[Blastic plasmacytoid dendritic cell neoplasm - a rare differential diagnosis of neoplastic skin infiltrations associated with systemic symptoms].

HISTORY AND CLINICAL FINDINGS

A 70-year-old female patient developed a non-pruritic, indolent rash associated with infections and peripheral blood abnormalities. A skin biopsy was suggestive of malignant lymphoma of the skin.

INVESTIGATIONS

The peripheral blood count showed mild pancytopenia and 12 % blasts. Additional immunohistochemistry of the skin specimen as well as cytologic and flow cytometric examination of the bone marrow revealed an immature cell population expressing CD4 and CD56 which infiltrated both the dermis and, with an infiltration grade of about 85 %, the bone marrow.

DIAGNOSIS

Blastic plasmacytoid dendritic cell neoplasm (formerly known as blastic NK cell lymphoma).

TREATMENT AND COURSE

After the first course of induction chemotherapy with daunorubicin and cytarabin, both the rash and the hematologic findings of bone marrow and peripheral blood showed a complete remission.

CONCLUSION

The blastic plasmacytoid dendritic cell neoplasm is a rare, aggressive hematopoietic neoplasm most likely related to acute myeloid leukemia (AML). Since cutaneous involvement is regularly present at diagnosis, the differential diagnosis of unexplained skin lesions should include this disease entity, especially if peripheral blood abnormalities are present. Despite the initial response to cytostatic therapy being mostly excellent, the prognosis is poor. Hence, treatment as high-risk AML seems advisable.