{"doi":"10.1016/j.jdcr.2020.02.021","title":"Basal cell carcinoma and balloon cell nevus collision mimicking a melanoma on reflectance confocal microscopy","abstract":"A preexisting intradermal nevus (IDN) on the chest of a 30-year-old patient changed compared with her baseline total body photography. Clinical examination found a 6-mm shiny pink papule (Fig 1, inset). Clinical differential diagnosis included irritated IDN, basal cell carcinoma (BCC), nodular melanoma, nevoid melanoma, and melanoma arising in a nevus. Dermoscopy showed arborizing vessels characteristic of a BCC (Fig 1). Based on the history, the differential diagnosis expanded to include a collision between a BCC and an IDN. Reflectance confocal microscopy (RCM) showed focal areas of lobulated dermal tumor islands with palisading and peritumoral clefting, features diagnostic of BCC (Fig 2, A). Adjacent to the BCC nodules there were nonhomogeneous round nucleated cells with variable size and cytoplasmic brightness (Fig 2, A), features suggestive of melanocytic neoplasia. In addition, nonhomogeneous dense and sparse nests composed of large bright pleomorphic cells were present in the lower epidermis and superficial dermis (Fig 2, B), features concerning for invasive amelanotic melanoma with pagetoid spread. A collision between BCC and IDN was identified (Fig 3); however, the pagetoid-appearing melanocytes that confounded the diagnosis of melanoma on RCM were identified as balloon cells within the most superficial area of the IDN. Although the presence of aggregated white1Jaimes N. Braun R.P. Stolz W. Busam K.J. Marghoob A.A. White globules correlate with balloon cell nevi nests.J Am Acad Dermatol. 2011; 65: e119-e120Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar,2Jaimes N. Scope A. Welzel J. et al.White globules in melanocytic neoplasms: in vivo and ex vivo characteristics.Dermatol Surg. 2012; 38: 128-132Crossref PubMed Scopus (7) Google Scholar to yellow globules3Cinotti E. Perrot J.L. Labeille B. Douchet C. Thuret G. Cambazard F. Yellow globules in balloon cell naevus.Australas J Dermatol. 2013; 54: 268-270Crossref PubMed Scopus (12) Google Scholar in a nevus is the hallmark of balloon cell nevus (BCN) on dermoscopy, not all melanocytic lesions with balloon cells will have this feature as evident in our case. Only 1 case report documents the RCM features of BCN as homogenous dense nests with bright and vacuolated cytoplasm.4Larre Borges A. Zalaudek I. Longo C. et al.Melanocytic nevi with special features: clinical-dermoscopic and reflectance confocal microscopic-findings.J Eur Acad Dermatol Venereol. 2014; 28: 833-845Crossref PubMed Scopus (31) Google Scholar Here we describe a case of BCC colliding with an IDN in which balloon cell changes mimicked melanoma with pagetoid spread. The history, clinical, dermoscopy, and RCM findings culminated in a broad differential diagnosis. Based on classical clinical morphology of an IDN and stability of the nevus for more than 5 years of follow-up, we were confident that the original lesion was an IDN. However, the lack of yellow/white globules on dermoscopy precluded us from contemplating the diagnosis of BCN.1Jaimes N. Braun R.P. Stolz W. Busam K.J. Marghoob A.A. White globules correlate with balloon cell nevi nests.J Am Acad Dermatol. 2011; 65: e119-e120Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar, 2Jaimes N. Scope A. Welzel J. et al.White globules in melanocytic neoplasms: in vivo and ex vivo characteristics.Dermatol Surg. 2012; 38: 128-132Crossref PubMed Scopus (7) Google Scholar, 3Cinotti E. Perrot J.L. Labeille B. Douchet C. Thuret G. Cambazard F. Yellow globules in balloon cell naevus.Australas J Dermatol. 2013; 54: 268-270Crossref PubMed Scopus (12) Google Scholar The observed clinical change within this preexisting nevus raised concern for melanoma arising in a nevus; however, the dermoscopy feature of arborizing vessels suggested a BCC-IDN collision. RCM was performed to determine whether this was a melanoma arising in a nevus or a collision between an IDN and BCC. In addition to identifying dermal BCC tumor nodules and monomorphic nucl","journal":"JAAD Case Reports","year":2020,"id":113944,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":2,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9559,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2020-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":369164,"name":"Cristina Carrera","orcid":"0000-0003-1608-8820","position":1,"is_corresponding":false},{"id":366216,"name":"Ashfaq A. Marghoob","orcid":"0000-0001-6068-0114","position":2,"is_corresponding":false},{"id":442327,"name":"Manu Jain","orcid":"0000-0002-6035-0825","position":0,"is_corresponding":true}],"reference_count":4,"raw_metadata":null,"created_at":"2026-07-18T23:13:25.964732Z","pmid":"32258315","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}