Kozyreva AA, Tsvetnov IV, Lyapichev KA
… +1 more, Haiduk II
Am J Dermatopathol
· 2026 May · PMID 41779629
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Primary cutaneous diffuse large B-cell lymphoma-leg type (PCDLBCL-LT) is a rare and aggressive lymphoma of elderly patients, typically affecting the lower extremities and characterized by centroblast- and immunoblast-lik...Primary cutaneous diffuse large B-cell lymphoma-leg type (PCDLBCL-LT) is a rare and aggressive lymphoma of elderly patients, typically affecting the lower extremities and characterized by centroblast- and immunoblast-like cells with a non-germinal center phenotype (MUM1+, BCL2+, IgM+, CD10-). CD5-positive cases are exceptionally uncommon and pose a diagnostic challenge, as CD5 expression broadens the differential diagnosis to include other B-cell lymphomas such as mantle cell lymphoma and transformed chronic lymphocytic leukemia. We describe a 70-year-old female patient who presented with a 2-cm cutaneous nodule on the lower extremity. Histopathology revealed a pandermal diffuse infiltrate of atypical large B-cells. Immunohistochemistry showed a CD5+, CD20+, MUM1+, BCL2+, IgM+, cyclin D1-profile, supporting CD5 + PCDLBCL-LT. Fluorescence in situ hybridization for MYC , BCL2 , and BCL6 rearrangements were negative, effectively ruling out double-hit/triple-hit lymphoma. The patient achieved a complete metabolic response after six cycles of R-CHOP chemotherapy, which was maintained for 24 months. However, she subsequently developed extracutaneous relapse involving the soft tissues of the extremities, trunk, and periorbital region, consistent with a progression. Treatment with a rituximab-bevacizumab combination regimen induced a second complete remission, sustained for six months at the time of reporting. Our case highlights the importance of routine CD5 testing in PCDLBCL-LT to identify this distinct subgroup and to guide appropriate differential diagnosis and patient monitoring.
Syringomatous tumor typically occurs in the nipple of female patients and is regarded as a breast-specific tumor rather than a cutaneous adnexal tumor, owing to its nipple location and its differentiation toward large br...Syringomatous tumor typically occurs in the nipple of female patients and is regarded as a breast-specific tumor rather than a cutaneous adnexal tumor, owing to its nipple location and its differentiation toward large breast ducts. Herein, we report the first axillary case of syringomatous tumor arising from supernumerary mammary tissue lacking a supernumerary nipple. A 25-year-old woman presented with a 7-mm nodule in the left axilla. Histopathologic examination revealed a poorly circumscribed tumor composed of small tubules embedded in abundant fibrosing stroma, extending from the mid-dermis to superficial subcutis. The tumor tubules demonstrated showed a 2-cell layer consisting of cuboidal glandular epithelial cells and flattened myoepithelial cells with minimal atypia. Keratinous cysts were scattered throughout the superficial portion of the tumor. Medium-sized ductal structures suggestive of mammary ducts were identified within and at the periphery of the tumor. Diffuse immunoexpression of cytokeratin 5/6, cytokeratin 7, and cytokeratin 19 was observed. Most tumor cells also expressed S100 protein, SOX10, and c-kit, whereas estrogen receptor positivity was limited in the tumor component. α-Smooth muscle actin and p63 highlighted the peripheral myoepithelial cell layer of the tumor tubules. This case demonstrates that syringomatous tumor can arise in supernumerary breast tissue lacking a nipple. Histopathologically, syringomatous tumor may resemble cutaneous adnexal tumors, particularly syringoma and microcystic adnexal carcinoma, and breast carcinomas. However, in addition to the clinical appearance and location, the presence of a peripheral myoepithelial lining and immunoexpression of SOX10 and c-kit may help exclude these entities.
Am J Dermatopathol
· 2026 Feb · PMID 41747151
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The rising incidence of melanoma highlights the limitations of traditional diagnostic methods, including inefficiency, subjectivity, and poor quantifiability. Consequently, deep learning (DL)-based diagnosis and prognosi...The rising incidence of melanoma highlights the limitations of traditional diagnostic methods, including inefficiency, subjectivity, and poor quantifiability. Consequently, deep learning (DL)-based diagnosis and prognosis using whole-slide images (WSIs) has emerged as a major research focus. This systematic review adhered to PRISMA guidelines to outline the current landscape and trends in this rapidly evolving field, analyzing relevant studies published between January 2020 and June 2024, retrieved from PubMed and Web of Science. After screening, 27 studies were included for qualitative synthesis. The review first details the application of DL in the diagnostic classification of melanoma WSIs, encompassing both binary and multiclass categorization. It further examines the emerging role of DL in prognostic assessment based on WSIs. Through a critical analysis of the included literature, key challenges are identified, primarily concerning the generalizability, interpretability, and clinical integration of these models. Finally, the article proposes targeted future research directions to address these barriers, aiming to guide the translation of DL tools from research to clinical practice and toward more precise management of patients with melanoma.
Diffuse dermal angiomatosis represents a reactive form of microvascular proliferation characteristically linked with vascular insufficiency of diverse etiology. It occurs most commonly on the lower extremity where a freq...Diffuse dermal angiomatosis represents a reactive form of microvascular proliferation characteristically linked with vascular insufficiency of diverse etiology. It occurs most commonly on the lower extremity where a frequent association is venous insufficiency; however, it can exhibit breast localization falling under the designation of diffuse dermal angiomatosis of the breast (DDAB). The clinical presentation of DDAB can be striking and resembles a catastrophic thrombogenic vasculopathy such as purpura fulminans, calciphylaxis, and antiphospholipid antibody syndrome. However, a less common presentation is one of diffuse erythema mimicking inflammatory breast carcinoma as the main clinical presentation. Most articles devoted to the topic of DDAB describe a reproducible association with diseases and/or other risk factors such as smoking that can result in microvascular insufficiency. In contradistinction, the development of this reactive vascular process in a healthy patient would be considered exceptionally uncommon, albeit it has been reported. We describe a case of bilateral DDAB in a patient who was 21 weeks pregnant; the clinical diagnosis was inflammatory breast carcinoma. The case was unusual for three primary reasons: the age of the patient, the lack of any history of vascular insufficiency, and the clinical presentation resembling inflammatory breast carcinoma. Although the downstream effects eventuated in dermal angiomatosis, the upstream mechanisms were clearly different than what is implicated in conventional DDAB. The pathophysiology as it applies to this case is explored. Our patient serves to expand the clinical and pathophysiologic spectrum of DDAB .
Hoang M, Mirza FN, Wang AR
… +4 more, DiMarco C, Hart J, Robinson-Bostom L, Libby TJ
Am J Dermatopathol
· 2026 May · PMID 41711635
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Superficial leiomyosarcoma is a rare soft tissue sarcoma that typically presents as a firm, painful nodule in adults older than 50 years. We report a unique case of a 35-year-old woman with a slow-growing, mobile, subcut...Superficial leiomyosarcoma is a rare soft tissue sarcoma that typically presents as a firm, painful nodule in adults older than 50 years. We report a unique case of a 35-year-old woman with a slow-growing, mobile, subcutaneous nodule on the upper arm, initially presumed to be a benign lesion, most likely an angiolipoma. After excisional biopsy, histopathologic evaluation revealed an intermediate-grade leiomyosarcoma with focal dedifferentiation, demonstrating an abrupt transition from well-differentiated leiomyosarcoma to a high-grade, immunophenotypically undifferentiated sarcoma. Immunohistochemical staining showed loss of smooth muscle actin and desmin in the central dedifferentiated region, with retention of these stains at the peripheral lower-grade components. Wide local excision achieved clear margins, and imaging revealed no metastasis. Only 2 prior cases of cutaneous dedifferentiated leiomyosarcoma have been reported, both in the head and neck and with a more classic clinical presentation of a firm and immobile nodule. Our case is unusual in its location and deceptively benign clinical presentation. Given its aggressive potential and high reported rates of metastasis and mortality, prompt recognition and excisional biopsy are essential for diagnosis. This case highlights the importance of maintaining clinical suspicion for malignancy in persistent subcutaneous nodules and adds to the limited literature on dedifferentiated cutaneous leiomyosarcoma.
Am J Dermatopathol
· 2026 Mar · PMID 41700579
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Recently, a number of clear cell neoplasms with melanocytic differentiation have been reported. A more recently described fraction of these are microphthalmia-associated transcription factor (MITF) fused neoplasms. We re...Recently, a number of clear cell neoplasms with melanocytic differentiation have been reported. A more recently described fraction of these are microphthalmia-associated transcription factor (MITF) fused neoplasms. We report an additional case of an ACTG1::MITF fusion clear cell neoplasm on the right lateral thigh of a 74-year-old woman with detailed immunophenotypic and molecular analysis. Thus far, only 12 prior cases of MITF fusion clear cell tumors with melanocytic differentiation have been reported in the literature, of which 9 had an "ACTIN" fusion partner. Hence, more studies are needed to fully characterize the immunophenotypic, molecular, and clinical features of these tumors. This tumor had strong nuclear staining with MITF, complete absence of SOX10 staining, and weak blush positivity of the cytoplasm with S100. Mart-1 and HMB-45 showed focal positive staining. Furthermore, we compare the clinical, morphologic, and immunophenotypic features of our case and other MITF fusion tumors with other morphologically similar tumors such as clear cell sarcoma, CRTC1::TRIM11 fused neoplasms, NONO::TFE3 epithelioid and spindle cell neoplasms, MED15::ATF fused neoplasms, and PEComas. Although all these tumors share a common theme of MITF pathway overactivation, there are distinct clinical, morphologic, and immunophenotypic differences. In addition to detailing specific features of our case, we also discuss those differences that may help distinguish ACTG1::MITF fusions from other clear cell tumors. Considering the significant differences in clinical outcomes between these distinct classes of clear cell tumors, accurate distinction can significantly affect management options.
Am J Dermatopathol
· 2026 Mar · PMID 41700578
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Papillary thyroid carcinoma is a well-differentiated cancer with a high cure rate after surgery. Metastases are rare, and typically involve cervical lymph nodes, lungs, or bone. Cutaneous metastases are much less common...Papillary thyroid carcinoma is a well-differentiated cancer with a high cure rate after surgery. Metastases are rare, and typically involve cervical lymph nodes, lungs, or bone. Cutaneous metastases are much less common and portend a poor prognosis because of widely disseminated disease. Although clinical presentation may vary, histopathology and immunohistochemistry are distinctive. Frequent locations of cutaneous metastases include the scalp, face, and neck. This case highlights an uncommon presentation of an isolated cutaneous papillary thyroid carcinoma metastasis in a young female patient.
Kiszluk A, Alhalaseh YN, Asar MC
… +2 more, Chen F, Speiser JJ
Am J Dermatopathol
· 2026 Mar · PMID 41700577
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Desmoplastic melanoma (DM) remains a challenging diagnosis. Because DM can resemble a scar on histopathology, evaluation of re-excision specimens may be particularly difficult due to the need to distinguish residual DM f...Desmoplastic melanoma (DM) remains a challenging diagnosis. Because DM can resemble a scar on histopathology, evaluation of re-excision specimens may be particularly difficult due to the need to distinguish residual DM from scar tissue formed during the initial biopsy, especially in markedly regressed or traumatized lesions. Although several immunohistochemical stains, including S100 and SOX10, have high sensitivity for DM, these stains are also positive in re-excision scars. Verhoeff-van Gieson (EVG) is a special stain that visualizes elastin fibers, but no studies to date have used EVG to compare the distribution of elastin in DM with that of scar tissue. We stained 17 DMs and 17 re-excision scars with EVG and found that 76% (13/17) of DMs demonstrated preservation of elastic fibers between melanocytes, while elastin was absent in 100% of scars. Two DMs, while negative for intratumoral elastin, showed layering of elastin at the base of the lesion. Another 2 DM specimens, from 88- and 92-year-old patients, respectively, were entirely devoid of elastin, perhaps due in part to natural age-related degenerative changes. In DMs that retain elastin between melanocytes, EVG may be useful in differentiating DM from scar. Caution should be exerted when specimens are negative for intratumoral elastin, particularly in older patients and when excision is significantly delayed, as regeneration of elastin fibers has previously been shown to begin 3 months after biopsy.
Am J Dermatopathol
· 2026 Mar · PMID 41700576
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The diagnosis of dermatologic conditions typically hinges on the examination of visibly apparent skin abnormalities. On occasion, dermatologists can aid in diagnosing the "invisible" by performing biopsies of skin that s...The diagnosis of dermatologic conditions typically hinges on the examination of visibly apparent skin abnormalities. On occasion, dermatologists can aid in diagnosing the "invisible" by performing biopsies of skin that seems clinically normal, with the hope that histologic clues only apparent in tissue samples-and not by the naked eye-may yield helpful diagnostic information. This narrative review discusses the utility of random, normal skin biopsy in the diagnosis of a variety of conditions for which this method has been described. Herein, we review the available literature on the use of normal skin biopsy for Alport syndrome, amyloidosis, atypical hemolytic uremic syndrome; cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, intravascular lymphoma, lysosomal storage disorders, pseudoxanthoma elasticum, rabies, and small fiber neuropathies.
Noebel C, Juillé ML, Gebing AM
… +2 more, Kazakov DV, Kervarrec T
Am J Dermatopathol
· 2026 May · PMID 41687124
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Poroma is a benign sweat gland tumor harboring YAP1::MAML2 and YAP1::NUTM1 fusion transcripts in most of the cases. Recently, YAP1 fusions have also been detected in trichoblastomas and in 1 sebaceoma. To expand the spec...Poroma is a benign sweat gland tumor harboring YAP1::MAML2 and YAP1::NUTM1 fusion transcripts in most of the cases. Recently, YAP1 fusions have also been detected in trichoblastomas and in 1 sebaceoma. To expand the spectrum of YAP1 -fused adnexal tumors, we report herein 2 cases of adnexal tumors with YAP1::MAML2 fusion transcript combining a poroma and a sebaceous component. These 10- and 7-mm diameter neoplasms arose in a 55-year-old man and in a 90-year-old woman and were located on the back and the right breast, respectively. Microscopically, both lesions harbored a biphasic appearance resulted from a superficial poroma component associated with relatively well-demarcated areas of sebaceous differentiation located either in the epidermal (case #1) or in the intradermal part of the lesions (case #2). Immunohistochemical investigation of the cases revealed diffuse positivity of the androgen receptor in the sebaceous areas together with loss of YAP1 in both poroid and sebaceous parts. Accordingly, molecular analysis of the cases revealed the presence of an in-frame YAP1::MAML2 fusion transcript. To conclude, our cases confirmed that YAP1 fusions are the oncogenic drivers of a subset of adnexal tumors that may harbor poroid, follicular but also sebaceous differentiation.