Figure 3: Immunohistological features of folliculotropic mycosis
fungoides.
(A-B) Superficial and deep dense dermal monotonous lymphocytic
infiltrate with predominantly perifollicular/folliculocenteric
distribution extending down into the mid-dermis. There is tagging of the
lymphocyte along the basal layer of the follicular epithelium, with some
lymphocytes enclosed within haloes. There is the attenuation of the
epidermis, but there is no atypia or epidermotropism, Pautrier
microabscess formation., tagging, haloed lymphocytes, lymphocyte atypia,
or pagetoid spread in the spinous layer. The interfollicular epidermis
is not involved. (hematoxylin-eosin stain, original magnification,
A:x20, and B:x40).
(C-D) Exocytosis of small to medium-sized hyperchromatic lymphocytes
into the follicular epithelium of the bulbar and isthmic portions of the
hair follicle with disproportionate spongiosis and destruction of the
hair follicles. The follicular epithelium is focally spongiotic
(hematoxylin-eosin stain, original magnification, C-D: x400).
(E-F) A close-up examination of PAS/Alcian blue stained sections reveals
mucin deposition in the hair follicles and the interstitial spaces
(PAS/Alcian blue, original magnification, E-F: x400)
(G-H) Dense CD4 positive perifollicular lymphoid aggregates with marked
infiltration of the follicular epithelium (folliculotropism) by small to
medium-sized T- T-lymphocytes (original magnification, E: x20, and
F:x400).
(I): Minimal CD8-positive T- T-lymphocytes are seen. The shift of the
CD4 positive folliculotropic T-cells (H) to the CD8 (I) ratio favors the
diagnosis of F-MF (original magnification, I:x400). The lack of
epidermotropism should not deter dermatopathologists from considering
F-MF as a diagnostic possibility.