title: Crater/ulcerated form of infundibular squamous cell carcinoma: A possible distinct entity as a malignant (or high-grade) counterpart to keratoacanthoma.
abstract: Follicular squamous cell carcinoma (SCC) with infundibular differentiation includes the common and crater forms of infundibular SCC. We previously considered the crater/ulcerated infundibular SCC to be a progressive condition of the common form and histopathologically studied an additional five cases of the crater/ulcerated infundibular SCC, the results of which suggested the following characteristic histopathological features and possible developmental process in this type of SCC: (i) a considerable number of continuous hyperplastic follicular infundibula, which may develop at the beginning of the disease; (ii) hyperplastic infundibula exhibiting an abrupt or gradual transition to the SCC component, which frequently change relative to the neoplastic infundibular canal; and (iii) the presence of multiple sites of branching of the neoplastic infundibular canals and/or complete involvement of large cysts in the neoplastic process over the center of the lesion, resulting in ulceration. Based on these histopathological findings, we considered that crater/ulcerated infundibular SCC involve a considerable number of continuous follicular infundibula from the start, although some cases may develop from the common form. We also emphasize the possible aggressive biological behavior of the crater/ulcerated form. Keratoacanthoma (KA) is a unique, benign or borderline malignant neoplasm exhibiting follicular (infundibular/isthmic) differentiation characterized by the involvement of continuous follicular infundibula in multiples. From this standpoint, we consider that crater/ulcerated infundibular SCC is possibly related to KA in terms of histogenesis and is a malignant (or high-grade) counterpart of KA.
authors: Division of Dermatology, Department of Internal Medicine, Faculty of Medicine, Saga University, Saga, Japan.
authors: Noriyuki
authors: N
authors: Misago
authors: Division of Dermatology, Department of Internal Medicine, Faculty of Medicine, Saga University, Saga, Japan.
authors: Takuya
authors: T
authors: Inoue
authors: Division of Dermatology, Department of Internal Medicine, Faculty of Medicine, Saga University, Saga, Japan.
authors: Kotaro
authors: K
authors: Nagase
authors: Division of Dermatology, Department of Internal Medicine, Faculty of Medicine, Saga University, Saga, Japan.
authors: Noriko
authors: N
authors: Tsuruta
authors: Division of Dermatology, Department of Internal Medicine, Faculty of Medicine, Saga University, Saga, Japan.
authors: Akiko
authors: A
authors: Tara-Hashimoto
authors: Division of Dermatology, Department of Internal Medicine, Faculty of Medicine, Saga University, Saga, Japan.
authors: Hiromi
authors: H
authors: Kimura
authors: Division of Dermatology, Department of Internal Medicine, Faculty of Medicine, Saga University, Saga, Japan.
authors: Kanako
authors: K
authors: Takahara
authors: Division of Dermatology, Department of Internal Medicine, Faculty of Medicine, Saga University, Saga, Japan.
authors: Tomomi
authors: T
authors: Narita
authors: Division of Dermatology, Department of Internal Medicine, Faculty of Medicine, Saga University, Saga, Japan.
authors: Yutaka
authors: Y
authors: Narisawa
mesh_terms: D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D002454:Cell Differentiation; D002471:Cell Transformation, Neoplastic; D005153:Facial Neoplasms / Q000473:pathology*; D005260:Female; D006801:Humans; D007636:Keratoacanthoma / Q000473:pathology*; D008297:Male; D012878:Skin Neoplasms / Q000473:pathology*; D012883:Skin Ulcer / Q000209:etiology
keywords: follicular squamous cell carcinoma; infundibular squamous cell carcinoma; keratoacanthoma; keratoacanthoma with malignant transformation; keratoacanthoma-like squamous cell carcinoma