Glioblastoma, IDH-wildtype with melanocytic differentiation: An exceedingly rare morphology and immunophenotype.

In spite of extensive research and advances on the molecular biology of melanoma, the process of melanocytic differentiation or its relationship with proliferation is poorly understood. The role of proto-oncogenes in normal melanocyte biology is also intriguing. Proto-oncogene MYC is overexpressed in 40% of melanomas. It has been suggested that MYC can mediate senescence bypass in malignant melanocytes, an important event in melanoma development, likely in cooperation with other oncogenic pathways. However, despite the apparent importance of MYC in melanoma, its functions in normal melanocytes are unknown. We have overexpressed MYC in freshly isolated human primary melanocytes and studied the effects on melanocytic proliferation and differentiation. MYC promoted a transient activation of melanocytes including cell cycle entry, DNA damage and cell migration. Subsequently, MYC induced melanogenesis, increased cellular size and complexity and senescence. Interestingly, we also found strong expression of MYC in regions of human nevi displaying high pigmentation and high expression of senescence marker p16. The results altogether show that MYC drives melanocytic differentiation and suggest that senescence is associated with differentiation. We discuss the implications into the mechanisms governing melanocytic differentiation and the development of melanoma.

Many melanocytic nevi contain areas similar to nerve sheath tumors (NST) and NSTs with melanin have been described. There are some NSTs with at least partial intraneural location, including neurofibromas, plexiform neurofibromas, granular cell tumors and the recently described, dendritic cell neurofibroma with pseudorosettes. We describe the case of an NST with melanocytic differentiation and intraneural location, for which we suggest the term 'melanocytoneuroma' (MCN). It arose in the skin of a 67-year-old woman with no previous history of melanoma or neurofibromatosis. The lesion presented as a papule and histologically consisted of a dermal nodule without junctional melanocytic activity. The lesion comprised an intraneural proliferation of large epithelioid eosinophilic cells with prominent cell borders imparting a 'plant-like' appearance. The cells were also seen within adjacent nerve twigs and were positive for S100, Melan-A, HMB-45, microphthalmia transcription factor and PGP 9.5. The lesion was entirely surrounded by an epithelial membrane antigen-positive-perineurial coat and the individual tumor cells were invested by laminin and collagen type-IV-positive basal lamina-like material. The lesion did not show any evidence of atypia and following complete excision, no recurrence has been documented. In conclusion, this unusual lesion represents an intraneural proliferation with melanocytic and nerve sheath cell differentiation, to which we have accorded the appellation, MCN.

Malignant melanoma can metastasize widely and vary significantly in its histological appearance; it rarely presents as a deep-seated mass without an obvious primary site elsewhere. Malignant peripheral nerve sheath tumor (MPNST) is a high-grade sarcoma characterized by conventional and epithelioid subtypes. MPNST can demonstrate heterologous differentiation, usually in the form of osteosarcomatous, chondrosarcomatous, or rhabdomyosarcomatous differentiation. MPNST does not harbor true melanocytic differentiation, although epithelioid MPNST typically is diffusely S-100 protein positive and superficially can resemble malignant melanoma. An unusual intra-abdominal mass was recently encountered with features of both melanoma and conventional or epithelioid MPNST containing a fascicular spindle cell component, an epithelioid component with melanocytic differentiation, as well as a rhabdomyosarcomatous component. The terminology “malignant neuroectodermal tumor with melanocytic and rhabdomyoblastic differentiation” is proposed to describe this neoplasm, reflecting the unusual concomittant lines of differentiation as well as offering a possible rationale for nosologically challenging aspects of this neoplasm.

Melanocytic differentiation has been described in rare cases of melanin-containing neuroendocrine tumours of the lung [1–5], thyroid [6] and thymus [7]. In some of the cases, neuroendocrine granules and melanosomes were lying free in the cytoplasm of tumour cells, thus indicating true coexpression of melanocytic and neuroendocrine differentiation. On the other hand, neuroendocrine differentiation, consisting in the presence of neuroendocrine granules at ultrastructural level and of intense immunostaining for chromogranin-A and synaptophysin, was described in three cases of cutaneous and mucosal malignant melanomas [8]. Divergent differentiation towards unrelated embryological tissue has been reported in malignant melanoma [9]. So far, cases of neuroendocrine carcinoma with associated melanomatous component in the lung have not been described. There is growing evidence that tumour development may derive from neoplastic transformation of adult stem cells [10]. In a recent publication, it was reported that in the human skin there is a SOX2-positive stem cell capable of differentiation along the neuroendocrine or melanocytic lines [11]. In the present report, we describe the first case of a malignant neoplasm of the lung showing unambiguous differentiation towards neuroendocrine carcinoma and malignant melanoma.

Co-expression of SOX9 and SOX10 during melanocytic differentiation in vitro

The diagnosis of malignant melanoma is sometimes challenging. Immunohistochemistry for specific markers of melanocytic differentiation such as HMB-45 and Melan-A can be very valuable in proving melanocytic differentiation in poorly differentiated or spindled forms of melanoma. Microphthalmia-associated transcription factor (MiTF) is the most recently described and the only nuclear melanocytic marker. This article reviews the biology of MiTF and those published studies that have addressed its diagnostic sensitivity and specificity. MiTF may be very valuable for the diagnosis of melanoma, including desmoplastic variants; melanocytic soft tissue tumors, such as clear cell sarcoma; and the unusual group of tumors that show combined melanocytic and myoid differentiation, the perivascular epithelioid cell family of tumors (PEComas).

<div>Abstract<p><b>Purpose:</b> Clear cell sarcoma (CCS) usually arises in the lower extremities of young adults and is typically associated with a t(12;22) translocation resulting in the fusion of <i>EWS</i> (<i>EWSR1</i>) with <i>ATF1</i>, a gene encoding a member of the cyclic AMP–responsive element binding protein (CREB) family of transcription factors. CCS arising in the gastrointestinal tract is rare and its pathologic and molecular features are not well defined.</p><p><b>Experimental Design:</b> We report a novel variant fusion of <i>EWS</i> to <i>CREB1</i>, a gene at 2q32 encoding another CREB family member highly related to ATF1, detected in three women with gastrointestinal CCS. All three cases contained an identical <i>EWS-CREB1</i> fusion transcript that was shown by reverse transcription-PCR. In two of the cases tested, <i>EWS</i> gene rearrangement was also confirmed by fluorescence <i>in situ</i> hybridization and the <i>EWS-CREB1</i> genomic junction fragments were isolated by long-range DNA PCR.</p><p><b>Results:</b> Morphologically, all three tumors lacked melanin pigmentation. By immunohistochemistry, there was a strong and diffuse S100 protein reactivity, whereas all melanocytic markers were negative. Ultrastructurally, two of the cases lacked melanosomes. The melanocyte-specific transcript of <i>MITF</i> was absent in two cases, and only weakly expressed in the third case. The Affymetrix gene expression data available in one case showed lower expression of the melanocytic genes <i>MITF, TYR</i>, and <i>TYRP1</i>, compared with four <i>EWS-ATF1</i>-positive CCSs of non-gastrointestinal origin.</p><p><b>Conclusions:</b><i>EWS-CREB1</i> may define a novel subset of CCS that occurs preferentially in the gastrointestinal tract and shows little or no melanocytic differentiation. Thus, evidence of melanocytic lineage or differentiation is not a necessary feature of sarcomas with gene fusions involving <i>CREB</i> family members.</p></div>

Clear cell sarcoma (CCS) usually arises in the lower extremities of young adults and is typically associated with a t(12;22) translocation resulting in the fusion of EWS (EWSR1) with ATF1, a gene encoding a member of the cyclic AMP-responsive element binding protein (CREB) family of transcription factors. CCS arising in the gastrointestinal tract is rare and its pathologic and molecular features are not well defined. We report a novel variant fusion of EWS to CREB1, a gene at 2q32 encoding another CREB family member highly related to ATF1, detected in three women with gastrointestinal CCS. All three cases contained an identical EWS-CREB1 fusion transcript that was shown by reverse transcription-PCR. In two of the cases tested, EWS gene rearrangement was also confirmed by fluorescence in situ hybridization and the EWS-CREB1 genomic junction fragments were isolated by long-range DNA PCR. Morphologically, all three tumors lacked melanin pigmentation. By immunohistochemistry, there was a strong and diffuse S100 protein reactivity, whereas all melanocytic markers were negative. Ultrastructurally, two of the cases lacked melanosomes. The melanocyte-specific transcript of MITF was absent in two cases, and only weakly expressed in the third case. The Affymetrix gene expression data available in one case showed lower expression of the melanocytic genes MITF, TYR, and TYRP1, compared with four EWS-ATF1-positive CCSs of non-gastrointestinal origin. EWS-CREB1 may define a novel subset of CCS that occurs preferentially in the gastrointestinal tract and shows little or no melanocytic differentiation. Thus, evidence of melanocytic lineage or differentiation is not a necessary feature of sarcomas with gene fusions involving CREB family members.

<div>Abstract<p><b>Purpose:</b> Clear cell sarcoma (CCS) usually arises in the lower extremities of young adults and is typically associated with a t(12;22) translocation resulting in the fusion of <i>EWS</i> (<i>EWSR1</i>) with <i>ATF1</i>, a gene encoding a member of the cyclic AMP–responsive element binding protein (CREB) family of transcription factors. CCS arising in the gastrointestinal tract is rare and its pathologic and molecular features are not well defined.</p><p><b>Experimental Design:</b> We report a novel variant fusion of <i>EWS</i> to <i>CREB1</i>, a gene at 2q32 encoding another CREB family member highly related to ATF1, detected in three women with gastrointestinal CCS. All three cases contained an identical <i>EWS-CREB1</i> fusion transcript that was shown by reverse transcription-PCR. In two of the cases tested, <i>EWS</i> gene rearrangement was also confirmed by fluorescence <i>in situ</i> hybridization and the <i>EWS-CREB1</i> genomic junction fragments were isolated by long-range DNA PCR.</p><p><b>Results:</b> Morphologically, all three tumors lacked melanin pigmentation. By immunohistochemistry, there was a strong and diffuse S100 protein reactivity, whereas all melanocytic markers were negative. Ultrastructurally, two of the cases lacked melanosomes. The melanocyte-specific transcript of <i>MITF</i> was absent in two cases, and only weakly expressed in the third case. The Affymetrix gene expression data available in one case showed lower expression of the melanocytic genes <i>MITF, TYR</i>, and <i>TYRP1</i>, compared with four <i>EWS-ATF1</i>-positive CCSs of non-gastrointestinal origin.</p><p><b>Conclusions:</b><i>EWS-CREB1</i> may define a novel subset of CCS that occurs preferentially in the gastrointestinal tract and shows little or no melanocytic differentiation. Thus, evidence of melanocytic lineage or differentiation is not a necessary feature of sarcomas with gene fusions involving <i>CREB</i> family members.</p></div>

Embryonal tumor with abundant neuropil and true rosettes (ETANTR) is an increasingly recognized entity that belongs to the family of embryonal tumors of the CNS. The authors present three cases of this rare tumor that were encountered at King Hussein Cancer Center, Amman, Jordan. Discussion of the clinicopathological findings is presented along with a recent literature review. Sixteen-, 57- and 30-month-old children presented with tumors located in the pineal gland, the right fronto- parieto-temporal region and the cerebellum, respectively. The findings of hypocellular neuropil as well as the characteristic ependymoblastic rosettes were seen. In addition the third case showed an abnormal combination of patterns including melanocytic and rhabdomyoblastic differentiation. The tumors stained positively for synaptophysin in the neuropil and small cell component, while the ependymoblastic rosettes stained for vimentin only. Epithelial membrane antigen and CD99 were negative in all components. One of the cases showed tetraploidy of chromosome 2. All cases exhibited an aggressive course. This is a rare and recently recognized tumor with dismal outcome, and reporting of additional new cases should help in gaining more knowledge about it.

Objective: To investigate the clinical, histologic and immunophenotypic features, genetic alterations and prognosis of the rare Xp11 neoplasm with melanocytic differentiation. Methods: Twenty-one cases were selected from the Department of Pathology, Jingling Hospital, Nanjing University School of Medicine from May 2008 to May 2018. The clinicopathologic, immunohistochemical, molecular analysis and follow-up details were collected. Results: There were 7 males and 14 females, with their ages ranging from 4 to 57 years (mean 32.8 years). The tumors were located in kidney (11 cases), pelvis (three cases), and in pancreas, retroperitoneum, adrenal gland, small intestine, prostate, cervix and appendix (one case each). Microscopically, most tumors shared similar morphology such as purely nested or sheet-like architectures separated by a delicate vascular network, purely epithelioid cells with clear to granular eosinophilic cytoplasm, lacks of papillary structures, spindle cell or fat components, uniform round to oval nuclei with small visible nucleoli, and in most of them (16/21) melanin pigment. Immunohistochemically, all cases showed moderately (2+) or strongly (3+) positive staining for TFE3 and Cathepsin K. HMB45 and Melan A were focally expressed in three of 21 cases, while the remaining cases showed typically moderate(2+) or strong (3+) expression. None of the cases were immunoreactive for SMA, desmin, CKpan, S-100 and PAX8. All cases showed TFE3 rearrangement using fluorescence in-situ hybridization (FISH). Fusion FISH assays detected SFPQ-TFE3 gene fusion in 16 cases, NONO-TFE3 gene fusion in two, ASPL-TFE3 and MED15-TFE3 gene fusions in one case each. Polymerase chain reaction and direct sequencing detected SFPQ-TFE3 gene fusion in nine cases, NONO-TFE3 and MED15-TFE3 gene fusions in one case each. Clinical follow-up was available for 15 patients for 12 to 74 months. Six patients died of the disease; and three had recurrences and/or metastases. Six patients were alive with no evidence of disease after initial resection. Conclusions: Xp11 neoplasm with melanocytic differentiation has unique morphologic, immunophenotypic and genetic characteristics. The tumor is aggressive, and should be differentiated from Xp11 translocation RCC and perivascular epithelioid cell tumor.

Preferentially expressed antigen in melanoma (PRAME) is an immunohistochemical biomarker that is diffusely expressed in most cutaneous melanomas and is negative in most benign nevi. Histologically challenging dermal melanocytic neoplasms, such as cellular blue nevi (CBN) and deep penetrating nevi (DPN), and soft tissue tumors with melanocytic differentiation, such as clear cell sarcoma and perivascular epithelioid cell tumor, may resemble primary or metastatic melanoma. PRAME immunohistochemistry (IHC) was applied to archived formalin-fixed, paraffin-embedded specimens of various dermal melanocytic neoplasms and soft tissue neoplasms with melanocytic differentiation. Staining was graded based on the percentage of melanocytes labeled (0-4+ as previously reported). The gold standard was final pathologic diagnosis using histologic, immunophenotypic, and in some cases molecular findings. Fifty-four cases were evaluated. 62.5% (5/8) of blue nevus-like melanomas and 50% (1/2) of DPN-like melanomas were PRAME positive (4+). Of the other tumors, 100% (20/20) of CBN (including 1 atypical CBN with borderline features); 100% (12/12) of DPN, combined DPN, or borderline DPN; 88.9% (8/9) of perivascular epithelioid cell tumors; and 100% (3/3) of clear cell sarcoma were PRAME negative (0-2+). Within the borderline categories specifically, all 8 tumors (1 borderline CBN and 7 borderline DPN) showed low (0-2+) PRAME expression. Overall, the sensitivity for melanoma in this context was 60%, with a specificity of 97.7%. Although our sample size is limited, the results suggest that IHC staining for PRAME may be useful in supporting a diagnosis of melanoma in the setting of challenging dermal melanocytic neoplasms and other epithelioid neoplasms with melanocytic differentiation. However, PRAME IHC lacks sensitivity in this context.

MED15::ATF1-Rearranged Tumor: A Novel Cutaneous Tumor With Melanocytic Differentiation

Although current standards for cancer diagnosis and classification are based primarily on histologic characteristics, progress in molecular genetics during the last few decades has enabled the development of new markers beyond the cellular level. Based on these studies, specific genetic changes have

In addition to melanoma, a large and diverse family of tumors shows melanocytic differentiation. The best characterized member of this family is clear cell sarcoma, which is characterized by EWSR1::ATF1 and EWSR1::CREB1 fusions. These fusions drive the transcription of MITF, the master regulator of melanocytic differentiation. Clear cell tumor with melanocytic differentiation and MITF::CREM translocation is a recently described tumor with some similarities to clear cell sarcoma. However, only a single case has been reported. Here, we describe a second molecularly proven case that arose on the scalp of a newborn baby. In contrast to the prior reported case, the current case showed predominantly high-grade cytomorphologic features with only focal clear cell areas. Similar to the prior case, the tumor showed immunohistochemical evidence of neural crest origin/differentiation with prominent melanocytic differentiation. The fusion breakpoints were also similar and preserved the transcriptional activation domain of CREM, suggesting that CREM hyperactivity is a major feature of this tumor type. The current tumor showed a short-interval recurrence. These results expand the clinical and pathologic spectrum of this potentially new entity.