Large cell acanthoma manifesting as multiple white papules on extremities

[Anatomoclinical study of large-cell acanthoma]

BACKGROUND

Large-cell acanthoma (LCA) is a benign tumour initially described in 1970, since when it has been subject to controversy and remains poorly understood. We carried out a single-centre anatomoclinical study in order to identify the clinical and histological characteristics of the disease.

PATIENTS AND METHODS

Slides classed as LCA in our cutaneous histopathology laboratory were re-read and subjected to Melan-A and HMB45 immunohistochemical labelling. Diagnosis was based upon the presence of a clearly delineated epidermal lesion comprising keratinocytes twice as large as cells adjacent to the lesion. Clinical information was obtained through the analysis of existing requests and clinical files.

RESULTS

We identified 20 cases of LCA. Mean patient age was 70 years and the sex ratio was 0.25. The mean disease duration was 1.6 years. In most cases, a pigmented macule or papule was seen, sometimes with a verrucous surface. LCA had not been diagnosed by the clinician in any of the cases seen. In terms of histology, all lesions were clearly delineated, with hypergranulosis beneath hyperorthokeratosis, occasionally with accentuation of the papillary outline. An accentuated stratum lucidum was noted in 80% of cases. In the pigmented forms, immunohistochemical labelling showed no increase in melanocyte count.

DISCUSSION

LCA is a benign lesion that is most likely underdiagnosed since it is poorly known to clinicians and to certain pathologists. It is seen primarily in adult women and is found on the limbs and on the face. Some debate surrounds the definition of LCA as a separate entity, and some authors assimilate it with solar lentigo, but this hypothesis is countered by the existence of hypopigmented forms and we consider it to be a specific anatomoclinical entity.