SAN FRANCISCO The diagnosis of blastic natural killer-cell lymphoma requires a dermatopathologist who knows the typical immunohistochemical patterns of the disease and is aware of exceptions to rules.
Also called CD4-positive, CD56-positive (CD4+/CD56+) hematodermic neoplasm, the disease is a rare, aggressive malignancy that frequently presents with skin lesions. Immunohistochemical staining typically produces immunopositivity for CD4, CD56, and CD123, but rare cases have been reported of patients who tested negative in one or more of these immunohistochemical studies.
At the annual meeting of the American Society of Dermatopathology, Dr. Rajwant Malhotra and Dr. Alison L. Uzieblo reported on two cases of CD4+/CD56+ hematodermic neoplasm presenting as skin nodules and plaques. One of the cases in their poster was CD123-negative.
"Loss of CD123 expression is a distinctly unusual event" in CD4+/CD56+ hematodermic neoplasm, wrote the authors, both from the anatomic pathology department at Beaumont Hospital, Royal Oak, Mich. Given the poor prognosis associated with this disease, "it is important to be aware of this potential phenomenon when evaluating cutaneous hematolymphoid malignancies."
One patient was a 77-year-old man who presented with skin lesions on his back and trunk. Flow cytometric analysis subsequently showed bone marrow involvement. The second patient, a 70-year-old man, had a 3-cm nodular plaque on his scalp. Further clinical evaluation found no evidence of bone marrow involvement.
Histological examination of biopsies from both patients revealed dense dermal infiltrates composed of sheets of medium-sized cells with angulated to round nuclear contours in the dermis. The lesional cells were positive for CD4, CD43, and CD56, but only one patient's biopsy demonstrated CD123 positivity. Both showed a high proliferation rate with Ki-67 staining noted in approximately 50% of cells in one patient and 70% of cells in the other.