Case One – January 2017 – SkinPath Solutions

Patient Info

Histology

There is a dense perivascular, perifollicular & interstitial cellular lymphoid infiltrate, extending into subcutis. Areas of hemorrhage

The infiltrate consists of a uniform population of cells with basophilic cytoplasm, round to oval nuclei, & small nucleoli.

Immunohistochemistry

CD45+ (confirming lymphoid origin)
Negative for mature B- and T-cell markers- CD3, CD5, CD7, CD20, CD79a.
Negative for myeloid markers of AML like MPO, CD34, c-kit, lysozyme, CD33, CD68 (but can be TdT+)
CD4+ CD8-
CD56+
CD123+ TCL-1+ (Marker of plasmacytoid dendritic cells)

Differential Dx

Extranodal NK/T-cell lymphoma:
This tumor is also CD56+, but CD4-.
Also it is consistently positive for EBV; but BDCN is EBV negative.
TCL-1 and CD123 are expressed almost exclusively in BDCN.

Final Diagnosis

Blastic Plasmacytoid Dendritic Cell Neoplasm Facts

BPDCN accounts for < 1% of all acute leukemia cases & 0.7% of cutaneous lymphomas.
The male : female ratio is ≥ 3:1.
Most patients are elderly (mean age of 67 years at presentation).
Almost all cases have cutaneous lesions at presentation, & there is frequent involvement of BM & peripheral blood (60–90%) & LNs(40–50%), although virtually any organ can be affected.

Lesions can be solitary or multiple Affecting head, neck, trunk or extremities, Erythematous, violaceous or red-brown- nodules, tumors or plaques or Bruise-like lesions (as in our patient)

The clinical course is aggressive with involvement of BM, PB, & other sites, and the development of cytopenia.
Initial responses to treatment are relatively common, but most patients relapse within a short space of time.
Poor prognosis with Median survival time only 12–14 months (estimated 5-year survival is 0%).
In 10–20% of cases, BPDCN is associated with, or develops into, a myelodysplastic syndrome, myelomonocytic leukemia or acute myeloid leukemia.

What is this tumor, and why should I know about it?

This is a very clinically aggressive tumor derived from the precursors of plasmacytoid dendritic cells.
It has a high frequency of cutaneous, bone marrow & peripheral blood involvement with leukemic dissemination.
In most cases the neoplasm is confined to the skin at presentation.
However, leukemic spread after variable, usually short, periods of time is the rule, indicating that the primary cutaneous cases most likely represent “aleukemic” phase of leukemia cutis.
Listed in the WHO book on Classification of Tumours of Hematopoietic and Lymphoid Tissues in section on Acute Myeloid Leukemia.

In the past known by various names like:

Blastic NK-cell lymphoma
Blastic NK-cell leukemia/lymphoma
CD4+ CD56+ hematodermic neoplasm/tumor

Summary

Important to remember this very aggressive lymphoma with a high frequency of leukemic dissemination.
Skin lesions are most often the 1st presenting manifestation of the disease.
Cutaneous lesions can be bruise-like or pigmented simulating melanoma.
Histology can pose a diagnostic challenge.
Because of its aggressive behavior it is important to correctly diagnose it in a timely fashion for proper clinical management.