Recurrent keratoacanthomas developing after spontaneous resolution

Squamous Cell Carcinoma With Unusual Benign-Appearing Cystic Features on Histology

Squamous cell carcinoma (SCC) is a malignancy that arises from keratinocytes of the epidermis. Cystic variants of several types of cutaneous neoplasms have been rarely described in the literature. We report a case of biopsy-proven, well-differentiated invasive SCC treated with Mohs surgery. On frozen sections, the pathology slides showed benign-appearing cystic structures in the margins that persisted after it had appeared that the original malignancy had been cleared. After taking another Mohs stage due to clinical suspicion, additional SCC was found and was subsequently cleared after two more Mohs stages. To the best of our knowledge, this is the first report to histologically demonstrate biopsy-proven invasive SCC with benign-appearing cystic structures on frozen sections.

Efficacy of oral retinoids for keratoacanthoma centrifugum marginatum

Keratoacanthoma centrifugum marginatum (KCM) is a rare variant of keratoacanthoma. This condition is difficult to diagnose because of its large size and expansive nature and may be diagnosed as a malignant tumor. There are various treatments such as surgery and oral retinoids; however, limited studies have verified their effectiveness. Here, we report a case of KCM on the anterior chest of a 50-year-old woman and evaluate the efficacy of oral retinoids. In this case, oral retinoids were highly effective for KCM treatment. A total of 55 cases of KCM, including 54 previously reported cases, were reviewed, and their clinical characteristics and treatment were examined. In this report, 14 of 16 patients were effectively treated with oral retinoids, resulting in a treatment rate of 87.5%. Furthermore, even low-to-medium doses were sufficient for treatment and prevention. KCM can be misdiagnosed as a malignant disease based on its clinical features. Due to its large size and expansive nature, a wide excision may be performed; however, because oral retinoids have a very high response rate, an accurate diagnosis will help avoid an unnecessary wide excision.

Keratoacanthoma of the lip: A case report with emphasis on histogenesis

Keratoacanthoma (KA) is a benign epithelial tumor which presents clinically as a proliferating dome-shaped keratin-filled crater. The lesion occurs predominantly upon sun-exposed areas of the body and is known to arise from hair follicle. Actinic rays are a major contributing factor in the etiology. It simulates grossly as well as microscopically a low-grade squamous cell carcinoma. KAs occur habitually on the mucous membrane as well, but their origin in these cases is debatable, owing to the lack of hair follicles in these sites. Our report is an attempt to demonstrate the cells that could be responsible for initiation of this lesion on the oral mucosa.

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

BACKGROUND

Although the precise etiology of keratoacanthoma (KA) is unknown, KA is generally assumed to differentiate toward hair follicles based on previous studies of experimental carcinogenesis.

METHODS

We performed a comprehensive immunohistochemical study of various follicular markers in all stages of KA. A total of 67 tumors, including 16 early or proliferative stage lesions, 43 well-developed stage lesions, five regressing stage lesions and three regressed stage lesions, were subjected to the analysis.

RESULTS

CK15 (clone C8/144B), CK19 and CD34 were not expressed at any stage. CK1, CK10, CK16, CK17, CK15 (clone LHK15) and calretinin showed dynamic changes in their expression in KA depending on the stage.

CONCLUSIONS

KA is a follicular neoplasm with infundibular/isthmic (upper segmental region of hair follicles) differentiation. It is considered that early or proliferative stage tumors show keratin-filled invaginations with infundibular differentiation and gradual isthmic differentiation. Well-developed examples of KA generally show isthmic differentiation in the whole lesions. The regressed stage KAs lose the features of this type of follicular differentiation and show epidermal characteristics. No expression of CK15 (clone C8/144B) was observed in KAs, although this finding is insufficient to completely rule out the correlation between the regression of KA and the hair follicle cycle.