Analysis of histopathologic and electron microscopic determinants of keratoacanthoma and squamous cell carcinoma

Abstract

Histopathologic study of 108 keratoacanthomas and 14 squamous cell carcinomas failed to reveal any consistent, single feature allowing for their distinction. Variation in clinical features of keratoacanthoma minimizes their value in this regard. On the other hand, crater, flask‐like configuration, lipping of edges, collarette and cytoplasmic eosinophilia were statistically more frequent in lesions regarded as keratoacanthoma whereas atypical cytologic alterations including greater numbers of typical and atypical mitoses and a desmoplastic tumor stroma were most frequent in squamous cell carcinoma. Electron microscopy of examples of each lesion revealed the well‐differentiated appearance of cells comprising keratoacanthoma. In addition, intracytoplasmic aggregates of desmosomes were unique but not consistently observed in keratoacanthoma. Cells comprising squamous cell carcinoma exhibited decreased numbers of tonofilaments and intercellular desmosomes. The subjective nature of these distinguishing ultrastructural features minimizes the value of electron microscopy for the differentiation of these two lesions. Intranuclear bodies noted in some cells of keratoacanthoma resemble similar non‐viral particles observed in a variety of pathologic and even some normal cells. Interpretation of these findings as well as follow‐up observations have provided practical guidelines for therapy.

Immunohistochemical staining for desmogleins 1 and 2 in keratinocytic neoplasms with squamous phenotype: actinic keratosis, keratoacanthoma and squamous cell carcinoma of the skin

“…The Dsg staining that we have found appears consistent with the results of electron microscopical studies in KAs, in which the numbers and cell-surface densities of desmosomes have been found to be normal whereas in SCCs they are reduced (Fisher et al, 1972;Miracco et al, 1992). We are not aware of any ultrastructural studies of desmosomes in AKs.…”

“…We have examined the staining for Dsg using the monoclonal antibody 33-3D, a mouse IgM monoclonal antibody, that recognizes the cytoplasmic domains of human Dsgl and Dsg2 and can be used on frozen sections (Vilela et al, 1995; DR Garrod, unpublished observations (Fisher et al, 1972;Janecka et al, 1978;Schwartz, 1994;Schwartz, 1996).…”

Diagnosis and Follow-Up of Keratoacanthoma-Like Lesions: Clinical-Histologic Study of 43 Cases

“…Histopathologic diagnosis was rendered as KA, SCC, or undetermined. Elastic fibers were not evaluated because, despite the fact that it has been demonstrated that the presence of intraepithelial elastic fibers favors the diagnosis of KA, [8][9][10][11][12][13][14][15] this finding is not reliable for differentiating between the two tumors. 4 Initially, the variables were evaluated descriptively.…”

Intercellular junctions of methylcholanthrene-induced rat skin basocellular and squamous carcinomas

“…In relatively well differentiated areas of human tumours they found several gap junctions, but none in poorly differentiated areas. The numerical decrease of desmosomes and appearance of desmosome-free cytoplasmic processes has been described not only in squamous tumours, but also in pre-malignant lesions of the epithelium (Klingmuller et al, 1970;Fisher et al, 1972;Sugar, 1972;Lever & Schaumburg-Lever, 1975;Schindler et al, 1982). In the developing invasive character of tumours, McNutt (1976) suggested that the decreased number of hemidesmosomes may play a significant role.…”