Solitary Erythematous Plaque on the Nasolabial Fold.

Sir,

Cutaneous B-cell lymphoma (CBCL) is a rare group of lymphoproliferative disorders of the skin, with varied clinical and histopathological features. We hereby report a case of primary cutaneous follicle center BCL in a man. A 59-year-old man presented with an asymptomatic solitary scaly elevated lesion near the nose, present over the preceding 4 months. There was no history of drug intake, trauma, application of any cream or ointment, insect bite, tattooing, etc. Cutaneous examination revealed a solitary erythematous scaly plaque (2 cm in diameter) over the nasolabial fold on the right side [Figure 1]. The surface was rough, mildly indurated, and the consistency was firm. Regional lymphadenopathy was absent. Clinical differential diagnoses were cutaneous lymphoid hyperplasia, inclusion cyst, Merkel cell carcinoma, etc. Histopathology revealed a well-circumscribed nonepidermotropic intensely basophilic nodular infiltrate in the dermis, comprising of lymphocytes, centrocytes, centroblasts, plasma cells, tingible body macrophages, and inflammatory cells. A distinct grenz zone could be appreciated. A mantle zone of lymphocytes surrounding the dermal nodule was absent. The infiltrate was predominantly composed of small to medium-sized lymphoid cells with indented nuclei and abundant, pale cytoplasm [Figures 2 and 3]. Immunohistochemistry findings showed the cells to be CD19+, CD20+, Bcl-2+, and Ki67+ (19%). The patient was prescribed halobetasol cream, twice daily for 2 weeks which resulted in dramatic improvement of the lesions. Based on clinicopathological correlation, a diagnosis of primary cutaneous follicle center BCL was done.

Figure 1

Solitary erythematous scaly plaque over the nasolabial fold

Figure 2

Photomicrograph showing well-circumscribed intensely basophilic nodular infiltrate of lymphocytes, centrocytes, centroblasts, plasma cells and tingible body macrophages. Note the distinct grenz zone (H and E, ×100)

Figure 3

Photomicrograph showing centroblasts (red arrow), centrocytes (green arrow) and tingible body macrophages (blue arrow) (H and E, ×400)

Cutaneous lymphomas are defined as a group of lymphoproliferative skin infiltrates of T-cell, B-cell, or natural killer cell lineage.[1] According to the WHO/EORTC classification of CBCLs, there are four types including primary cutaneous marginal zone BCL, primary cutaneous follicle center lymphoma (PCFCL), cutaneous diffuse large BCL (leg type and others), and intravascular large BCL.[2]

Primary follicle center BCL manifests as pink to violaceous nodules and plaques, over head and neck. Histopathologically, it shows proliferation of CD20+ centrocytes and centroblasts, in follicular or diffuse (or both) patterns.[3] On immunohistochemistry, the cells are CD19+, CD20+, CD22+, CD43+, CD79a+, Bcl-6+, and Bcl-2−. Bcl-2 positivity is not a universal finding. In a study of 19 cases, 11 patients were Bcl-2+.[4]

CBCL has to be differentiated from cutaneous T-cell lymphoma (CTCL) and B-cell pseudolymphoma (PSL). CTCL is characterized by classical clinical features, for example, mycosis fungoides evolves from the stage of patch to plaque, tumor, and erythroderma. On histopathology, the pattern of growth is horizontal, disk-like, and epidermotropic. However, the pattern in CBCL is spherical and nonepidermotropic. B-cell PSL presents as a solitary soft nodule on the head and neck areas; following an infection, trauma, irritation, etc. The papulonodules of CBCL are firm to hard. Lymphoid infiltrate in CBCL is dome-shaped with a convex border of infiltrative nodules. In PSL, it is wedge shaped, showing concave borders of infiltrate. Besides in PSL, there is the formation of germinal centers. Our patient had presented with a solitary firm to hard plaque on the face, histologically consistent with PCFCL. The neoplastic follicles of PCFCL consist of centrocytes (small to large cells with “stretched toffee” like nuclei) and centroblasts (large cells with oval to round nuclei).

To note, Bcl-2 positivity differentiates a benign lymphoid hyperplasia from a neoplastic follicle. If Bcl-2 is positive, it indicates that the lesion is a low-grade BCL, and it is essentially negative in high-grade lymphomas. Consistent with Bcl-2 positivity in our case, the patient had been suffering from low-grade PCFCL, and that is why the lesion responded dramatically to potent topical steroid alone. Similar to our case, Bachmeyer et al. had reported a case of multifocal primary cutaneous marginal zone BCL, which showed excellent response to topical mechlorethamine and clobetasol.[5]

Pseudolymphomatous folliculitis is a close clinical differential for our case. It is characterized by a solitary dome-shaped or flat-elevated nodule located on the face, scalp, and trunk. On immunohistochemistry, distribution of CD1a+ dendritic cells around hypertrophic hair follicles is a diagnostic finding in pseudolymphomatous folliculitis. Management of such cases can be done using excision, local radiotherapy, cryotherapy, topical treatment (corticosteroids, imiquimod, nitrogen mustard, and bexarotene), intralesional (corticosteroids, interferon-alfa, rituximab), and antibiotics (if evidence of Borrelia burgdorferi infection present). Intralesional rituximab is a good therapeutic option in such cases. Since CBCL express CD20 molecule, patients with histologically and immunohistochemically confirmed cases respond well to rituximab.[67]

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