title: Cytokeratin-positive interstitial cell neoplasm: a case report and classification issues.
abstract: OBJECTIVE
  Tumours of dendritic/accessory cell origin are rare neoplasms arising in lymph nodes. Among these, tumours derived from cytokeratin-positive interstitial reticulum cells (CIRCs), a subset of fibroblastic reticulum cells, are reported even less frequently. The International Lymphoma Study Group (ILSG) has recently proposed a classification for tumours of histiocytes and accessory dendritic cells in which CIRC tumours are not included. We report a case of a CIRC tumour arising in a submandibular lymph node of a 66-year-old male.
  
  
  RESULTS
  The neoplasm was composed of spindle cells with elongated or round nuclei, prominent nucleoli and abundant cytoplasm. These cells were arranged in a diffuse fascicular and vaguely whorled pattern. The tumour cells stained diffusely for S100, vimentin, desmin, lysozyme, and focally for CD68 and cytokeratins 7, 8, 18, CK-AE1 and CK-pool. Electron microscopy was performed for further evaluation on samples taken from the paraffin block; this revealed cytoplasmic projections and rudimentary cell junctions.
  
  
  CONCLUSIONS
  Histopathologist should be aware of the existence of tumours deriving from CIRCs, as these cases may be misdiagnosed as metastatic carcinoma. Careful clinical and pathological evaluation is necessary to exclude this possibility.
authors.affiliation: Department of Human Pathology and Oncology, Siena University, Siena, Italy.
authors.forename: K
authors.initials: K
authors.lastname: Schuerfeld
authors.forename: S
authors.initials: S
authors.lastname: Lazzi
authors.forename: M M
authors.initials: MM
authors.lastname: De Santi
authors.forename: A
authors.initials: A
authors.lastname: Gozzetti
authors.forename: L
authors.initials: L
authors.lastname: Leoncini
authors.forename: S A
authors.initials: SA
authors.lastname: Pileri
mesh_terms: D000368:Aged; D003713:Dendritic Cells / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology*; D003937:Diagnosis, Differential; D006801:Humans; D007633:Keratins / Q000378:metabolism*; D008198:Lymph Nodes / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D008223:Lymphoma / Q000145:classification / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008854:Microscopy, Electron; D013365:Submandibular Gland Neoplasms / Q000145:classification / Q000378:metabolism / Q000473:pathology*; D014463:Ultrasonography
chemical_list: D007633:Keratins