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A 6-month-old male baby presented with a solitary skin nodule (2.5×2.5×2.5 cm) on his left cheek (figure 1). The nodule was medium-hard and sharply demarcated. The skin on the surface of the nodule was smooth. Two months earlier, the lesion was discovered coincidentally as a soybean-sized papule with no redness, swelling, heat, pain, pruritus or desquamation. The lesion then gradually increased in size and became erythematous. The infant had no systemic findings of fever, chills, night sweats or weight loss. Lymphadenopathy and hepatosplenomegaly were absent.
The key clinical feature of the case is an enlarging solitary skin nodule on his left cheek, with no other discomfort or systemic involvement. The differential diagnosis includes skin malignancy, juvenile xanthogranuloma, mastocytosis, angioma, dermatofibroma and Langerhans cell histiocytosis. Surgical resection of the entire nodule was performed for pathological diagnosis and management strategy.
Microscopically, H&E staining revealed a dense non-epitheliotropic infiltrate of small-to-medium-sized atypical T-cells. The infiltrate showed a nodular pattern in the dermis and subcutis. Immunohistochemistry showed neoplastic cells were CD3+/CD4+/CD2+/CD5+ and CD8 (−)/CD30 (−)/CD56 (−)/TIA-1 (−)/CD20 (−)/CD7 (−). The proliferative marker, Ki-67, showed a low nuclear reaction involving 10% neoplastic cells (figure 2). In situ hybridisation for Epstein-Barr virus (EBV) was negative. Clonal TCR gene rearrangements were detected (figure 3). The diagnosis of primary cutaneous …