A 10-year-old boy, previously healthy, presented with a 14-day history of a right thoracic nodule, initially diagnosed as an abscess. He was treated with oral cefadroxil and topical fusidic acid. On examination, a well-demarcated, asymptomatic, erythematous-violaceous nodule was observed (Figure 1). Excisional biopsy was performed. The surgical defect during the procedure is shown in Figure 2.
Histopathological examination revealed a non-circumscribed proliferation of large cells with marked nuclear pleomorphism, prominent nucleoli, and abundant clear cytoplasm, with numerous mitotic figures (Figure 3). Immunohistochemistry showed strong and diffuse expression of CD30 in atypical cells (Figure 4), and positivity for granzyme B, CD2, CD4, and CD25 in atypical T-cells (Figure 5). Numerous intermingled histiocytes were positive for CD68 and CD163, but negative in the atypical cells (Figures 6 and 7). ALK1 was negative in lymphoid cells (Figure 8). These findings supported the diagnosis of primary cutaneous anaplastic large cell lymphoma. Laboratory and PET-CT evaluation showed no extracutaneous disease. Localized electron beam radiotherapy was performed.