Immunohistochemical expression of PAX8, PAX2, and cytokeratin in melanomas

PAX5 and CD70 are expressed in thymic carcinoma but not in atypical thymoma (WHO type B3 thymoma): an immunohistochemical analysis of 60 cases

AIMS

Thymic carcinoma and atypical thymoma (WHO type B3 thymoma) are unusual tumours the separation of which may be challenging in small biopsies. Both tumours consist of epithelioid tumour cells that share similar morphology and immunophenotype with conventional markers. Therefore, additional antibodies are needed to differentiate between these tumours.

METHODS

For this purpose, a panel of immunohistochemical stains including PAX2, PAX5, PAX8 (all monoclonal) and CD70 was used on whole tumour sections of 30 thymic carcinomas and 30 atypical thymomas to determine the expression pattern of these antibodies. In addition, all tumours were stained with markers that are well known to be expressed in both tumours, including pancytokeratin and cytokeratin 5/6. The percentage of positive tumour cells as well as the intensity of staining were evaluated and scored.

RESULTS

PAX5 stained close to 70% of thymic carcinomas while all atypical thymomas were negative for this marker. CD70 was expressed in 18 thymic carcinomas (60%) and in 1 case of atypical thymoma (3%). On the other hand, monoclonal PAX8 was negative in all cases while PAX2 was positive in a single thymic carcinoma. Of the established stains, pancytokeratin and cytokeratin 5/6 were equally positive in both tumours.

CONCLUSIONS

Among the markers explored, only PAX5 and CD70 appear to be differentially expressed and are predominantly restricted to thymic carcinomas. Therefore, in small biopsy specimens and in resections in which the morphological features remain equivocal, application of these particular stains may facilitate separation of thymic carcinoma and atypical thymoma.

Combined tumour of aberrant cytokeratin expressing acral lentiginous melanoma and poroma: Diagnostic challenge

Combined tumours are uncommon and therefore these tumours may pose a diagnostic challenge. In the current case report, it is aimed to present the clinicopathological features of a combined tumour including melanoma with aberrant cytokeratin expression and poroma.

Metastatic melanoma and rare melanoma variants: a review

The histopathological diagnosis of melanoma is fraught with potential pitfalls. In the setting of cutaneous metastatic melanoma, it is important to recognise the various histological patterns that can be encountered from the more common to the rare, including epidermotropic, folliculotropic, naevoid, and blue naevus-like. In addition, melanoma is notorious for phenotypic plasticity. Thus, there are many different subtypes and cytomorphological variations that can be difficult to recognise as melanoma, particularly in the recurrent or metastatic setting. Select melanoma variants including primary dermal, clear cell, plasmacytoid, signet ring cell, small cell, myxoid, rhabdoid, and dedifferentiated melanoma will be discussed, in addition to composite melanocytic neoplasms. This review is intended to remind the practitioner of key concepts of metastatic disease and select rare melanoma variants, while providing practical guidelines for accurate diagnosis.

PAX2, PAX8, and PR are correlated with ovarian seromucinous borderline tumor with endometriosis

BACKGROUND

Ovarian "seromucinous carcinoma" has been recently removed in 2020 5^th Edition of WHO classification of Female Genital Tumors and is considered as a subtype of endometrioid carcinoma with mucinous differentiation, while "seromucinous borderline tumor" remains and exists as a distinct entity. Both diseases may be considered as no more same lineage. However, ovarian seromucinous borderline tumor (SMBT) is also one of the endometriosis-related neoplasm of ovary similar to endometrioid tumor, featuring that about 50% of ovarian SMBTs combine endometriosis. The present study was aimed to investigate whether the ovarian SMBTs are different in clinical features and molecular patterns, according to the presence of combined endometriosis.

RESULTS

There were no statistical differences in clinical findings between two groups. There was also no significant difference in pregnancy outcomes and recurrence between two groups. In immunohistochemical patterns, there was a statistically significant difference in PAX2 and PAX8 expression between in ovarian SMBT with or without endometriosis (P = 0.016, P < 0.001). Only a few cases of ovarian SMBT with endometriosis showed expression of PAX2 and conversely, most of the cases showed expression of PAX8. PR positivity was more prominent in ovarian SMBT with endometriosis than without endometriosis (P = 0.018), although there was no difference in positive ER expression. There were no statistical differences in WT1, CK20 and CDX2 expressions between two groups.

CONCLUSIONS

Ovarian SMBT with endometriosis did not clinically differ from that without endometriosis. However, the molecular patterns were different between two groups and ovarian SMBT with endometriosis is close to endometrioid tumor types unlike SMBT without endometriosis. Further, a direct comparison study between seromucinous borderline tumor and endometrioid borderline tumor is needed with a gene profiling study to prove their relationship.

Aberrant Expression of Immunohistochemical Markers in Malignant Melanoma: A Review

Immunohistochemical stains are increasingly used to aid in the diagnosis of malignant melanoma, especially when the differentiation of the tumor is unclear based on examination with hematoxylin and eosin. However, aberrant expression of non-melanocytic markers has been reported in melanomas, which can sometimes be further complicated by the loss of conventional melanocytic markers. This review aims to summarize available data regarding unusual staining patterns in primary and metastatic malignant melanoma. It also raises awareness of the potential pitfalls and highlights the importance of appropriate use and interpretation of broad immunohistochemical markers in the context of clinical and histopathologic findings to facilitate the diagnosis of atypical cases of malignant melanoma.