Crater/ulcerated form of infundibular squamous cell carcinoma: A possible distinct entity as a malignant (or high‐grade) counterpart to keratoacanthoma |
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| Authors: | Noriyuki Misago Takuya Inoue Kotaro Nagase Noriko Tsuruta Akiko Tara‐Hashimoto Hiromi Kimura Kanako Takahara Tomomi Narita Yutaka Narisawa |
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| Affiliation: | Division of Dermatology, Department of Internal Medicine, Faculty of Medicine, Saga University, Saga, Japan |
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| 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. |
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| Keywords: | follicular squamous cell carcinoma infundibular squamous cell carcinoma keratoacanthoma keratoacanthoma with malignant transformation keratoacanthoma‐like squamous cell carcinoma |
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