{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T20:41:36Z","timestamp":1779914496812,"version":"3.53.1"},"reference-count":25,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2021,10,7]],"date-time":"2021-10-07T00:00:00Z","timestamp":1633564800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Diagnostics"],"abstract":"<jats:p>We present histopathological criteria for diagnosing keratoacanthoma (KA). In KA, four histological stages are recognized, which are the early\/proliferative stage, well-developed stage, regressing stage and regressed stage. In diagnosing KA, we emphasize that KA consists of the proliferation of enlarged pale pink cells with ground glass-like cytoplasm without nuclear atypia, other than crateriform architecture. KA sometimes exhibits malignant transformation within the lesions. We describe the characteristics of benign and malignant epithelial crateriform tumors that should be differentiated from KA. We also present the data of histopathological diagnosis of lesions clinically diagnosed as KA, its natural course and related lesions after partial biopsy, and incidence of crateriform epithelial neoplasms. Based on these data, we recommend complete excision of the lesion when KA is clinically suspected, especially when the lesion is located on a sun-exposed area of an elderly patient. If complete excision is impossible, partial excision of a sufficient specimen with intact architecture is required. In such a case, however, careful investigation after biopsy will be needed, even if the histopathological diagnosis is KA, because there is some possibility that a conventional SCC lesion remains in the residual tissue.<\/jats:p>","DOI":"10.3390\/diagnostics11101848","type":"journal-article","created":{"date-parts":[[2021,10,7]],"date-time":"2021-10-07T09:24:04Z","timestamp":1633598644000},"page":"1848","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["What Is a Solitary Keratoacanthoma? A Benign Follicular Neoplasm, Frequently Associated with Squamous Cell Carcinoma"],"prefix":"10.3390","volume":"11","author":[{"given":"Azusa","family":"Ogita","sequence":"first","affiliation":[{"name":"Division of Dermatology and Dermatopathology, Nippon Medical School Musashi Kosugi Hospital, Kawasaki 211-8533, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7036-7084","authenticated-orcid":false,"given":"Shin-ichi","family":"Ansai","sequence":"additional","affiliation":[{"name":"Division of Dermatology and Dermatopathology, Nippon Medical School Musashi Kosugi Hospital, Kawasaki 211-8533, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,10,7]]},"reference":[{"key":"ref_1","unstructured":"Elder, D.E., Massi, D., Scolyer, R.A., and Willemze, R. (2018). Squamous cell carcinoma. World Health Organization Classification of Tumours, IARC Press. [4th ed.]."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2317","DOI":"10.3390\/curroncol28040213","article-title":"Local chemotherapy as an adjuvant treatment in unresectable squamous cell carcinoma: What do we know so far?","volume":"28","author":"Bennardo","year":"2021","journal-title":"Curr. Oncol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"487","DOI":"10.1111\/bjd.20389","article-title":"A clinical and biological review of keratoacanthoma","volume":"185","author":"Tisak","year":"2021","journal-title":"Br. J. Dermatol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"208","DOI":"10.1159\/000018276","article-title":"Differentiating squamous cell carcinoma from keratoacanthoma using histopathological criteria. Is it possible? A study of 296 cases","volume":"199","author":"Cribier","year":"1999","journal-title":"Dermatology"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"332","DOI":"10.1097\/00000372-199308000-00007","article-title":"Solitary keratoacanthoma is a squamous-cell carcinoma: Three examples with metastasis","volume":"15","author":"Hodak","year":"1993","journal-title":"Am. J. Dermatopathol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"899","DOI":"10.1111\/j.1346-8138.2005.tb00868.x","article-title":"Possible spontaneous regression of a metastatic lesion of keratoacanthoma-like squamous cell carcinoma in a regional lymph node","volume":"32","author":"Ansai","year":"2005","journal-title":"J. Dermatol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"617","DOI":"10.1111\/cup.12350","article-title":"The histopathologic changes in keratoacanthoma depend on its stage","volume":"41","author":"Misago","year":"2014","journal-title":"J. Cutan. Pathol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"437","DOI":"10.1111\/cup.12317","article-title":"The changes in the expression levels of follicular markers in keratoacanthoma depend on the stage: Keratoacanthoma is a follicular neoplasm exhibiting infundibular\/isthmic differentiation without expression of CK15","volume":"41","author":"Misago","year":"2014","journal-title":"J. Cutan. Pathol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"443","DOI":"10.1111\/1346-8138.12104","article-title":"Keratoacanthoma and other types of squamous cell carcinoma with crateriform architecture: Classification and identification","volume":"40","author":"Misago","year":"2013","journal-title":"J. Dermatol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"353","DOI":"10.1111\/1346-8138.12784","article-title":"Natural course of keratoacanthoma and related lesions after partial biopsy: The clinical analysis of the 66 lesions","volume":"42","author":"Takai","year":"2015","journal-title":"J. Dermatol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"667","DOI":"10.1111\/1346-8138.12871","article-title":"Crater\/ulcerated form of infundibular squamous cell carcinoma: A possible distinct entity as a malignant (or high-grade) counterpart to keratoacanthoma","volume":"42","author":"Misago","year":"2015","journal-title":"J. Dermatol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1321","DOI":"10.1111\/1346-8138.13390","article-title":"Histopathological diagnosis of epithelial crateriform tumors: Keratoacanthoma and other epithelial crateriform tumors","volume":"43","author":"Ogita","year":"2016","journal-title":"J. Dermatol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"304","DOI":"10.1111\/1346-8138.13696","article-title":"Advances in histopathological diagnosis of keratoacanthoma","volume":"44","author":"Takai","year":"2017","journal-title":"J. Dermatol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"803","DOI":"10.1111\/1346-8138.13787","article-title":"Keratoacanthoma en plaque\/nodule: A brief report of the clinicopathological features of five cases","volume":"44","author":"Misago","year":"2017","journal-title":"J. Dermatol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"305","DOI":"10.1097\/00000372-200008000-00002","article-title":"Solitary keratoacanthoma: A self-healing proliferation that frequently becomes malignant","volume":"22","author":"Requena","year":"2000","journal-title":"Am. J. Dermatopathol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"423","DOI":"10.1097\/DAD.0b013e3181c4340a","article-title":"Squamous cell carcinoma arising in keratoacanthoma: A neglected phenomenon in the elderly","volume":"32","author":"Weedon","year":"2010","journal-title":"Am. J. Dermatopathol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1154","DOI":"10.1111\/1346-8138.13331","article-title":"Clinicopathological study of crateriform verruca: Crateriform epithelial lesions histopathologically distinct from keratoacanthoma","volume":"43","author":"Ogita","year":"2016","journal-title":"J. Dermatol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"543","DOI":"10.1097\/00000372-199610000-00015","article-title":"Trichilemmal keratosis. A clinicopathologic and immunohistochemical study of two cases","volume":"18","author":"Poblet","year":"1996","journal-title":"Am. J. Dermatopathol."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1111\/j.1600-0560.1983.tb00316.x","article-title":"Trichilemmal keratosis (horn): A light and electron microscopic study","volume":"10","author":"Kimura","year":"1983","journal-title":"J. Cutan. Pathol."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"395","DOI":"10.1097\/01.dad.0000211518.65057.35","article-title":"Papillated Bowen disease, a distinct variant","volume":"28","author":"Sun","year":"2006","journal-title":"Am. J. Dermatopathol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1046\/j.0303-6987.2004.0134.x","article-title":"Follicular squamous cell carcinoma of the skin: A poorly recognized neoplasm arising from the wall of hair follicles","volume":"31","author":"Borghi","year":"2004","journal-title":"J. Cutan. Pathol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"127","DOI":"10.1097\/DAD.0b013e318161310c","article-title":"Keratoacanthoma and infundibulocystic squamous cell carcinoma","volume":"30","author":"Kossard","year":"2008","journal-title":"Am. J. Dermatopathol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"687","DOI":"10.1097\/DAD.0b013e318205b2c5","article-title":"Infundibular (follicular) and infundibulocystic squamous cell carcinoma: A clinicopathological and immunohistochemical study","volume":"33","author":"Misago","year":"2011","journal-title":"Am. J. Dermatopahtol."},{"key":"ref_24","first-page":"1775","article-title":"Histopathological diagnosis of lesions clinically diagnosed as keratoacanthoma","volume":"123","author":"Ansai","year":"2013","journal-title":"Jpn. J. Dermmtol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"e288","DOI":"10.1111\/1346-8138.15889","article-title":"Japanese dermatological association guidelines: Outlines of guidelines for cutaneous squamous cell carcinoma 2020","volume":"48","author":"Ansai","year":"2021","journal-title":"J. Dermatol."}],"container-title":["Diagnostics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2075-4418\/11\/10\/1848\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:10:07Z","timestamp":1760166607000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2075-4418\/11\/10\/1848"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,10,7]]},"references-count":25,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2021,10]]}},"alternative-id":["diagnostics11101848"],"URL":"https:\/\/doi.org\/10.3390\/diagnostics11101848","relation":{},"ISSN":["2075-4418"],"issn-type":[{"value":"2075-4418","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,10,7]]}}}