A spindle cell variant of diffuse large B-cell lymphoma possesses genotypic and phenotypic markers characteristic of a germinal center B-cell origin

Spindle cell cutaneous epitheliotropic T-cell lymphoma in an American Bulldog

An 8-year-old American Bulldog developed coalescing exophytic bulbous nodules that grew rapidly on the left pinna and a single cutaneous mass on the left flank. Histological examination of the pinnal biopsy by a diagnostic laboratory revealed a densely cellular neoplasm with haphazardly arranged round to spindle cells with high mitotic activity and epitheliotropism. The initial diagnosis was a poorly differentiated malignant neoplasm with differential diagnoses including melanoma, tumour of histiocytic origin and, less likely, a pleomorphic lymphoma. A panel of melanoma immunohistochemical markers and immunolabelling for CD18 were pursued. Neoplastic cells were immunopositive for CD18 but negative for Melan-A, PNL2, TRP-1 and TRP-2, suggestive of a histiocytic tumour or lymphoma. The left ear masses recurred, and more masses developed on the body. The pinnectomized ear was submitted to the University of Missouri Veterinary Medical Diagnostic Laboratory. Similar cells were seen and were immunolabelled for CD18 and CD3 but were immunonegative for SOX10, CD79a and CD20. PCR for antigen receptor rearrangements revealed a clonal rearrangement of T-cell receptor gamma. These findings enabled a final diagnosis of epitheliotropic T-cell lymphoma with spindle cell morphology. Lymphoma should be considered as a potential differential diagnosis for cutaneous nodules of spindle cell morphology and lymphocytic immunohistochemical markers should be included in diagnostic panels.

Follicular Dendritic Cell Sarcoma of Uterine Corpus: Report of 2 Cases

Follicular dendritic cell sarcoma is a rare dendritic/histiocytic tumor of intermediate malignant potential, which often involves extranodal sites, most commonly the gastrointestinal tract and mediastinum with only 5 cases reported in the female genital tract. We present the clinical and pathologic features of 2 such examples arising in the uterine corpus. Both patients (63 and 72-yr old) presented with postmenopausal bleeding and underwent an endometrial biopsy diagnostic of follicular dendritic cell sarcoma that was followed by hysterectomy. The tumors were polypoid, 3.5 and 5.0 cm, and were confined to the endometrium. Microscopically, ovoid to round to spindled tumor cells with pale eosinophilic cytoplasm and vesicular nuclei were arranged predominantly in sheets with an accompanying lymphocyte-rich inflammatory infiltrate. The tumor cells were positive for CD35, CD23, D2-40 in both tumors and additionally positive for CD21 in 1 tumor, all highlighting cell bodies and processes. Patients were alive without evidence of disease at 1 and 4 years with no adjuvant treatment. These cases highlight the importance of entertaining a broad differential diagnosis in lesions with epithelioid and/or spindled morphology involving the uterus.

PAX8 Distinguishes Diffuse Large B-Cell Lymphoma Mimicking Sarcoma

PAX8 is important for embryogenesis of the thyroid, Müllerian system, and upper urinary/renal tract, and expression of PAX8 has been described in carcinomas from each of these sites. The sensitivity and specificity of the polyclonal PAX8 antibody in a large cohort of epithelial tumors as well as lymphomas have been previously determined, the latter because polyclonal PAX8 is known to be immunoreactive in nonneoplastic B-cell lymphocytes which are often used as the positive internal control for immunohistochemistry. In this case report, PAX8 was a diagnostic clue for revising a previous diagnosis of unclassified high grade sarcoma to diffuse large B-cell lymphoma. This case report demonstrates a pitfall for PAX8 immunoreactivity and acts as a reminder that lymphoma should be included in the differential diagnosis of a PAX8 positive, epithelial cell marker negative tumor of unknown primary origin.

Primitive "Spindle Cell Variant" (Sarcomatoid Variant) Diffuse Large B-Cell Lymphoma of the Uterine Cervix: Description and Outcome of a Rare Case

A very rare case of primary diffuse large B-cell lymphoma of the uterine cervix characterized by "spindle cell variant" morphology ("sarcomatoid subtype") is described along with a discussion of the challenging diagnosis due to its rarity and presenting clinical and pathological features.

Primary cutaneous B-cell lymphomas with large cell predominance-primary cutaneous follicle center lymphoma, diffuse large B-cell lymphoma, leg type and intravascular large B-cell lymphoma

In this review, we present clinical features and detailed histopathologic, immunologic, and molecular information regarding primary cutaneous follicle center lymphoma and primary cutaneous diffuse large B-cell lymphoma, leg type which together represent two of the three most common types of primary cutaneous B-cell lymphoma recognized in the current WHO classification system.^1,2 Overall, B-cell lymphomas represent 19-27% of primary cutaneous lymphomas in most large European and American studies^3-6 and together, primary cutaneous follicle center lymphoma and primary cutaneous diffuse large B-cell lymphoma, leg type account for approximately 2/3 to ¾ of these cases.^5,7-11 Both subtypes can contain a high content of large B-lymphocytes, although most cases of primary cutaneous follicle center lymphomas exhibit a range in cell size and cytology. Intravascular large B-cell lymphoma, a less commonly-encountered EBV-negative primary cutaneous B-cell lymphoma composed of large cells, will be more briefly discussed in this report as well.

A rare spindle-cell variant of non-Hodgkin's lymphoma of the mandible

A 64-year-old male farmer presented with a rapidly progressive swelling of the left mandible since 6 months. The swelling was firm to hard, diffuse, nontender, obliterating the vestibule with paresthesia of lower lip. The cone beam computed tomography imaging revealed an ill-defined, moth-eaten radiolucency with destruction of the buccal and lingual cortical plates. The rapid growth and aggressive behavior of the lesion coupled with guidance from the patient's previous reports from the incisional biopsy and fine needle aspiration cytology warranted a mandibular resection. Microscopic examination showed an encapsulated lesion situated in the connective tissue containing a mixture of proliferating spindle-shaped cells arranged in fascicles and round cells infiltrating into the connective tissue stroma and bone. The neoplastic cells exhibited atypical features such as pleomorphism, hyperchromatism and increased mitotic figures with noncleaved nuclei. A working diagnosis of a spindle-cell sarcoma was arrived at with various differentials provided such as fibrosarcoma, rhabdomyosarcoma, leiomyosarcoma, malignant peripheral nerve sheath tumor, Langerhans cell histiocytosis and lymphoma and stating the need for immunohistochemistry to subtype the tumor. The neoplastic cells were negative for Van Gieson's stain and Masson's trichrome. Immunohistochemical analysis performed using desmin, smooth muscle actin, S-100 and CD1a in a bid to determine the phenotype of the tumor and rule out the previously stated differentials were all negative for the lesion. Lymphoid markers such as leukocyte common antigen and CD20 (cluster differentiation marker for B-cells) showed positivity in spindle-shaped cells as well as round cells indicating the tumor to be a lymphoproliferative lesion of B-cell type. A final diagnosis of “spindle-cell variant of non-Hodgkin's lymphoma” was rendered based on the immunohistochemical profile.

A spindle cell variant of diffuse large B-cell lymphoma is characterized by T-cell/myofibrohistio-rich stromal alterations: analysis of 10 cases and a review of the literature

Spindle-shaped diffuse large B-cell lymphoma (Sp-DLBCL) has been recognized as a rare morphologic variant of DLBCL. However, the biological processes that contribute to the specific features of Sp-DLBCL remain poorly understood. In this study, a combined immunophenotypic and genetic analysis was performed in 10 Sp-DLBCL. First, we investigated several unique markers for anaplasia (CD30, ALK, CD68, and EBER-ISH), mesenchyma (SMA, desmin, and vimentin), and B-cell differentiation (CD10, BCL6, and MUM1). We also performed conventional cytogenetic and fluorescence in situ hybridization studies to look for common chromosomal break points (BCL2, BCL6, and MYC). We found that most Sp-DLBCLs were germinal center B cell-like and that none had any other specific phenotypes or any karyotypic abnormalities. Instead, T cells, CD68-positive macrophages and SMA-positive myofibroblasts were significantly increased in Sp-DLBCL when compared with conventional GCB origin DLBCL cases (n = 10) (P = 0.012, P < 0.001, and P < 0.0001, respectively). To further characterize Sp-DLBCL, we next compared the expression of fibroblast growth factor 2 (FGF2) and transforming growth factor-β1 (TGFβ1) between the two types of DLBCL. Finally, we confirmed that the number of FGF2- and TGFβ1-positive stromal cells was markedly increased in Sp-DLBCL and that the difference between these and conventional GCB origin DLBCLs was significant (P < 0.0001 and P = 0.0017, respectively). Thus, T-cell/myofibrohistio-rich stromal alterations in Sp-DLBCL, especially those mediated by TGFβ1 and FGF2, may play a role in the transition of lymphoma cells into those with spindle-shaped features.

The host genetic background of DNA repair mechanisms is an independent predictor of survival in diffuse large B-cell lymphoma

Several drugs used for diffuse large B-cell lymphoma (DLBCL) treatment rely on DNA damage for tumor cell killing. We verified the prognostic impact of the host DNA repair genotype in 2 independent cohorts of DLBCL treated with R-CHOP21 (training cohort, 163 cases; validation cohort, 145 cases). Among 35 single nucleotide polymorphisms analyzed in the training series, MLH1 rs1799977 was the sole predicting overall survival. DLBCL carrying the MLH1 AG/GG genotype displayed an increased death risk (hazard ratio [HR] = 3.23; P < .001; q =0 .009) compared with patients carrying the AA genotype. Multivariate analysis adjusted for International Prognostic Index identified MLH1 AG/GG as an independent OS predictor (P < .001). The poor prognosis of MLH1 AG/GG was the result of an increased risk of failing both R-CHOP21 (HR = 2.02; P = .007) and platinum-based second-line (HR = 2.26; P = .044) treatment. Survival analysis in the validation series confirmed all outcomes predicted by MLH1 rs1799977. The effect on OS of MLH1, a component of the DNA mismatch repair system, is consistent with its role in regulating the genotoxic effects of doxorubicin and platinum compounds, which are a mainstay of DLBCL first- and second-line treatment.

Activation-induced cytidine deaminase expression in diffuse large B-cell lymphoma with a paracortical growth pattern: a lymphoma of possible interfollicular large B-cell origin

CONTEXT

Activation-induced cytidine deaminase, necessary for immunoglobulin somatic hypermutation and class switch recombination, is usually expressed within the follicular dendritic network but is also expressed in a population of interfollicular large B cells outside the germinal center.

OBJECTIVE

To report 7 cases of diffuse large B-cell lymphoma with a distinct paracortical distribution. Expression of activation-induced cytidine deaminase, previously described in interfollicular large B cells, was evaluated.

DESIGN

A panel of immunohistochemical markers, including double staining for activation-induced cytidine deaminase and CD20, was used to illustrate the cases. Molecular studies were performed by polymerase chain reaction in the paraffin-embedded tissue for t(14;18) chromosomal translocation and immunoglobulin heavy chain and T-cell receptor rearrangements.

RESULTS

Patients included 3 males and 4 females ranging in age from 11 to 59 years (mean, 39 years). All specimens were lymph nodes (4 from the groin, 2 from the neck, and 1 from the axilla). Malignant lymphocytes were positive for CD20 and negative for CD5 and CD10. Staining for CD30, CD43, and BCL-2 was variable. The malignant cells showed at least focal staining with activation-induced cytidine deaminase. All cases were found to be monoclonal by immunoglobulin heavy-chain gene rearrangement or showed light-chain restriction. None of the tested cases showed t(14;18).

CONCLUSIONS

Diffuse large B-cell lymphoma with a paracortical distribution is unusual and may be a distinct morphologic variant. More study is necessary to determine the stage of B-cell development and the cell of origin of these tumors. However, activation-induced cytidine deaminase expression suggests they may arise from a putative interfollicular large B cell.

Diffuse large B-cell lymphoma: a heterogeneous group of non-Hodgkin lymphomas comprising several distinct clinicopathological entities

Diffuse large B-cell lymphoma (DLBCL) as defined by the World Health Organization (WHO) classification is clinically, morphologically and genetically a heterogeneous group of malignant proliferations of large lymphoid B cells. Over the last 6 years, several studies have been published improving our understanding of these lymphomas. These studies analyzed DLBCL by their gene expression profile, provided further information on some of the variants of DLBCL listed in the WHO classification and stressed the impact of the site of origin of these tumors. This review summarizes these recent data and explores their impact on the recognition of new clinicopathological lymphoma entities.