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A 12-year-old adolescent was diagnosed with a right-sided solid mass in the round ligament of the uterus. The chief complaints were abdominal pain and pelvic discomfort. She underwent laparoscopic tumor resection. Histological examination demonstrated a trabecular growth pattern of epithelioid cells with mitotic activity (3 per 50 HPF), which expressed melanocytic and myoid markers. Due to aforementioned findings, a final diagnosis of perivascular epithelioid cell tumor (PEComa) with uncertain malignant potential was made. To the best of our knowledge, this localization of PEComa is considered to be infrequent with only occasionally reported cases. [ABSTRACT FROM AUTHOR]

A 12-year-old adolescent was diagnosed with a right-sided solid mass in the round ligament of the uterus. The chief complaints were abdominal pain and pelvic discomfort. She underwent laparoscopic tumor resection. Histological examination demonstrated a trabecular growth pattern of epithelioid cells with mitotic activity (3 per 50 HPF), which expressed melanocytic and myoid markers. Due to aforementioned findings, a final diagnosis of perivascular epithelioid cell tumor (PEComa) with uncertain malignant potential was made. To the best of our knowledge, this localization of PEComa is considered to be infrequent with only occasionally reported cases.

Background: Rhabdoid melanoma is a rare variant of malignant melanoma with characteristic cytomorphologic features. Due to the potential loss of conventional melanocytic markers, histopathologic diagnosis is often challenging. We hypothesize that immunostaining for PReferentially expressed Antigen in MElanoma (PRAME) might have the potential to uncover the melanocytic origin of these dedifferentiated tumors. Methods: Four cases of rhabdoid primary melanomas were assessed by immunohistochemistry for expression of PRAME and conventional melanocytic markers. Immunohistochemical expression patterns were analyzed in the rhabdoid primaries and, if available, associated metastases. Results: All four cases of rhabdoid primary melanomas showed a strong nuclear positivity for PRAME, while the expression of conventional melanocytic markers S100, MART-1, SOX-10 and HMB-45 was variable between the analyzed cases. Conclusions: In summary, we report four cases of rhabdoid primary melanoma with high to intermediate expression of PRAME despite the partial and variable loss of other melanocytic markers. Hence, PRAME might facilitate the recognition of this highly aggressive entity to avoid misdiagnosis due to histopathologic pitfalls.

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.

Background: Rhabdoid melanoma is a rare variant of malignant melanoma with characteristic cytomorphologic features. Due to the potential loss of conventional melanocytic markers, histopathologic diagnosis is often challenging. We hypothesize that immunostaining for PReferentially expressed Antigen in MElanoma (PRAME) might have the potential to uncover the melanocytic origin of these dedifferentiated tumors. Methods: Four cases of rhabdoid primary melanomas were assessed by immunohistochemistry for expression of PRAME and conventional melanocytic markers. Immunohistochemical expression patterns were analyzed in the rhabdoid primaries and, if available, associated metastases. Results: All four cases of rhabdoid primary melanomas showed a strong nuclear positivity for PRAME, while the expression of conventional melanocytic markers S100, MART-1, SOX-10 and HMB-45 was variable between the analyzed cases. Conclusions: In summary, we report four cases of rhabdoid primary melanoma with high to intermediate expression of PRAME despite the partial and variable loss of other melanocytic markers. Hence, PRAME might facilitate the recognition of this highly aggressive entity to avoid misdiagnosis due to histopathologic pitfalls. [ABSTRACT FROM AUTHOR]

The presence of melanin pigment and melanocytic markers expression have been rarely reported in salivary gland tumors. Herein, two cases of carcinoma arising in pleomorphic adenoma of the parotid gland and showing diffuse expression of myoepithelial and melanocytic markers are described. The clinical-pathological clues useful in the differential diagnosis with melanoma are discussed. In addition, a review of the pertinent literature is also proposed, discussing the pathologic mechanisms potentially involved in this phenomenon. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Perivascular epithelioid cell tumors (PEComa)s are mesenchymal neoplasms composed of perivascular epithelioid cells, which express both melanocytic and myogenic markers. These neoplastic cells are thought to arise from undifferentiated cells of the neural crest, or from myoblastic cells harbouring a molecular alteration leading to expression of melanocytic markers, or from pericytic cells. The majority of cases are benign, but a small subset behaves in a malignant fashion. Unfortunately, given their rarity, reliable criteria for predicting malignancy have yet to be established. PEComas of the female genital tract account for nearly 25% of PEComas of all body sites, and the most common site of occurrence is the uterine corpus; less common sites include the cervix, adnexa, vagina/vulva or broad or round ligament exceptionally. The present review aims to elucidate the clinical, pathological and molecular features of gynecological PEComas. Moreover, prognostic and therapeutic implications are also discussed.

Pigmentation of the skin is a crucial component in the pathogenesis of melanocytic neoplasms and other skin-related tumors, as melanin is known to function in both the absorbance of ultraviolet radiation and as an antioxidant. Very limited information exists regarding the incidence and metastatic potential of neoplastic conditions of the skin in game animals, especially wildebeests, relative to domestic animals. Four cases of cutaneous melanoma in color-variant golden and king wildebeests ( Connochaetes taurinus) (from 2014 to 2015) in South Africa were investigated. Melanoma in these captive animals was characterized using histopathology, transmission electron microscopy, and an immunohistochemistry panel, which consisted of monoclonal antibodies against three melanocytic markers: Melan A, PNL2, and S100. Overall, 2/4 cases (50%) of the melanocytic neoplasms stained strongly positive for all the melanocytic markers, while 4/4 cases (100%) stained positively for at least one of the markers. Cutaneous melanocytic neoplasia has not been reported in wildebeests; the current study suggests that selection of wildebeests for coat color potentially predisposes to this condition. [ABSTRACT FROM AUTHOR]

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A comparative immunohistochemical study was performed on Paget's disease of the nipple (PDN), extramammary Paget's disease (EMPD) and cutaneous superficial spreading melanoma (SSM) using antibodies to S100, NK1-C3 and HMB45, cytokeratin (CAM 5.2) and c-erb B2 oncoprotein (21N). Conventional histochemical stains for intracytoplasmic mucin and melanin were also done. Of the 20 cases of PDN, positivity was seen in 12 with S100, 16 with NK1-C3, none with HMB45, 20 with CAM 5.2 and 19 with 21N. All 5 cases of EMPD were CAM 5.2 positive and HMB45, S100 and 21N negative. Three EMPD were NK1-C3 positive. All 10 cases of SSM were S100, NK1-C3 and HMB45 positive and all were CAM5.2 and 21N negative. Mucin was demonstrable in 11 cases of PDN and all of EMPD but none of SSM. Melanin was seen in 2 PDN, 3 EMPD and all SSM cases. Identification of mucin and melanin, therefore, proved an unreliable means of distinguishing these diseases. Immunohistochemistry for cytokeratin and HMB45 appear to be the most specific markers in differentiating Paget's disease and SSM. Antibodies to c-erb B2 may also be valuable in this situation. [ABSTRACT FROM AUTHOR]

Background: Perivascular epithelioid cell tumors (PEComa)s are mesenchymal neoplasms located at various anatomic sites, which usually express both melanocytic and myogenic markers., Case Report: A 60-year-old woman underwent laparotomy for a huge, heterogeneous, right ovarian mass. The histological examination of the surgical specimen revealed a neoplasm consisting of both cells with clear or eosinophilic cytoplasm and spindle cells in a myxoid stroma. Immunostaining was positive for human melanoma black-45, h-caldesmon, desmin, actin, and transcription factor 3. Cell atypias were moderate, mitoses were 4/10 high power fields (HPF) and margins were focally infiltrative. These findings pointed to a diagnosis of ovarian PEComa. Twenty-five months later, two subcutaneous lesions were surgically removed on the left trapezius muscle and the median subumbilical area, respectively. The former was a desmoid fibromatosis, whereas the latter was a recurrence of PEComa with greater nuclear pleomorphism and higher number of mitoses (26/50 HPF) compared to the primary tumor. The patient was free of disease 11 months later., Conclusion: A long-term follow-up of gynecological PEComas is strongly recommended., (Copyright © 2021 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

A 61-year-old man presented to the emergency room with significant weight loss. Laboratory analysis revealed elevations in blood urea nitrogen, creatinine, and white blood cell count. Computed tomography imaging showed a large, infiltrative mass in the right renal vein, with metastasis to the brain. Biopsy of soft tissue mass and kidney revealed positive staining for malignant melanoma. Malignant melanoma to the kidney is extremely rare, and imaging modalities alone cannot differentiate neoplasms in the kidney. It is therefore necessary to use specific immunocytochemical staining along with imaging modalities to make a specific diagnosis when the primary origin of the tumor is unknown. [ABSTRACT FROM AUTHOR]

Perivascular epithelioid cell tumors (PEComa)s are mesenchymal neoplasms composed of perivascular epithelioid cells, which express both melanocytic and myogenic markers. These neoplastic cells are thought to arise from undifferentiated cells of the neural crest, or from myoblastic cells harbouring a molecular alteration leading to expression of melanocytic markers, or from pericytic cells. The majority of cases are benign, but a small subset behaves in a malignant fashion. Unfortunately, given their rarity, reliable criteria for predicting malignancy have yet to be established. PEComas of the female genital tract account for nearly 25% of PEComas of all body sites, and the most common site of occurrence is the uterine corpus; less common sites include the cervix, adnexa, vagina/vulva or broad or round ligament exceptionally. The present review aims to elucidate the clinical, pathological and molecular features of gynecological PEComas. Moreover, prognostic and therapeutic implications are also discussed., (© 2020 The Authors. Published by Elsevier Inc.)