72 yrs old male axillary 4 cm firm nodule was biopsied with suspition of lymphoma.

HISTO: Perifollicular epithelioid interstitial and confluent ("targetoid") atypical "histioid" infiltration with lobated/wrincled (but not grooved nuclei with eo nucleoli) with the smaller dermatopathic lymphadenopathy areas enreached with Langerhans cells.

IH (Langerin is absent there, sorry):  Histiocytic population: S100(+++)(citopl. r-ja) 100%, CD68(-), Ki67 ~30% (++), CD1a(-)(LC dermatopatic zones +), CD20(-), CD3(-)(intratumoral T lymphos +), PanCK(-), CD30(-), ALK1(-), Melan A/HMB45(-), CD23/CD21(-), CD4(-)(LC dermatopatic zones +), EMA(-), HLA DR(++) 100%, CD45RO/MPO(-), CD15(-), LCA(-), CD34(-). TdT+ infiltration absent. Multiple intertumoral CD138+ polytypic plasmacytes present.

PROPOSALS FOR DISCUSSION:

1. Langerhans cell histiocytosis/tumor/sarcoma: S100+; CD68(-); CD1a(-); CD4(-); CD23/CD21(-); HLA DR+; LCA(-); CD10+/-; Ki67 ~30% (++)?

2. Interdigitating cell tumor/sarcoma (epithelioid): S100+; CD68(-); CD1a(-); CD4(-);CD23/CD21(-); HLA DR+; LCA(-); CD10+/-; Ki67 ~30% (++)?

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