A 22-year-old woman with no significant past medical history presented with a rapidly progressing right axillary violaceous plaque (measuring 2.0 X 1.4 cm) over a period of three weeks. Skin punch biopsy (Figure A) was performed, which demonstrated atypical CD3-positive T-cells as pictured in the figures. These cells co-expressed CD2, CD5 (partial), CD7 (very dim), CD56 (partial), TCR delta, TIA1 and granzyme B and lacked staining for CD4, CD8, CD20, CD30, CD138, TCR BF1, Cyclin D1, and EBER.
The correct answer is ...
Primary cutaneous gamma delta T-cell lymphoma
The clinical picture with the provided microscopic findings are highly suggestive of cutaneous lymphoproliferative disease. Diagnosis of a cutaneous T-cell lymphoma requires the presence of cytologically atypical T-cells, which often show an aberrant immunophenotype, sometimes requiring genetic corroboration to demonstrate clonality.
Morphologically, this case shows significant atypia. The neoplastic lymphoid cells are monomorphic, intermediate-sized, and have irregular nuclear contours. These cells infiltrate subcutaneous tissue and deep dermis and show adipocyte rimming (Figure B) and angiodestruction (Figure C). This pattern of lobular, panniculitis-like growth is typical for this lymphoma.
Immunophenotypically, our case shows partial expression of CD5, very dim CD7, partial CD56, dual CD4/CD8 negativity, and strong uniform expression of TCR delta with co-expression of cytotoxic markers TIA-1 and granzyme B. In combination, the above findings best support a diagnosis of primary cutaneous gamma delta T cell lymphoma.
In most cases, this rare T-cell cutaneous lymphoma has an aggressive clinical course with frequent mucosal and extracutaneous dissemination and the risk of hemophagocytic lymphohistiocytosis. Cases are often CD4-/CD8- but can occasionally express CD8. The 5-year overall survival is poor at 11% to 33%.
Mohammad Barouqa, M.D.
Daniel Larson, M.D.
Senior Associate Consultant, Hematopathology