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B-cell and plasma cell proliferations are frequently observed in nodal T follicular helper (nTfh) cell lymphomas and can present a diagnostic challenge. These proliferations can be monotypic or monoclonal and morphologically resemble lymphoma or plasmacytoma, but their clinical behavior is poorly defined. In this study, we reviewed 414 cases of nTfh lymphoma seen over the past decade at our institution. We identified 78 (19%) cases that exhibited B-cell or plasma cell proliferation detected by morphology, flow cytometry, immunohistochemistry, and/or molecular techniques. The B-cell/plasma cell proliferations occurred before (22%), concurrently with (50%), or after (28%) the diagnosis of nTfh lymphoma. We divided them into 3 categories: (1) focal or scattered B-immunoblastic proliferations recognized morphologically without a monotypic/monoclonal B-cell population (17%), (2) monotypic/monoclonal B-cell/plasma cells identified solely by flow cytometry or molecular clonality studies without morphologic confirmation (11%), and (3) unequivocal B-cell/plasma cell expansions recognized by morphologic assessment (72%). We further subdivided group 3 into proliferations associated with and possibly dependent on neoplastic Tfh cells versus those proliferations occurring in the absence of neoplastic Tfh cells and likely bona fide lymphomas. Follow-up biopsy specimens showed persistence of B-cell/plasma cell proliferations in various patient subcategories, with transformation to higher-grade B-cell proliferation or persistence without Tfh cells in some cases. In conclusion, our data support the notion that most B-cell and plasma cell proliferations associated with neoplastic Tfh clones have little impact on the clinical course of patients with nTfh lymphoma and likely do not constitute an independent B-cell lymphoma, especially those of small B cells of plasma cells. However, B-cell expansions exhibiting aggressive morphologic features may represent an independent B-cell lymphoma., Competing Interests: Conflicts of Interest and Source of Funding: F.V. receives research funding from Allogene, Caribou, and Geron Corporation. For the remaining authors, none were declared., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Marginal zone lymphoma of the mucosa-associated lymphoid tissue (MALT lymphoma) represents 8% of all B-cell lymphomas and it is the most common small B-cell lymphoma arising at extranodal sites. The gold-standard test to establish a diagnosis of MALT lymphoma remains histopathologic analysis with the aid of immunohistochemistry (IHC) and/or flow cytometry immunophenotypic analysis. MALT lymphoma represents a progression from a persistent chronic inflammatory process, and therefore distinguishing MALT lymphoma from chronic inflammation by histopathology may be challenging in some cases. Despite recent trends to consider IGH rearrangement/clonality as a confirmatory diagnostic test of MALT lymphoma, this method is far from ideal for this purpose since a positive or a negative result does not necessarily confirm or exclude that a process is lymphoma or reactive. This test must be correlated with the morphologic findings. Moreover, MALT lymphoma may arise in association with underlying autoimmune conditions where clonal lymphoid populations are not uncommonly detected. Therefore, we believe that an integrated approach including detailed morphologic review in combination with IHC and/or flow cytometry is best to establish a diagnosis of MALT lymphoma in most cases. We present helpful morphologic tips to avoid potential diagnostic pitfalls at some of the most common extranodal sites, including the stomach, ocular adnexa/conjunctiva, salivary gland, lung, thymus, breast, thyroid, small and large intestine and the dura. The differential diagnosis of MALT lymphoma with IgG4-related disease is also discussed., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Chronic lymphocytic leukemia (CLL) is an indolent low-grade B-cell neoplasm that generally responds well to treatment. Rarely, CLL cases exhibit an IGH::CCND1 rearrangement, presenting a diagnostic challenge in distinguishing between clonal evolution within CLL and an independent mantle cell lymphoma. We report a case of CLL with the emergence of an IGH::CCND1 rearrangement and mutations associated with treatment resistance, including TP53, BTK, and BCL2, during disease progression. Immunophenotypic, cytogenetic, and molecular analyses support that these alterations are secondary events within the CLL clone. This case demonstrates dynamic clonal selection and expansion in response to treatments, which, in turn, contributes to treatment resistance., Competing Interests: The authors declare no conflict of interest., (© 2024 The Author(s). eJHaem published by British Society for Haematology and John Wiley & Sons Ltd.)

Phyllodes tumor of the breast is an infrequently encountered fibroepithelial neoplasm, which accounts for 0.3-1% of all tumors. Few case reports have described the occurrence of giant phyllodes tumor. To our knowledge, about 20% of phyllodes tumors would be considered giant benign. Complete surgical excision is the standard of care for giant benign phyllodes tumors; axillary lymph node metastasis is rare, and dissection should be limited to patients with pathologic evidence of tumor in the lymph nodes. We report the case of a 40-year-old Mexican woman with giant mammary tumor who underwent a right total mastectomy. The pathology results showed a benign phyllodes tumor 4,857 g in weight and 40.2 × 36.3 × 15 cm in size. We do not suggest adjuvant radiation therapy for patients with benign phyllodes tumors that are widely excised. A review of the pertinent literature was performed., Competing Interests: The authors have no conflicts of interest to declare., (Copyright © 2021 by S. Karger AG, Basel.)

Eccrine porocarcinoma (EPC) is an infrequent cutaneous neoplasm, and was described in 1963 by Pinkus and Mehregan. It is a rare type of skin tumor (0.005-0.01% of all skin tumors). Less than 300 cases have been described in the entire world medical literature. To our knowledge, no case of intergluteal cleft EPC has been reported in the literature in English and Spanish to date, so this would be the first reported case of such pathology. Metastatic EPC is less frequent, since only <10% of metastatic type have been reported and the rest as localized disease. The primary treatment of choice is surgical wide local excision of the tumor with histological confirmation of tumor-free margins. Prognosis is difficult to determine because of the rarity of EPC and the variations in natural history. There are no data to support the use of adjuvant chemotherapy or radiotherapy, and there are currently no agreed criteria to define patients at high risk of relapse. We present a 67-year-old man with intergluteal cleft eccrine tumor by biopsy. Metastasis to left inguinal region and lung was reported by contrasted abdominal and chest computed tomography. He started chemotherapy based on etoposide, vincristine, carboplatin. A review of pertinent literature is provided., Competing Interests: The authors have no conflicts of interest to declare., (Copyright © 2020 by S. Karger AG, Basel.)