Density of neoplastic lymphoid infiltrate, CD8+ T cells, and CD1a+ dendritic cells in mycosis fungoides

Abstract

Background/aims: CD8+ T cells and epidermal/dermal dendritic cells expressing CD1a are found among neoplastic CD4+ T cells in mycosis fungoides (MF) lesions. This study analysed the relation of CD8+ tumour infiltrating lymphocytes (TILs), CD1a+ epidermal Langerhan's cells (LCs), and dermal dendritic cells (DDCs) to clinicopathological parameters in 46 MF cases.

Methods: Pretreatment diagnostic biopsy specimens of 46 MF cases were submitted to histological analysis and immunohistochemistry. Four histological grades were defined based on the density of the neoplastic infiltrate: grade 1 (mild superficial perivascular infiltrate), grade 2 (moderate superficial perivascular infiltrate with some tendency to confluence), grade 3 (pronounced superficial band-like infiltrate), and grade 4 (deep nodular infiltrate). Epidermotropism was scored as low, moderate, or high. Numbers of CD8+ T cells and of dermal and epidermal CD1a+ cells were scored as 1 (low), 2 (moderate), and 3 (high). Correlations between these parameters and clinical data (age, sex, clinical type of lesions, stage, response to treatment, and recurrence) were analysed by the chi(2) test.

Results: Numbers of TILs and DDCs were associated with subepidermal infiltrates, being lower in less dense infiltrates, whereas there was no association between epidermal CD1a+ cells and the analysed parameters. Complete remission in treated patients was related to subepidermal infiltrates but not to TILs, LCs, or DDCs.

Conclusions: These results support the notion that CD8+ cells and dermal CD1a+ cells are active against tumour cells. MF with low numbers of TILs could represent an early stage of the disease, before TILs are activated against tumour specific antigens.

Figure 1

Type of subepidermal lymphoid infiltrate and density of CD8+ and CD1a+ cells in mycosis fungoides. (A,D) Microphotographs taken from two cases with different densities of neoplastic infiltrate and grades of epidermotropism: (A) mild lymphoid infiltrate, superficial, and with mild exocytosis and no tendency to confluence (infiltrate density and epidermotropism grades 1); (D) band-like subepidermal lymphoid infiltrate associated with more than three Pautrier’s microabscesses, one included in this field (infiltrate density and epidermotropism grades 3). (B,E) Immunostaining with anti-CD8 monoclonal antibody in two cases on frozen sections: (B) there are few and isolated dermal reactive lymphocytes in a case with dermal infiltrate grade 1 (CD8 positivity score 1); (E) CD8+ cells are numerous and form small groups in a case with dermal infiltrate grade 3 (CD8 positivity score 3). (C,F) Immunostaining with anti-CD1a monoclonal antibody in two cases on paraffin wax embedded sections: (C) there are few epidermal Langerhan’s cells and dermal dendritic cells, with no tendency to form small groups in a case with dermal infiltrate grade 1 (epidermal and dermal CD1a positivity score 1); (F) there are many Langerhan’s cells in all the epidermal layers with a tendency to cluster (epidermal CD1a positivity score 2), whereas the dermal dendritic cells are particularly numerous and form large aggregates (dermal CD1a positivity score 3): the case shows a dermal infiltrate grade 3.

Figure 2

Distribution of CD8 positivity scores in the four groups with different grades of subepidermal lymphoid infiltrate.

Figure 3

Distribution of dermal CD1a positivity scores in the four groups with different grades of subepidermal lymphoid infiltrate.