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Donati M, Kazakov DV. Beyond typical histology of BAP1-inactivated melanocytoma. Pathol Res Pract 2024; 259:155162. [PMID: 38326181 DOI: 10.1016/j.prp.2024.155162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 01/05/2024] [Accepted: 01/20/2024] [Indexed: 02/09/2024]
Abstract
BAP1-inactivated melanocytoma (BIM) is a novel subgroup of melanocytic neoplasm listed in the 5th edition of WHO classification of skin tumor. BIM is characterized by two molecular alterations, including a mitogenic driver mutation (usually BRAF gene) and the loss of function of BAP1, a tumor suppressor gene located on chromosome 3p21, which encodes for BRCA1-associated protein (BAP1). The latter represents a nuclear-localized deubiquitinase involved in several cellular processes including cell cycle regulation, chromatin remodeling, DNA damage response, differentiation, senescence and cell death. BIMs are histologically characterized by a population of large epithelioid melanocytes with well-demarcated cytoplasmic borders and copious eosinophilic cytoplasm, demonstrating loss of BAP1 nuclear expression by immunohistochemistry. Recently, we have published a series of 50 cases, extending the morphological spectrum of the neoplasm and highlighting some new microscopic features. In the current article, we focus on some new histological features, attempting to explain and link them to certain mechanisms of tumor development, including senescence, endoreplication, endocycling, asymmetric cytokinesis, entosis and others. In light of the morphological and molecular findings observed in BIM, we postulated that this entity unmasks a fine mechanism of tumor in which both clonal/stochastic and hierarchical model can be unified.
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Affiliation(s)
- Michele Donati
- Department of Pathology, Fondazione Policlinico Universitario Campus Bio-Medico, Rome, Italy; Department of Pathology, Università Campus Bio-Medico di Roma, Via Alvaro del Portillo, 21 - 00128 Roma, Italy.
| | - Dmitry V Kazakov
- IDP Dermatohistopathologie Institut, Pathologie Institut Enge, Zurich, Switzerland
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Abstract
PURPOSE OF REVIEW Recognition of skin findings associated with tumor predisposition syndromes can prompt early evaluation and surveillance and improve management. Additionally, knowing when to test and when to defer performing genetic testing can streamline management. This article reviews tumor predisposition syndromes with recently characterized skin findings and disorders for which early recognition and counseling can impact the course of disease. RECENT FINDINGS Café au lait macules (CALMs) are important in many tumor predisposition syndromes, and 'atypical' CALMs are associated with constitutional mismatch repair deficiency and Fanconi anemia. Melanoma predisposition syndromes caused by pathogenic variants in POT1 and BAP1 are more recently described, and both are associated with Spitzoid tumors. Somatic pathogenic variants can cause segmental nevoid basal cell carcinoma syndrome and a mosaic form of Peutz-Jeghers syndrome. Patients with PTEN hamartoma syndrome have increased risk for melanoma but this might not occur until adulthood. SUMMARY The cutaneous manifestations of tumor predisposition syndromes can aid diagnosis. Early photoprotection is key to modifying a main risk factor for skin cancer in many of these syndromes. Implementing surveillance guidelines facilitates early detection of tumors.
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Donati M, Martinek P, Steiner P, Grossmann P, Vanecek T, Kastnerova L, Kolm I, Baneckova M, Donati P, Kletskaya I, Kalmykova A, Feit J, Blasch P, Szilagyi D, Baldi A, Persichetti P, Crescenzi A, Michal M, Kazakov DV. Novel insights into the BAP1-inactivated melanocytic tumor. Mod Pathol 2022; 35:664-675. [PMID: 34857909 DOI: 10.1038/s41379-021-00976-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 11/10/2021] [Accepted: 11/10/2021] [Indexed: 11/09/2022]
Abstract
BAP1-inactivated melanocytic tumor (BIMT) is a group of melanocytic neoplasms with epithelioid cell morphology molecularly characterized by the loss of function of BAP1, a tumor suppressor gene located on chromosome 3p21, and a mutually exclusive mitogenic driver mutation, more commonly BRAF. BIMTs can occur as a sporadic lesion or, less commonly, in the setting of an autosomal dominant cancer susceptibility syndrome caused by a BAP1 germline inactivating mutation. Owing to the frequent identification of remnants of a conventional nevus, BIMTs are currently classified within the group of combined melanocytic nevi. "Pure" lesions can also be observed. We studied 50 BIMTs from 36 patients. Most lesions were composed of epithelioid melanocytes of varying size and shapes, resulting extreme cytomorphological heterogeneity. Several distinctive morphological variants of multinucleated/giant cells were identified. Some hitherto underrecognized microscopic features, especially regarding nuclear characteristics included nuclear blebbing, nuclear budding, micronuclei, shadow nuclei, peculiar cytoplasmic projections (ant-bear cells) often containing micronuclei and cell-in-cell structures (entosis). In addition, there were mixed nests of conventional and BAP1-inactivated melanocytes and squeezed remnants of the original nevus. Of the 26 lesions studied, 24 yielded a BRAF mutation, while in the remaining two cases there was a RAF1 fusion. BAP1 biallelic and singe allele mutations were found in 4/22 and 16/24 neoplasms, respectively. In five patients, there was a BAP1 germline mutation. Six novel, previously unreported BAP1 mutations have been identified. BAP1 heterozygous loss was detected in 11/22 lesions. Fluorescence in situ hybridization for copy number changes revealed a related amplification of both RREB1 and MYC genes in one tumor, whereas the remaining 20 lesions studied were negative; no TERT-p mutation was found in 14 studied neoplasms. Tetraploidy was identified in 5/21 BIMTs. Of the 21 patients with available follow-up, only one child had a locoregional lymph node metastasis. Our results support a progression of BIMTs from a conventional BRAF mutated in which the original nevus is gradually replaced by epithelioid BAP1-inactivated melanocytes. Some features suggest more complex underlying pathophysiological events that need to be elucidated.
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Affiliation(s)
- Michele Donati
- Department of Pathology, University Hospital Campus Bio-Medico, Rome, Italy.,Sikl's Department of Pathology, Medical Faculty in Pilsen, Charles University in Prague, Pilsen, Czech Republic
| | | | | | | | | | - Liubov Kastnerova
- Sikl's Department of Pathology, Medical Faculty in Pilsen, Charles University in Prague, Pilsen, Czech Republic.,Bioptical Laboratory, Pilsen, Czech Republic
| | - Isabel Kolm
- Department of Dermatology, University Hospital of Zurich, Zurich, Switzerland
| | - Martina Baneckova
- Sikl's Department of Pathology, Medical Faculty in Pilsen, Charles University in Prague, Pilsen, Czech Republic.,Bioptical Laboratory, Pilsen, Czech Republic
| | | | - Irina Kletskaya
- Russian Children's Clinical Hospital of Pirogov Russian National Research Medical University of the Ministry of Healthcare, Russian Federation, Moscow, Russia
| | | | - Josef Feit
- Institute of Pathology, University of Ostrava, Ostrava, Czech Republic
| | - Petr Blasch
- Department of Pathology, Regional Hospital, Hranice, Czech Republic
| | - Diana Szilagyi
- Department of Pathology, Emergency Clinical County Hospital "Pius Brinzeu", Timisoara, Romania
| | - Alfonso Baldi
- Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, University of Campania "Luigi Vanvitelli", Caserta, Italy
| | - Paolo Persichetti
- Department of Plastic, Reconstructive and Aesthetic Surgery, Campus Bio-Medico di Roma University, Rome, Italy
| | - Anna Crescenzi
- Department of Pathology, University Hospital Campus Bio-Medico, Rome, Italy
| | - Michal Michal
- Sikl's Department of Pathology, Medical Faculty in Pilsen, Charles University in Prague, Pilsen, Czech Republic.,Bioptical Laboratory, Pilsen, Czech Republic
| | - Dmitry V Kazakov
- Sikl's Department of Pathology, Medical Faculty in Pilsen, Charles University in Prague, Pilsen, Czech Republic. .,Department of Dermatology, University Hospital of Zurich, Zurich, Switzerland.
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