Spontaneous regression of subungual keratoacanthoma with reossification of underlying distal lytic phalynx

A 45-year-old man presented with a rapidly enlarging keratotic lesion of the distal subungual right middle finger. An X-ray of the digit revealed a well-defined cup-shaped lytic lesion of the phalynx underlying the subungual nodule. The lesion resolved spontaneously with reossification of the underlying bony defect. The clinical history and X-ray is consistent with a diagnosis of spontaneously resolving subungual keratoacanthoma.

Keratoacanthoma: A Clinico-Pathologic Enigma

BACKGROUND

Keratoacanthoma (KA) is an extraordinary entity. Once considered a benign neoplasm that resembled a highly malignant one (pseudomalignancy), it is now viewed in an opposite light as a cancer that resembles a benign neoplasm (pseudobenignity).

OBJECTIVE

The goal was to delineate the malignant potential of this neoplasm based on the author's experience and a review of recent data and research and to emphasize the KA as a possible part of an autosomal dominant familial cancer syndrome, the Muir-Torre syndrome.

METHODS

This is a review of the literature.

RESULTS

In this work, the KA is reviewed with recent advances emphasized.

CONCLUSION

KA is an abortive malignancy that rarely progresses into an invasive SCC. The KA may serve as a marker for the important autosomal dominant familial cancer syndrome, the Muir-Torre syndrome, as a result of a defective DNA mismatch repair gene.

Generalized eruptive keratoacanthoma of Grzybowski: follow-up of the original description and 50-year retrospect

We report a follow-up of the original case of eruptive multiple keratoacanthoma (KA) described by Grzybowski in 1950 which did not show malignant transformation within 16 years after the onset of the disease in spite of a very widespread cutaneous involvement. There was no associated internal malignancy or any systemic disease either, and the patient died of a myocardial infarction unrelated to his cutaneous disorder. This case followed up for such a long time provides further confirmation that this variety of KA does not show invasive growth and usually does not progress into squamous cell carcinoma.

A case of Grzybowski's generalized eruptive keratoacanthomas

We report a case of Grzybowski's generalized eruptive keratoacanthoma which demonstrates the characteristic features of this rare condition. The recurring nature of the eruption each summer supports the suggestion that UV irradiation may act as a precipitating factor in eruptive keratoacanthoma.

Non-immunologic enhancement and regression of self-healing squamous cell carcinoma (keratoacanthoma)--ground substance and inflammation

Keratoacanthomas have many characteristics of squamous cell carcinoma and in the past were interpreted as squamous cell carcinomas. It is now known that these lesions spontaneously resolve if left untreated. In man the lesions occur on sunlight damaged areas or areas exposed to tar. Many of the experimental cancers of animals produced by topical carcinogens are keratoacanthomas. Ultraviolet light and tar are known to damage fibroblast and ground substance viscosity. It has recently been proposed that anything that decreases ground substance viscosity would encourage the spread of tumors, by weakening tissue resistance. The rapidly growing keratoacanthoma produces invasive pressure and moves into deeper, less damaged dermis. An inflammatory reaction occurs in the depth of the lesion and a very characteristic granulocytic response occurs. Granulocytes release connective tissue active peptides which stimulate fibroblast and ground substance formation. The fibroblast proliferation is followed by fibrosis and the shrinking and disappearance of the tumor. The characteristic pustule that spurts granulocytes into the depth of the tumor has been experimentally blocked by hyaluronidase and other substances that damage ground substance viscosity. Edema is essential to produce this inflammatory reaction. However, this inflammatory phenomenon occurs vigorously in keratoacanthoma. It is proposed that a keratoacanthoma is a tumor that does not produce hyaluronidase or other substances that decrease ground substance viscosity. It is a deviant cell that can only move through areas of decreased ground substance viscosity. When it reaches tissues of normal viscosity edema and an inflammatory reaction occurs.(ABSTRACT TRUNCATED AT 250 WORDS)

Regression of induced keratoacanthomas in anagen (hair growth phase) skin grafts in mice

Transplants of experimental keratoacanthomas induced in skin grafts which were in the growth phase of the hair follicle cycle (anagen phase) were carried out in immunocompetent and immunoincompetent receipients ("nude" mouse, nu/nu). No differences in gross graft observations were noticed. More than 80% of all keratoacanthomas disappeared postgrafting. This percentage was the same for both groups of recipients. These data are in keeping with a nonimmunological regression of experimental keratoacanthomas. A possible correlation with the hair follicle cycle is suggested.

Giant keratoacanthoma of the plantar foot: a report of two cases

KA develops from a rapidly growing, firm, smooth nodule into a mature dome-shaped lesion with a central core filled with keratin that usually degenerates into an involuting keratinous mass. KAs must be differentiated from squamous cell carcinoma. Classically, KA is a benign tumor that is self-limiting. However, there is controversy concerning the aggressiveness of the tumor. Some authors believe there is no way to determine the aggressiveness of the tumors and they should be classified as low grade squamous cell carcinomas (3). Others feel that the risk of malignant transformation is not a serious consideration but misdiagnosis is, due to the histopathologic similarities (31, 33). Overall, the literature shows that solitary and giant lesions should be excised. Excisional biopsy yields a more cosmetic scar and increases the chance for an accurate biopsy diagnosis. Multiple and multinodular lesions should be excised if they have the potential for causing a mutilating deformity but are otherwise treated systematically. If a solitary or multiple lesion which is left to spontaneously resolve shows signs of aggressiveness, even with a biopsy indicating that it is a KA, it should be immediately excised. Solitary and giant KA are usually not considered to be located on the palms and soles. However, with the cases presented here, there are now a total of 4 cases in the literature. Therefore, KA should be included in the differential diagnosis when dealing with rapidly growing tumors on the plantar aspect of the foot.