SPTCL is a rare T-cell lymphoma recognized by the new World Health Organization (WHO)-European Organization for Research and Treatment of Cancer (EORTC) classification for cutaneous lymphomas.[2
] Lymphomas expressing TCR - αβ which is normally CD8 + and CD56 –, are restricted to the subcutaneous tissue and often run an indolent course. In contrast, cases with TCR γδ are CD4 –, CD8 – and CD56 + and may involve the epidermis and have a poor prognosis.[2
] On this basis, according to the WHO-EORTC classification, SPTCL is restricted to cases with αβ TCR and those with TCR γδ are placed in a new category of primary cutaneous peripheral T cell lymphomas—cutaneous γ T-cell lymphoma.[2
Each T cell is genetically programmed to recognize a specific cell-bound antigen by means of an antigen-specific T cell receptor. In approximately 95% of T cells, the TCR consists of a disulfide-linked heterodimer made up of an a and α β polypeptide chain, each having a variable and a constant region. In a minority of T cells, another type of TCR, composed of, γ and δ polypeptide chains is found. TCR diversity is generated by somatic rearrangement of the genes that encode the α, β, γ, and δ TCR chains.[5
There are various reasons for missing a histopathologybased diagnosis. In the early stages of SPTCL, the infiltrate may lack significant atypia, and the classical histopathology may not be evident later when the lesions are regressing.[4
] In our case, the diagnosis may have been initially missed because of the lack of familiarity of the general pathologist, who reported the first biopsy, with SPTCL.
Another important finding with our patient was that she was CD56 –. SPTCL patients who are CD56 – have been reported to have a better prognosis[2
] due to which we went ahead with a very nonaggressive line of management.
According to the earlier classification, SPTCL was considered to be a very aggressive disease with a poor prognosis. This was because both tumors with TCR αβ as well as those with TCR γ were classified together as a single entity. Currently, tumors with TCR γδ are classified separately and SPTCL has TCR ab which is CD56 – and has a better prognosis than the other group which has TCR γδ and is CD56 +.
Evaluation of the degree of cellular proliferation of malignant cells can be done by immunohistochemical techniques using Ki-67 antigen that is expressed in the G1, S, G2 phases of the cell cycle (not in the G0 phase), the highest levels being found in the M phase. Its expression is associated with a high mitotic count and a high histology grade. When the Ki-67 index is higher than 20%, there is a shortened overall survival period and increased chance of development of metastasis.[6
] Our patient had a Ki-67 index of 70–80% that warranted an aggressive line of therapy. However, our patient did not want chemotherapy and because she had a high Ki-67 index, corticosteroid treatment was started. This approach may be justified because patients who are CD56 – carry a good prognosis.