Does the aberrant expression of CD2 and CD25 by skin mast cells truly correlate with systemic involvement in patients presenting with mastocytosis in the skin?

BACKGROUND

Neoplastic mast cells involving the bone marrow (BMMCs) of patients with mastocytosis display an aberrant expression of CD25 and/or CD2 antigens. The aim of this study was to determine the frequency of CD2 and CD25 expression on skin mast cells (sMCs) of patients with mastocytosis in the skin at the early stage of the disease. Furthermore, the usefulness of the phenotypic profile of sMCs for the diagnosis of systemic mastocytosis (SM) was evaluated.

METHODS

The 52 adults included in the study were diagnosed with mastocytosis strictly according to the criteria of the World Health Organization. CD117, CD2 and CD25 antigen expression on sMCs was detected by immunohistochemistry. The presence of the KIT D816V mutation in the BM was analyzed using allele-specific PCR.

RESULTS

The presence of CD2- or CD25-positive sMCs was detected in 57.1% of cutaneous mastocytosis (CM) and 90.3% of SM cases (p = 0.008). In all mastocytosis patients, CD2 expression on sMCs was more frequent than CD25 expression (67.3 and 38.5%, respectively). Moreover, CD2 expression on sMCs was more frequent in SM than in CM cases (p = 0.02). The presence of one of the aberrant sMC antigens was detected in 84.2% of patients with the KIT D816V mutation in the BM. A positive correlation between densities of CD25- and CD117-positive sMCs was found in SM patients (r = 0.46, p = 0.009).

CONCLUSIONS

Although sMCs displayed immunoreactivity for one of the neoplastic antigens in the majority of SM patients, the aberrant CD2 and/or CD25 expression on sMCs is not as indicative of SM as the BMMC immunophenotype.