Unmasking a T cell lymphoma: Folliculotropic mycosis fungoides with a gamma-delta phenotype

Gamma/Delta (γδ) T Cells: The Role of the T-Cell Receptor in Diagnosis and Prognosis of Hematologic Malignancies

ABSTRACT

There are 2 types of T cells: αβ and γδ T cells, named based on the composition of the T-cell receptor. γδ T cells are rare, making up 0.5%-10% of T cells. Although most leukemias, lymphomas, and immune-mediated conditions derive from αβ T cells, a handful of rare but important diseases are generally derived from γδ T cells, particularly primary cutaneous γδ T-cell lymphoma, hepatosplenic T-cell lymphoma, and monomorphic epitheliotropic intestinal T-cell lymphoma. There are also malignancies that may evince a γδ TCR phenotype, including large granulocytic lymphocyte leukemia, T-cell acute lymphobplastic leukemia (T-ALL), and mycosis fungoides, although such cases are rare. In this article, we will review the genesis of the T-cell receptor, the role of γδ T cells, and the importance of TCR type and methods of detection and outline the evidence for prognostic significance (or lack thereof) in lymphomas of γδ T cells. We will also highlight conditions that rarely may present with a γδ TCR phenotype and assess the utility of testing for TCR type in these diseases.

The significance of epidermal involvement in primary cutaneous gamma/delta (γδ) T-cell lymphoma: A systematic review and meta-analysis

BACKGROUND

Primary cutaneous gamma/delta (γδ) T-cell lymphoma (PCGDTCL) is a rare, aggressive peripheral T-cell lymphoma. There is evidence that patients with epidermotropic PCGDTCL may have an improved prognosis compared with those with only dermal and/or subcutaneous involvement.

METHODS

Systematic review of the literature and application of inclusion criteria yielded 48 manuscripts detailing the cases of 104 patients.

RESULTS

Of the 104 patients, 57 were male (51.4%) and 47 were female (48.5%) Based on provided histopathologic descriptions, 57 cases (54.8%) had no epidermotropism, 47 cases (45.2%) patients demonstrated any degree of epidermotropism, and 25 cases were predominantly epidermotropic (25/104, 24%). Five-year overall survivals for patients with no epidermotropism, any epidermotropism, and predominantly epidermotropic presentation were 32.8%, 28.9%, and 40.0%, respectively (p = 0.40). The most commonly performed immunohistochemical markers were CD3, CD4, CD8, CD5, CD7, CD30, CD56, TCR beta, TCR γ, and TCR δ. There was no statistically significant difference in immunophenotype between groups. Lesion morphology was described in the majority of cases (85/104, 80.9%); most cases presented as a combination of nodules, plaques, and tumors (77.4%). Several cases had more atypical presentations, including "mycosis-fungoides-like" and ulcerated.

CONCLUSION

In PCGDTCL, neither epidermotropism nor predominantly epidermotropic phenotype predict a better prognosis. In addition, the case report literature in dermatology and dermatopathology is rich and highly valuable.