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Abstract：
BACKGROUND: Cutaneous Melanocytic Tumor with CRTC1::TRIM11 Fusion (CMTCT) represents a novel and rare entity in the realm of dermatological oncology, characterized by distinct melanocytic differentiation. This particular tumor type has yet to be officially recognized by the World Health Organization (WHO). CMTCT is generally perceived as a tumor with a relatively indolent nature; however, it is not devoid of metastatic potential. Therefore, ensuring complete surgical excision of the tumor, coupled with rigorous long-term follow-up, is paramount for patient management. In this context, we report the case of an 18-year-old female patient who presented with a dull red nodule on her left leg. Initial surgical intervention led to a pathological diagnosis of CMTCT, but it was determined that the tumor had not been fully excised. Consequently, a second surgical procedure was undertaken to achieve complete removal of the tumor. During a follow-up period of six months post-surgery, the patient showed no signs of local recurrence or metastasis, indicating a successful outcome.
METHODS: An 18-year-old female patient noticed a dull red nodule on her left leg three years ago, which exhibited slow growth over time. She underwent a subcutaneous tumor resection. Histological examination under high-power magnification revealed that the neoplasm consisted of epithelioid cells arranged in nests, fascicles, bundles, or sheets. The tumor cells had round or ovoid nuclei with prominent nucleoli and visible mitotic figures. Notably, areas resembling nevus cell clusters were observed. Immunohistochemical analysis confirmed melanocytic differentiation. Next-generation sequencing (NGS) identified a CRTC1::TRIM11 fusion, and fluorescence in situ hybridization (FISH) for CRTC1 confirmed rearrangement. Consequently, a diagnosis of cutaneous melanocytic tumor with CRTC1::TRIM11 fusion was established.
CONCLUSIONS: CMTCT is a rare tumor characterized by melanocytic differentiation. In this case, the tumor predominantly comprised epithelioid cells with localized nevus cell clusters. The expression of melanocyte markers could easily lead to a misdiagnosis as cutaneous melanoma. However, several distinguishing features were noted: the tumor was not connected to the epidermis, exhibited low cellular heterogeneity and proliferation index, and showed minimal cellular atypia. Additionally, tests for EWSR1 rearrangement (FISH) and BRAF V600E mutation (PCR-ARMS) were negative.This case underscores the importance of a comprehensive diagnostic approach when clinical, microscopic, immunohistochemical, and molecular findings do not align. The presence of nevus cell clusters morphology in the tumor cells enhances our understanding of this disease\'s histological spectrum and aids in avoiding misdiagnosis or missed diagnosis.
METHODS: An 18-year-old female patient noticed a dull red nodule on her left leg three years ago, which exhibited slow growth over time. She underwent a subcutaneous tumor resection. Histological examination under high-power magnification revealed that the neoplasm consisted of epithelioid cells arranged in nests, fascicles, bundles, or sheets. The tumor cells had round or ovoid nuclei with prominent nucleoli and visible mitotic figures. Notably, areas resembling nevus cell clusters were observed. Immunohistochemical analysis confirmed melanocytic differentiation. Next-generation sequencing (NGS) identified a CRTC1::TRIM11 fusion, and fluorescence in situ hybridization (FISH) for CRTC1 confirmed rearrangement. Consequently, a diagnosis of cutaneous melanocytic tumor with CRTC1::TRIM11 fusion was established.
CONCLUSIONS: CMTCT is a rare tumor characterized by melanocytic differentiation. In this case, the tumor predominantly comprised epithelioid cells with localized nevus cell clusters. The expression of melanocyte markers could easily lead to a misdiagnosis as cutaneous melanoma. However, several distinguishing features were noted: the tumor was not connected to the epidermis, exhibited low cellular heterogeneity and proliferation index, and showed minimal cellular atypia. Additionally, tests for EWSR1 rearrangement (FISH) and BRAF V600E mutation (PCR-ARMS) were negative.This case underscores the importance of a comprehensive diagnostic approach when clinical, microscopic, immunohistochemical, and molecular findings do not align. The presence of nevus cell clusters morphology in the tumor cells enhances our understanding of this disease\'s histological spectrum and aids in avoiding misdiagnosis or missed diagnosis.
摘要：
背景：带有CRTC1的皮肤黑素细胞肿瘤::TRIM11融合（CMTCT）代表了皮肤肿瘤学领域的一种新颖而罕见的实体，以明显的黑素细胞分化为特征。这种特殊的肿瘤类型尚未得到世界卫生组织(WHO)的正式承认。CMTCT通常被认为是具有相对惰性性质的肿瘤；然而，它并非没有转移潜力。因此,确保完整的手术切除肿瘤，再加上严格的长期随访，对于患者管理至关重要。在这种情况下，我们报道了一例18岁女性患者，她的左腿上有一个暗红色结节。最初的手术干预导致CMTCT的病理诊断，但确定肿瘤尚未完全切除。因此,进行第二次外科手术以实现肿瘤的完全切除。在术后六个月的随访期间，患者没有出现局部复发或转移的迹象,表明一个成功的结果。
方法：一名18岁的女性患者3年前发现她的左腿上有一个暗淡的红色结节，随着时间的推移表现出缓慢的增长。她接受了皮下肿瘤切除术。高倍镜下的组织学检查显示肿瘤由排列在巢中的上皮样细胞组成，成束,捆绑包，或床单。肿瘤细胞具有圆形或卵形核，具有明显的核仁和可见的有丝分裂图。值得注意的是,观察到类似痣细胞簇的区域。免疫组织化学分析证实黑素细胞分化。下一代测序（NGS）确定了CRTC1::TRIM11融合，CRTC1的荧光原位杂交（FISH）证实了重排。因此,建立了CRTC1::TRIM11融合皮肤黑素细胞肿瘤的诊断。
结论：CMTCT是一种以黑色素细胞分化为特征的罕见肿瘤。在这种情况下,肿瘤主要由上皮样细胞和局部痣细胞簇组成。黑素细胞标志物的表达容易导致误诊为皮肤黑色素瘤。然而,注意到几个明显的特征：肿瘤与表皮没有连接，表现出低细胞异质性和增殖指数，并显示出轻微的细胞异型性。此外,EWSR1重排(FISH)和BRAFV600E突变(PCR-ARMS)检测结果均为阴性.这个案例强调了临床时，全面诊断方法的重要性，微观,免疫组织化学，和分子研究结果不一致。肿瘤细胞中痣细胞簇形态的存在增强了我们对这种疾病的组织学谱的理解，并有助于避免误诊或漏诊。
方法：一名18岁的女性患者3年前发现她的左腿上有一个暗淡的红色结节，随着时间的推移表现出缓慢的增长。她接受了皮下肿瘤切除术。高倍镜下的组织学检查显示肿瘤由排列在巢中的上皮样细胞组成，成束,捆绑包，或床单。肿瘤细胞具有圆形或卵形核，具有明显的核仁和可见的有丝分裂图。值得注意的是,观察到类似痣细胞簇的区域。免疫组织化学分析证实黑素细胞分化。下一代测序（NGS）确定了CRTC1::TRIM11融合，CRTC1的荧光原位杂交（FISH）证实了重排。因此,建立了CRTC1::TRIM11融合皮肤黑素细胞肿瘤的诊断。
结论：CMTCT是一种以黑色素细胞分化为特征的罕见肿瘤。在这种情况下,肿瘤主要由上皮样细胞和局部痣细胞簇组成。黑素细胞标志物的表达容易导致误诊为皮肤黑色素瘤。然而,注意到几个明显的特征：肿瘤与表皮没有连接，表现出低细胞异质性和增殖指数，并显示出轻微的细胞异型性。此外,EWSR1重排(FISH)和BRAFV600E突变(PCR-ARMS)检测结果均为阴性.这个案例强调了临床时，全面诊断方法的重要性，微观,免疫组织化学，和分子研究结果不一致。肿瘤细胞中痣细胞簇形态的存在增强了我们对这种疾病的组织学谱的理解，并有助于避免误诊或漏诊。
