PMC4734960_01
(A) An ill-defined, 1.2-cm, round, erythematous subcutaneous nodule on the left flank. (B) The ill-defined tumor is mainly located in the dermis and subcutis. The margin of the tumor is marked by arrowheads.
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A 29-year-old female patient presented with a 1.2-cm, ill-defined, erythematous subcutaneous nodule on the left flank (Fig. 1A), which appeared a month ago and increased in size over time. Microscopically, the lesion showed poorly circumscribed infiltrates of tumor cells forming mostly solid sheets in the dermis and subcutis (Fig. 1B).
(A) There is patchy infiltration by aggregates of the tumor cells. Tumor cells are usually monotonous and have indistinct cell borders. Clusters of lymphocytes are admixed with tumor cells in focal areas without eosinophils. (B) The constituent cells have ovoid cell morphology with abundant eosinophilic cytoplasm. (C) Their nuclei are oval and sometimes indented. Nuclear grooves are frequently seen. Although occasional enlarged nuclei are identified, mitoses are rarely seen. (D) There is no epidermal involvement.
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Eosinophils were notably absent (Fig. 2A). They had moderately abundant and lightly eosinophilic cytoplasm (Fig. 2B). Characteristically, there was no epidermal involvement by tumor cells (Fig. 2D).
The neoplastic cells diffusely express CD1a (A) and S100 protein (B). (C) Langerin (CD207) is typically negative. (D) No Birbeck granules are seen on transmission electron microscopy (x8,000).
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The neoplastic cells in the tumor were diffusely immunopositive for S100 and CD1a (Fig. 3A, B). Scattered langerin-positive bystander Langerhans cells serve as internal positive controls (Fig. 3C). Despite intensive scrutiny, no Birbeck granules were identified on electron microscopy (Fig. 3D).