Clinical history: A 13-year-old boy presented a painless left cervical adenopathy, increased fatigue, loss of appetite, occasional mild night sweats and a 30-pound weight loss for five months. CT imaging study of the chest, abdomen and pelvis showed multiple enlarged lymph nodes with largest measuring 4.5 cm in the left neck, mediastinum, left hilum, epigastrium, splenic hilum, and peripancreatic areas. Multiple splenic lesions (largest 3.1 cm) were also identified. Liver was unremarkable. An excisional biopsy of left supraclavicular lymph node was performed.

Gross examination: The excised specimen consisted of two portions of red-tan soft tissue, measuring 2.5 cm and 0.8 cm at greatest dimension.

Microscopic examination and immunohistochemistry: 

 An excisional biopsy of enlarged left supraclavicular lymph node showed extensive nodal architectural effacement by a nodular proliferation containing scattered large atypical mononucleated, binucleated and multinucleated cells with prominent eosinophilic nucleoli in the background of eosinophils, small lymphocytes, and plasma cells. The large atypical cells were positive for PAX-5 (weak), CD30 and CD15 (partial), and negative for CD3, CD20, CD45RB, and ALK-1 by immunohistochemical stains (Fig.1A to C).

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Fig 1a. CHL_40x

Fig 1a. CHL_40x

Fig 1b. CD30 x40

Fig 1b. CD30 x40

Fig 1c. CD15 x40

In addition, there were multiple distinct sheets of large cells with nuclear grooves and abundant eosinophilic cytoplasm, which were positive for CD43, CD1a, S-100, and langerin, confirming them to be Langerhans cells (Fig.1D to F). Repeated next-generation sequencing of microdissected Langerhans cells identified the BRAF V600E mutation with an allele frequency of 2% to 4%, whereas no MAP2K1 hotspot mutations were identified.

Fig 1d. 40x

Fig 1d. 40x

Fig 1e. CD1a x40

Fig 1 f. Langerin x40

Fig 1 f. Langerin x40