboma. Upon presentation, slit lamp exam showed migration of silicone oil to the anterior chamber and a nuclear cataract. A decision was made to perform combined silicone oil removal and cataract extraction with intraocular lens (IOL) implant of the right eye. After capsulorrhexis, hydrodissection of the lens was not completed successfully since the presence of a membrane was detected. This membrane was cut, achieving partial completion of the second capsulorrhexis, which was further advanced using a forceps following the contour of the first capsulorrhexis. The cataract was removed without further difficulty and the IOL was placed into the capsular bag with good centration. The membrane was submitted to pathology, and upon microscopic examination was found to represent fibrocellular tissue with some cells expressing PAX8 and cytokeratin AE1/AE3.

Conclusions and importance

This case reports the unusual finding of a membrane that behaved as a second anterior lens capsule intraoperatively and that expressed novel pathology markers. These findings may better prepare ophthalmologists for similar pathologies they may encounter during capsulorrhexis.

Immunohistochemical expression of PAX8, PAX2, and cytokeratin in melanomas

BACKGROUND

Deviations from the classic melanocytic immunophenotype in melanoma can present a diagnostic challenge. PAX8 and PAX2 are common markers for renal or Müllerian differentiation. While most PAX8+ or PAX2+ carcinomas are seldom confused with melanoma, some cases may show a more ambiguous immunophenotype, especially when MiTF family altered renal cell carcinoma (MiTF-RCC) is in the differential diagnosis. Neither PAX8 nor PAX2 expression has been reported in melanoma to date. We aimed to better characterize PAX8, PAX2, and cytokeratin immunoreactivity in a large series of melanomas.

METHODS

Tissue microarrays consisting of 263 melanomas were immunostained for PAX8, PAX2, and cytokeratin and graded by an h-score.

RESULTS

PAX8 expression was seen in 7.9% of melanomas and was significantly associated with spindle cytomorphology. PAX2 was positive in one (0.4%) melanoma. Cytokeratin positivity was seen in three (1.2%) cases and was associated with metastases.

CONCLUSIONS

PAX8 is expressed in a subset of melanomas and may be strong/extensive. As PAX8 positivity does not exclude a diagnosis of melanoma, it should be used in conjunction with other immunohistochemical markers, such as cytokeratin and PAX2, when melanoma, MiTF-RCC, and other PAX8+ tumors are in the differential diagnosis.

Paired-Box Gene 8 (PAX8) and Its Association With Epithelial Carcinomas

Cancer is the second most common culprit of mortality in the United States and epithelial carcinomas are considered as one of the most predominant types of cancer. The association between epithelial cancers and paired-box gene 8 (PAX8) has been studied significantly before. PAX8 belongs to the paired-box gene family, which plays an important role in the organogenesis of different body organ systems, especially the thyroid gland, the renal system, and the Müllerian system. Immunohistochemical staining is being used to detect PAX8 expression in different epithelial cancers and differentiate them from PAX8-negative tumors. In follicular, papillary, and anaplastic thyroid carcinomas, targeting the PAX8/peroxisome proliferator-activated receptors (PPARs) fusion protein is being considered as a potential mechanism for therapy. Moreover, because of its high expression in primary ovarian cancers, PAX8 is being considered as a target for ovarian cancer treatment as well. More studies are needed to test the possibility of using PAX8 as a possible target for managing endometrial carcinomas. In this article, we review the functions of the PAX8 gene, how its mutations lead to the development of certain epithelial carcinomas, how it can be used as a diagnostic or a prognostic marker, and its potential as a therapeutic target for these cancers.

PAX8 Expression in the Crystalline Lens and Lens-Derived Lesions

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