Cutaneous Spindle-Cell B-Cell Lymphomas: Most are Neoplasms of Follicular Center Cell Origin

Recent advances in cutaneous lymphoma-implications for current and future classifications

The Revised European-American Classification of mature lymphoid neoplasms published in 1994 and the 2001, 2008 and 2016 WHO classifications that followed, were the product of international collaboration and consensus amongst haematopathologists, geneticists, molecular scientists and clinicians. Primary cutaneous lymphomas were fully incorporated into this process following the publication of the WHO-EORTC classification of cutaneous lymphomas in 2005. The definition, diagnostic criteria and recommended studies for primary cutaneous lymphoma continue to be refined. The 2022 International Consensus Classification represents the most recent update and an overview of all the main entities presenting primarily in the skin, together with the major changes in classification, are summarized herein. Primary cutaneous marginal zone lymphoma is segregated from other extranodal marginal zone lymphomas of mucosa-associated lymphoid tissue (MALT lymphoma) and downgraded to a lymphoproliferative disorder in line with its markedly indolent behaviour. In addition, two subtypes are recognised, based largely but not exclusively on whether they are heavy chain class-switched or IgM positive. Similarly, in keeping with a trend to greater conservatism, primary cutaneous acral CD8 positive T cell lymphoma is now also classified as a lymphoproliferative disorder. In addition, significant new insights into the biology of primary cutaneous lymphoma have also recently been forthcoming and will be presented. These studies have enhanced our knowledge of genetic, epigenetic and transcriptional changes in this group of diseases. They not only identify potential targets for novel therapies, but also raise as yet unanswered questions as to how we categorise cutaneous lymphomas, particularly with respect to relationships with similar lymphomas at extracutaneous sites.

Spindle Variant Primary Diffuse Large B Cell Lymphoma of the Colon: Case Report and Literature Review

Diffuse large B cell lymphoma (DLBCL) with spindle cell morphology is a rare variant that can be seen in extranodal regions. Because the spindle cell dominant morphology in lymphoma is extremely unusual, the diagnosis can easily be missed in many organ systems. We present a case of an 82-year-old male patient with complaints of abdominal pain and swelling. He operated with the preliminary diagnosis of cecum tumor and ileum perforation. Tumoral proliferation was observed originating from the submucosa and infiltrating the muscularis propria, with the features of mostly spindle-shaped, having round-shaped nuclei in some of the cells, and having relatively narrow cytoplasm. A panel of immunohistochemical stains were performed to rule out the possibilities of sarcoma, carcinoma, or melanoma. Diffuse strong positive reaction was observed for CD45, CD20, CD19, CD22, Pax5, and CD30. The case was reported as spindle cell variant of DLBCL based on the present findings. As far as we know, this is the first case described in the colon. We emphasize that pathologists should be reminded of lymphoma as a differential diagnosis of spindle cell tumors.

Spindle-cell (Sarcomatoid) Variant of Cutaneous Anaplastic Large-cell Lymphoma (C-ALCL): An Unusual Mimicker of Cutaneous Malignant Mesenchymal Tumors-A Series of 11 Cases

Cutaneous anaplastic large-cell lymphoma (C-ALCL) represents one of the entities within the group of CD30-positive lymphoproliferative disorders of the skin. Most cases are ALK-negative, though isolated cases of ALK-positive C-ALCL have also been reported. By definition, the diagnosis of C-ALCL requires the expression of CD30 in >75% of the cells. Histopathologically, C-ALCL shows a dermal-based nodular and circumscribed proliferation of large pleomorphic cells with vesicular nuclei, prominent nucleoli, and eosinophilic cytoplasm, including hallmark cells. Since 1990, isolated case reports of a so-called "sarcomatoid" variant have been published in the literature. Herein, we present a series of 11 cases of spindle (sarcomatoid) C-ALCL, with comprehensive histopathologic, immunophenotypic, and molecular data. Spindle C-ALCL represents a potential mimicker of malignant mesenchymal or hematopoietic tumors in the skin and should always be considered in the differential diagnosis when assessing cutaneous pleomorphic spindle cell neoplasms.

[Hematological neoplasias as differential diagnoses of soft tissue tumors]

BACKGROUND

Several hematological malignancies might morphologically present as differential diagnoses of sarcomas.

OBJECTIVES

To illustrate entities of hematological malignancies that might cause difficulties in differentiation from sarcomas and to introduce immunohistochemical and molecular tests that facilitate the diagnosis.

MATERIAL AND METHODS

Selective literature research ( http://www.ncbi.nlm.nih.gov ) was combined with the clinico-pathological experience of the authors.

RESULTS

In particular, hematologic malignancies with small blue round cell cytology, as well as lymphomas with anaplastic or spindle cell morphology, may mimic sarcomas. Identification of the correct diagnosis is usually possible by applying immunohistochemical and molecular analyses. Lymphomas without expression of CD45 and hematological neoplasias with expression of markers characteristic of sarcomas may cause difficulties in differential diagnosis.

CONCLUSION

Hematological malignancies should be kept in mind as differential diagnoses of sarcomas and should be excluded by immunohistochemical and molecular analyses according to morphology and the clinical picture.

Primary Cutaneous Follicle Center Lymphoma Clear Cell Variant: Expanding the Spectrum of Cutaneous Clear Cell Neoplasms

Primary cutaneous follicle center lymphoma is the most frequent cutaneous B-cell lymphoma despite the fact that is an uncommon disease. Mild biological behavior and good prognosis characterized this neoplasm with a low aggressiveness compared with classic nodal follicular lymphoma (FL). Rare histological variants have been described. We present the case of a 72-year-old man who underwent surgery for a cutaneous nodule on his left scapula. The biopsy showed a dermal clear cell proliferation arranged in a nodular and diffuse pattern. The cells stained positive for CD20 and Bcl-6 supporting B-cell follicular differentiation. The final diagnosis was "primary cutaneous follicle center lymphoma" with "clear cell changes" according to the 2016 World Health Organization classification of lymphoid neoplasms. Additional tests to rule out a systemic involvement were performed. The prognosis was favorable with a disease-free survival of 7 years after complete surgical excision. It has been assumed that cutaneous tumors composed of clear cells may have an epithelial, melanocytic, adnexal, mesenchymal, or metastatic origin. The correct histopathological diagnosis required immunohistochemistry and even molecular techniques. To the best of our knowledge, this is the first report of a cutaneous clear cell lymphoma and of a FL with clear cell features. Our findings provide evidence that the heterogeneity of FL is greater than previously thought and expand the spectrum of differential diagnosis in cutaneous clear cell neoplasms. Dermatopathologists should be aware of this entity and should comprise a PanB marker in their first- or second-line immunohistochemistry for the correct diagnosis of a dermal clear cell proliferation.

Primary Cutaneous B-cell Lymphomas

B-cell lymphomas represent approximately 20% to 25% of primary cutaneous lymphomas. Within this group, most cases (>99%) are encompassed by 3 diagnostic entities: primary cutaneous marginal zone lymphoma, primary cutaneous follicle center lymphoma, and primary cutaneous diffuse large B-cell lymphoma, leg type. In this article, the authors present clinical, histopathologic, immunophenotypic, and molecular features of each of these entities and briefly discuss the rarer intravascular large B-cell lymphoma.

Primary cutaneous B-cell lymphoma: narrative review of the literature

Primary cutaneous B-cell lymphomas comprehend a group of lymphoproliferative disorders characterized by being monoclonal proliferations of B-cell primarily involving the skin. Despite being recognized as autonomous and distinct clinico-pathologic entities since the late 80s, their classification is still an ongoing matter of debate. At the moment, WHO classification recognizes three disorders: primary cutaneous marginal zone lymphoma, primary cutaneous follicle center lymphoma and primary cutaneous diffuse large b-cell lymphoma (leg type). Primary cutaneous diffuse large b-cell lymphoma (other) has been used to define rare cases which show histologically an infiltrate with diffuse pattern composed by large b-cell, but not fitting with criteria for follicle center lymphoma nor for primary cutaneous diffuse large b-cell lymphoma (leg type). Aim of this review was to briefly describe all recognized and provisional entities included in the primary cutaneous b-cell lymphomas and to discuss recent acquisitions that may influence their future classifications.

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.

Non-mesenchymal Mimics of Sarcoma

A variety of different non-mesenchymal neoplasms may mimic sarcoma, in particular sarcomatoid carcinoma and melanoma, but also mesothelioma and rarely some lymphomas. This article reviews the key clinical and histologic features of such neoplasms in different settings, along with the use of ancillary studies to help identify the tumor types most frequently misdiagnosed as sarcoma.