Keratoacanthoma and other types of squamous cell carcinoma with crateriform architecture: Classification and identification

Abstract

The terminology and classification of keratoacanthoma (KA) and other types of squamous cell carcinoma (SCC) with crateriform architecture have not been clarified. The study evaluated the clinicopathological features of 41 nodular (exo-endophytic) SCC lesions with a central keratin-filled crater, including KA (well-developed stage). The lesions were histopathologically classified into six categories: (i) KA (well-developed stage) (27 lesions); (ii) KA-like SCC (three lesions); (iii) KA with malignant transformation (three lesions); (iv) infundibular SCC (crateriform) (four lesions); (v) crateriform SCC arisen from actinic keratosis (three lesions); and (vi) crateriform Bowen's disease (one lesion). The true characteristics of KA-like SCC remain unresolved, but there are three possibilities, namely, that it is one step in the evolution of KA, it is a borderline lesion between KA and invasive SCC, or it is one form of "KA with malignant transformation". KA, KA-like SCC, KA with malignant transformation and infundibular SCC (crater form) are considered to be hair follicle-related neoplasms. In contrast, crateriform SCC arisen from actinic keratosis and crateriform Bowen's disease are SCC, which are not related either to the hair follicles or KA. From an etiological standpoint, the presented lesions in these six categories are considered to be mixed up due to the similarity of crateriform architecture between the various types of lesions. However, the information provided in this report is intended to help physicians to make an accurate differential diagnosis of these conditions in clinical practice. The present study provides an opportunity to standardize the terminology for KA and related neoplasms.

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

“…2 -4,9,12,31 -34 During the process of this careful selection, we eliminated the following cases: (i) 'KA-like SCCs (five lesions)' 35 -37 that histopathologically resembled KA but had an eccentric architecture and prominent atypical cytological features, (ii) 'infundibular and infundibulocystic SCCs (11 lesions)' which have been described elsewhere, 38 and diagnostically challenging cases (six lesions) with regard to whether the lesion was a very early stage of KA or infundibular and infundibulocystic SCC, (iii) 'KA associated with SCC/KA with malignant transformation (four lesions)', 6,7,37 (iv) crateriform SCC arisen from actinic keratosis (four lesions), 6,37 and (v) crateriform Bowen's disease (one lesion). 37 After this careful selection, a total of 67 'pure' KAs, including 16 early or proliferative stage lesions, 43 well-developed stage lesions, five regressing stage lesions and three regressed stage lesions, were chosen from the 98 'KA-like lesions'. There was clinical evidence that each regressing/regressed stage lesions was a KA, because all of these lesions had been a rapidly enlarging nodules with a central keratin plug, which had clearly flattened to become a keratotic plaque after a 'watch and wait' approach.…”

Hand Tumors

“…15,17 Current theory suggests reclassification of keratoacanthomas as either premalignant lesions or, furthermore, as a subtype of squamous cell carcinoma. [16][17][18][19] Conservative treatment modalities such as 5-fluorouracil, imiquimod, and intralesional methotrexate are considered second-line therapies, and early surgical excision is recommended. 15,17 …”

Skin cancer for dental professionals

“…27 The UK distribution is fairly even although it occurs more in the south west of England. The age distribution is younger than for other skin cancers.…”

“…27 Due to diagnostic difficulties these are often excised in the same way as other SCCs ■ Bowens disease -an uncommon in situ SCC, presenting as an irregular welldemarcated erythematous scaly keratotic plaque on sun-exposed skin, which is generally asymptomatic ■ Seborrhoiec keratosis ■ Atopic dermatitis ■ Atypical fibroxanthoma ■ Congenital skin tumours, for example, dermoid/dermolipoma ■ Chemical burns ■ Contact dermatitis ■ Pyoderma gangrenosum ■ BCC.…”

“…Incidence increases steadily with age, with a female predominance below age Twenty-two percent of lesions in males occur in the head and neck area, compared to 14% in females. 27 Pathology and risk factors MM is a malignant neoplasm of melanocytes that can arise within a pre-existing benign melanotic lesion or de novo from apparently normal skin. It tends to invade locally and metastasise, and can occur at any skin site, or the oral, genital, ocular or urinary epithelial surfaces.…”