Case of the Month
A 56-year-old female presented with generalized lymphadenopathy. An inguinal lymph node was excised; its histology is shown in the images (inset shows spirochete immunohistochemical stain).
Which of the following microorganisms is the most likely cause of these findings?
a. Chlamydia trachomatis
b. Treponema pallidum
c. Rickettsia rickettsii
d. Mycobacterium avium-intracellulare
We will reveal the answer next month.
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Submitted by Anamarija M. Perry, Associate Professor of Pathology, and Lauren B. Smith, Professor and Director of Hematopathology at the University of Michigan, Ann Arbor, Michigan, USA.
Answer to December's Case of the Month
D. Primary cutaneous follicle center lymphoma
The images indicate a diagnosis of primary cutaneous follicle center lymphoma (PCFCL). This disease presents clinically with solitary or grouped erythematous, painless, non-pruritic papules, plaques, or tumors with a predilection for the head, neck, and trunk (1). Despite recurrences (observed in up to 50 percent of cases), prognosis is excellent.
Histopathology reveals nodular-to-diffuse infiltrates within the dermis extending into the subcutaneous fat, sparing the epidermis and papillary dermis. Thise case shows a follicular pattern with germinal center formation. The neoplastic infiltrate contains centrocytes (small and large cleaved follicle center cells) and centroblasts (large follicle center cells with prominent nucleoli) admixed with variable numbers of small lymphocytes. Abnormal follicles appear as irregular aggregates of larger cells with prominent eosinophilic stroma. In addition, they have diminished or absent mantle zones and often lack tingible body macrophages. Virtually all cases express pan B-cell antigens (CD19, CD20, and CD79a) and are always CD5-negative. CD10, CD21, and BCL-6 positivity can be observed more frequently in germinal center lymphomas with a follicular pattern than in cases with a diffuse histologic pattern. The plasma cell marker MUM1/IRF4 is negative. Bcl-2 expression is found only in a minority of cases of PCFCL (2).
Cutaneous B-cell pseudolymphoma (previously called lymphocytoma cutis or cutaneous lymphoid hyperplasia) usually presents with erythematous nodules or plaques, preferentially located on the face or chest. Histologically differentiating pseudolymphoma from follicle center cell lymphoma can be difficult. Dense diffuse lymphoid infiltrates with prominent germinal centers. completely lacking a mantle zone and characterized by large numbers of blastic cells and tingible body macrophages, are characteristic of pseudolymphoma. On the other hand, lack of tingible body macrophages within follicles is a strong hint for malignancy (3). Immunohistochemistry reveals distinct B and T cell compartments. Staining for CD35 or CD21 shows networks of follicular dendritic cells within reactive germinal centers and shows BCL-6 and CD10 positivity within germinal center lymphocytes only (3).
Primary cutaneous marginal zone lymphoma presents as small red-to-violaceous papules, plaques, or nodules that – unlike PCFCL – frequently occur in multiple locations. Histopathology reveals a characteristic pattern with nodular-to-diffuse infiltrates with sparing of the epidermis; these sometimes contain reactive germinal centers (4). Lymphoplasmacytoid cells, plasma cells, blasts, and eosinophils are also present. The neoplastic cells express CD20, CD22, CD79a, and BCL2 and are typically negative for CD3, CD5, CD10, and BCL6.
Primary cutaneous diffuse large B-cell lymphoma, leg type, presents clinically with reddish-to-bluish solitary or grouped tumors and plaques, which are most frequently located on the lower legs of elderly patients (especially females). Ulceration is common. The histological features show diffuse infiltrates predominantly composed of large B cells with variable proportions of immunoblasts and/or centroblasts. The neoplastic cells express B-cell markers. Expression of BCL-2, MUM1, FOXP1, and MYC proteins are common. Bcl-6 is frequently positive (5).
Cutaneous CD4+ small/medium-sized pleomorphic T-cell lymphoma is a rare neoplasm characterized by a predominance of small-to-medium-sized CD4+ pleomorphic T cells and PD1+ T cells without germinal center formation. This disease usually presents with a solitary plaque or tumor, generally on the face, neck, or upper trunk. They show dense, diffuse, or nodular infiltrates within the dermis that tends to infiltrate the subcutis (6).
Submitted by Muhammad Ahsan, Sahiwal Medical College, Sahiwal, Pakistan.
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