Keratoacanthomas and lymphomatoid papulosis.

Abstract

To the Editor: Kato and Matsue reported a case of follicular lymphomatoid papulosis (LyP) with striking similarity to the histologic features of a keratoacanthoma (1). We are reporting a patient with classic lesions of LyP and multiple keratoacanthomas. The keratoacanthomas were infiltrated by atypical lymphocytes, similar to the ones seen in the LyP lesions. CASE REPORT A 67-year-old woman presented with a ten-year history of recurrent erythematous papules and nodules involving the upper and lower extremities. The lesions were asymptomatic, resolving in 6 to 8 weeks with some residual scarring. During the two years prior to presentation, a few painful nodules and plaques with a central keratotic dell had developed on her left leg (Fig. 1). The patient had not received treatment for LyP and had no history of lymphoma or Hodgkin's disease.FIG. 1Histopathologic examination of the small papules showed a dense dermal infiltrate composed of large and pleomorphic lymphocytes with abundant vacuolated cytoplasm and prominent nucleoli admixed with small and intermediate lymphocytes with irregular nuclear contour and hyperchromasia (Fig. 2). Numerous mitoses and scattered neutrophils were also noted. Biopsy of one of the large keratotic nodules showed a large endophytic nodule with a central keratotic crater (Fig. 3). The lobule was composed of broad interconnected sheets and strands composed of large squamous cells with abundant glassy cytoplasm without significant nuclear atypia (Fig. 4). The surrounding stroma showed edema, telangiectasia, and a mixture of neutrophils and highly pleomorphic lymphocytes (Fig. 5). The atypical lymphocytes from both lesions were CD3 positive with CD30 expression on the large cells.FIG. 2: Low power view of a LyP lesion. A dense atypical lymphoid infiltrate is noted involving the entire dermis.FIG. 3: Low power view of keratoacanthoma with a central crater filled with laminated keratin.FIG. 4: Low power view of the hyperplastic squamous epithelium surrounding the crater. The keratinocytes are large with abundant pale cytoplasm and mild nuclear atypia. A dense atypical lymphoid infiltrate is noted in the stroma.FIG. 5COMMENTS The case reported by Kato and Matsue as follicular LyP is similar to one of the cases initially reported by Pierard et al. and to our present report (1,2). In their article, a papule with a central depression exhibiting a markedly hyperplastic squamous epithelium composed of large, slightly atypical, ground-glass squamous cells is described and illustrated (1). Such histologic findings differ from the other few reports of follicular LyP, which showed the atypical lymphocytes surrounding remnants of hair follicles and follicular cysts, without the hyperplastic atypical squamous epithelium (2-7). We believe that the atypical lymphoid infiltrate noted in our case is part of the reactive inflammatory infiltrate normally seen in keratoacanthomas, rather than an unusual variant of LyP. Willemze stated that LyP most likely represents an abnormal immune response to an unidentified antigenic stimulation (8). Furthermore, Pierard et al. speculated that follicular LyP might represent a response to ruptured hair follicles and follicular cysts (2,3). We concur with the concept of LyP being a reaction to a variety of stimuli. Lymphomatoid papulosis could then be reactive in nature, yet often clonal or oligoclonal. Since our patient, like Kato's patient, had otherwise classic lesions of LyP, it is reasonable to believe that a keratoacanthoma arising from a patient with LyP is likely to have atypical lymphocytes within the reactive infiltrate. Regardless of the possible association, keratoacanthomas and LyP are both theoretically self-healing lesions. However, the uncertain biologic behavior of unresected lesions is a compelling argument for their treatment. Interestingly, our patient's residual keratotic nodules resolved with intralesional injections of methotrexate, a treatment modality applied to both keratoacanthomas and LyP (9,10). Joan Guitart, M.D. Kenneth Gordon, M.D. Department of Dermatology; Northwestern University Medical School; Chicago, Illinois