Histology Resembling Cutaneous T-Cell Lymphoma in Nodular Scabies: A Case Report.

Sir,

Scabies is a common parasitic infection caused by the mite Sarcoptes scabiei var hominis.[1] Herein, we report a case of nodular scabies with unusual clinical features in which the histopathological features closely resembled those of cutaneous T-cell lymphoma (CTCL).

A 69-year-old Japanese woman with a history of subarachnoid hemorrhage was referred to our department for diagnosis of eruptions that had been present for 7 months. At another hospital, T-cell lymphoma had been suspected based on histologic findings in a skin biopsy from her left upper arm. At her first visit to our department, erythematous papules and small brown nodules were seen on the left side of her chest, left axilla and left upper arm [Figure 1a]. She had no complaints of itching. The scabies tunnels were not seen on her hands and fingers. Histopathology specimens stained with hematoxylin and eosin (H and E) taken at the previous hospital showed features of CTCL without epidermal Pautrier microabscesses [Figure 1c and d]. Laboratory tests, including liver and kidney functions, were within the normal limits. The white blood cell count (9500/μl; normal range, 3400-7300/μl) and serum soluble interleukin-2 receptor level (535 U/ml; normal, 145-519 U/ml) were slightly elevated. Blood eosinophil percentage was within the normal limit and abnormal peripheral blood lymphocytes were not detected. Positron emission tomography and computed tomography showed no abnormal fluorine-18 2-fluoro-2-deoxy-D-glucose uptake in her whole body.

Figure 1

Clinical photographs (a, b) and results from histological studies (c-e). (a) At the first visit, erythematous papules and small brown nodules were seen on the left side of the chest, left axilla and left upper arm. (b) At 4 weeks after completion of treatment, all eruptions had faded and post-inflammatory hyperpigmentation was seen. (c) A dense nodular infiltration of hematoxylin-stained cells was present in the whole dermis (H and E, ×40). (d) Large convoluted lymphocytes showing a clear perinuclear halo predominated in the infiltrate and small numbers of eosinophils were also present (H and E, ×400). (e) In a specimen stained with CD4, a mite was detected within the stratum corneum of the epidermis (original magnification, ×100)

We considered the disease to be possible CTCL. A punch biopsy was performed from a nodule on her left upper arm to obtain the immunohistochemical profile for final diagnosis. HE staining showed similar findings in the previous hospital. Immunohistochemically, the infiltrating cells were positive for CD3 and CD4 [Figure 1e]. Intermediate numbers of CD8-positive cells and small numbers of CD20-positive cells were also seen. In a specimen stained with CD4, a mite was detected within the stratum corneum of the epidermis [Figure 1e]. At her second visit to our department, scabies was diagnosed based on analysis of the nodules in a potassium hydroxide (KOH) test. Oral administration of ivermectin (Maruho Co., Osaka, Japan) (9 mg, 2 times, 2 weeks apart) was started. After 4 weeks, all eruptions disappeared and only hyperpigmentation remained [Figure 1b].

Classically, scabies affects several skin sites, predominantly the hands between the fingers, wrists, shoulders and genital area.[2] However, the lesions in our case were limited to the left side of the chest, left axilla and left upper arm, without scabies tunnels on the hands or a subjective symptom of itching. These unusual clinical features and the histopathological findings at another hospital did not suggest scabies as a differential diagnosis. Fortunately, we obtained a clue for the diagnosis due to thin sectioning of slice preparations for immunohistochemistry. The histological findings of a nodular form of scabies showed similarity with malignant lymphoma.[34] This case illustrates the importance of medical practitioners paying attention to cases with unusual clinical features of scabies and shows that a KOH test is required at the first physical examination.