title: Follicular lymphomatoid papulosis revisited: a study of 11 cases, with new histopathological findings.
abstract: BACKGROUND
  Follicular lymphomatoid papulosis (LyP) describes a variant of LyP with perifollicular infiltrates and some degree of folliculotropism of CD30(+) atypical lymphocytes. So far, only a few cases of follicular LyP have been described.
  
  
  OBJECTIVE
  Our goal was to study the clinicopathologic features of follicular LyP in a series of 11 cases (9 male, 2 female; age range 7-78 years, mean age 50 years).
  
  
  METHODS
  In all, 113 cases of LyP were reviewed to select cases showing follicular involvement. Histology was correlated with the clinical data to exclude cases of CD30(+) anaplastic large-cell lymphoma or folliculotropic mycosis fungoides.
  
  
  RESULTS
  Six cases were classified as type C and 4 as type A, whereas the remaining case manifested epidermotropism of small lymphocytes in a background of a typical type A lesion (overlapping type A/B). Perifollicular infiltrates of CD30(+) atypical lymphoid cells were seen in all 11 cases, with infiltration of the follicular epithelium in 8 cases. Hyperplasia of the follicular epithelium was observed in 4 cases; ruptured hair follicles, in 3 cases; and follicular mucinosis, in 2 cases. In addition to hair follicle infiltration, atypical cells were recognized within sebaceous glands in 2 lesions. New findings were presence of numerous intrafollicular neutrophils in 2 patients, who clinically had pustules in addition to papules. Other histopathological features encountered included perieccrine infiltration (n = 5), focal subcutaneous involvement (n = 4), granulomatous inflammation (n = 3), epidermal hyperplasia (n = 2), and 1 each of infiltration of muscle bundles, numerous eosinophils in the infiltrate, and angiocentricity.
  
  
  CONCLUSIONS
  This was a retrospective study.
  
  
  CONCLUSIONS
  Follicular LyP is a variant of LyP with involvement of hair follicles, mostly in the form of perifollicular infiltrate with variable degree of folliculotropism. Other changes including hyperplasia of the follicular epithelium, rupture of hair follicle, and follicular mucinosis are less common. Rarely, intrafollicular pustules can be seen in the follicular epithelium; such lesions manifest clinically as pustules.
authors: Kempf und Pfaltz, Histologische Diagnostik, Zürich, Switzerland. kempf@kempf-pfaltz.ch
authors: Werner
authors: W
authors: Kempf
authors: Dmitry V
authors: DV
authors: Kazakov
authors: Hans-Peter
authors: HP
authors: Baumgartner
authors: Heinz
authors: H
authors: Kutzner
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001706:Biopsy; D002648:Child; D003872:Dermatitis / Q000473:pathology; D005260:Female; D018859:Hair Follicle / Q000473:pathology*; D006801:Humans; D008214:Lymphocytes / Q000473:pathology; D017731:Lymphomatoid Papulosis / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D000507:Mucinosis, Follicular / Q000473:pathology*; D012189:Retrospective Studies; D012878:Skin Neoplasms / Q000473:pathology*; D055815:Young Adult