A Rare Case of Primary Cutaneous Diffuse Large B-Cell Lymphoma, Leg Type

CASE REPORT

A 74-year-old woman presented with a painful lesion on the left lower leg that was getting larger and more edematous and erythematous over the last 5 months. She experienced numbness and burning of the left lower leg 1 year prior to the development of the lesion. A review of her medical history revealed an otherwise healthy woman with no constitutional symptoms of fever, chills, nausea, vomiting, diarrhea, or chest pain. The patient did not exhibit mucosal, genital, or nail involvement. Physical examination revealed a group of four 1-cm, ill-defined, irregularly bordered, violaceous plaques on the left anterior tibial leg with faint surrounding erythematous to violaceous patches (Figure 1). The plaques were tender to palpation with no bleeding or drainage.

Figure 1. Primary cutaneous diffuse large B-cell lymphoma, leg type presenting as a violaceous, ill-defined, tender plaque with both surrounding and satellite faint erythematous to violaceous patches.

An 8.0-mm punch biopsy of the lesion was obtained. Hematoxylin and eosin staining on low-power magnification demonstrated a diffuse lymphocytic inflammatory infiltrate in the dermis and subcutis. Notable sparing of the subepidermal area (free grenz zone) was present (Figure 2A). On higher power, centroblasts and immunoblasts were visualized alongside extravasated red blood cells (Figure 2B). A diagnosis of primary cutaneous diffuse large B-cell lymphoma, leg type (DLBCLLT) was made. Various immunohistochemical stains confirmed the diagnosis, including B-cell lymphoma 2 (BCL-2)(Figure 3A) and multiple myeloma oncogene 1 (MUM-1)(Figure 3B), which were highly positive in our patient. The patient had a negative bone marrow biopsy and positron emission tomography scan. She was started on rituximab infusions and multiple radiation treatments. At 2-year follow-up the lymphoma continued to recur despite radiation therapy.

Figure 2. Histopathology of primary cutaneous diffuse large B-cell lymphoma, leg type demonstrated a diffuse inflammatory infiltrate in the dermis and subcutis with a subepidermal free grenz zone on low power (A)(H&E). High-power view demonstrated centroblasts and immunoblasts alongside extravasated red blood cells (B)(H&E).

Figure 3. Positive B-cell lymphoma 2 (BCL-2)(A) and multiple myeloma oncogene 1 (MUM-1)(B) immunohistochemical staining confirmed the diagnosis.

COMMENT

Incidence and Clinical Characteristics

Primary cutaneous DLBCLLT is an intermediately aggressive form of primary cutaneous B-cell lymphoma (CBCL) that accounts for approximately 10% to 20% of all primary CBCLs and 1% to 3% of all cutaneous lymphomas.¹ Diffuse large B-cell lymphoma, leg type primarily affects elderly patients (median age, 70 years). Women are more commonly affected. Clinically, primary cutaneous DLBCLLT presents as red-brown to bluish nodules or tumors on one or both distal legs. Although referred to as leg-type diffuse large B-cell lymphoma, 10% to 15% of patients have lesions in anatomic areas other than the legs, most commonly the trunk.

Histopathology

The diagnosis of DLBCLLT is best made histologically. There is a dense inflammatory infiltrate present in the dermis and subcutis that may extend upward into the dermoepidermal junction. Often a subepidermal free grenz zone may be seen, and adnexal structures may be destroyed. This infiltrate is composed of confluent sheets of large round cells including centroblasts and immunoblasts.² Centroblasts are large cells that have nuclei with several small nucleoli adhering to the membrane, while immunoblasts are large round cells containing nuclei with large central nucleoli. Both centroblasts and immunoblasts stain positively for BCL-2. Centrocytes typically are absent. Staining for BCL-2 can be important in distinguishing DLBCLLT from other forms of CBCL. Diffuse large B-cell lymphoma, leg type also can demonstrate clusters of large atypical cells in the epidermis simulating epidermotropism and Pautrier microabscesses. Neoplastic cells in this condition may express monoclonal surface and cytoplasmic immunoglobulins. Primary cutaneous DLBCLLT typically is positive for B-cell markers CD20 and CD79a. Additionally, MUM-1/IRF4 (interferon regulatory factor 4) and forkhead box protein 1 (FOXP1) are strongly expressed by most patients, which helps distinguish it from other forms of CBCL.

Treatment

Diffuse large B-cell lymphoma, leg type is a relatively aggressive form of CBCL that requires more aggressive treatment than the conservative watchful waiting of some of the more indolent forms of primary CBCL. One regimen involves using cyclophosphamide, doxorubicin, vincristine, and prednisone plus rituximab. Local chemotherapy or radiation with rituximab is another treatment option.^1,2 In patients with severe comorbidities, rituximab alone may be administered. The prognosis for DLBCLLT is not as favorable as other types of primary CBCL, with an estimated 5-year survival rate of approximately 50%.²