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Competing Interests: The authors declare no conflicts of interest.

Competing Interests: The authors declare no conflicts of interest.

Abstract: Melanoma with lymphatic invasion has been associated with increased risk of metastasis, but the mechanisms and clinical implications are poorly understood. Although current reports have documented angiotropic spread of melanoma and suggest lymphatic spread of melanoma to increase the likelihood of metastasis, to our knowledge, lymphangitic metastatic melanoma resembling cutaneous carcinomatosis or presenting with facial hyperpigmentation has not been described. In this case report, we describe extensive cutaneous intralymphatic spread of melanoma, or lymphangitic melanomatosis, producing macular skin pigmentation in a 66-year-old man., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Competing Interests: M. Gosch, A. Niehaus, and O. P. Sangüeza: No conflicts of interest.

Competing Interests: M. Gosch, A. Niehaus, and O. P. Sangüeza: No conflicts of interest.

Abstract: Mucinous syringometaplasia is a rare and poorly recognized entity that usually presents as a warty tumor in acral regions. It is more frequent in men, and the age of presentation is variable. Typically, it has been reported as a solitary lesion with a warty appearance that occasionally can drain serous material. The affected sites include head, neck, breast, acral regions, and buttocks. The evolution over time is variable. The pathogenesis has not been elucidated. Diagnosis is established through histopathology, the characteristic feature is an epidermal invagination, which creates a structure similar to a "pore" at the dermal level. The clinical differential diagnosis is mainly with a viral wart, but it can also resemble basal cell carcinomas and other adnexal tumors. The treatment is surgical, and no recurrences have been reported to date. We describe the case of a 25-year-old woman who presented with a lesion on one of her eyelids. A shave removal of the lesion was performed, and the diagnosis was established by histopathologic examination., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Competing Interests: The authors declare no conflicts of interest.

Competing Interests: The authors declare no conflicts of interest.

Keloidal morphea is a rare variant of scleroderma, which often can be clinically confused with keloid or scar formation. We report a 34-year-old woman with a medical history of asthma and Raynaud's phenomenon, presented for the evaluation and management of multiple erythematous hyperpigmented annular plaques reportedly developed after taking trimethoprim/sulfamethoxazole. An initial skin biopsy showed findings supportive of a drug eruption. She was treated with oral prednisone and achieved some improvement. She presented 1 year later with enlargement of the plaques and emergence of new lesions. Skin biopsies revealed an unremarkable epidermis with marked fibrosis of the mid-to-deep dermis with sparing of the papillary dermis, and superficial and deep perivascular and perieccrine lymphoplasmacytic inflammation. Verhoeff-Van Gieson staining demonstrated the loss of elastin fibers within the fibrotic areas of the biopsy specimens, which supported the diagnosis of keloidal morphea. Her laboratory tests were positive for antinuclear antibody (greater than 1:1280). She continued treatment with oral prednisone and topical steroids, and she showed improvement. This case highlights the importance of differentiating keloidal scleroderma from a hypertrophic scar or keloid to reveal an underlying systemic process. A correlation of clinical and histopathological findings is paramount to reach a correct diagnosis, ensure appropriate treatment, and monitor for comorbid disease.

Lichen planus (LP) is an idiopathic inflammatory disease of the skin, hair, nails, and mucous membranes. Classic cutaneous LP is characterized by violaceous flat-topped papules that typically favor the extremities. LP on the scalp, otherwise known as lichen planopilaris, classically presents with scarring alopecia, perifollicular erythema and follicular prominence. Although LP pigmentosus presents primarily as hyperpigmentation, there is only one previous report of hypopigmented LP. In this report, the authors report 2 cases of LP that presented primarily as hypopigmented macules in 2 African American men. The first patient presented with hypopigmented macules on face and scalp as well as trunk and extremities. The second patient presented with hypopigmented macules on scalp with associated alopecia. Histopathological examination from both patients showed features of LP. The authors propose a new variant of LP that presents acutely as hypopigmented lesions.

Melanocytic nevi located on specific regions of the body can demonstrate unusual histopathological features such as asymmetry, irregular nesting patterns, pagetoid spread, cytologic atypia, and rarely, mitotic activity. However, despite these features that may raise concern for malignant melanoma, these lesions follow a benign clinical course and do not require intervention. Also known as nevi of special sites or nevi with site-related atypia, these melanocytic nevi were initially described on acral sites and genitalia. Now, additional anatomical sites with known site-related atypia include the ear, conjunctivae, scalp, breast, flexural skin, legs, and back and shoulder. This continuing medical education article presents a review of the histopathological characteristics of special site nevi based on anatomic location. It is imperative for dermatologists, pathologists, and dermatopathologists to distinguish benign melanocytic nevi with site-related atypia from malignant melanoma to avoid unnecessary surgical intervention or treatment.

Tumor of follicular infundibulum (TFI) is currently believed to be a benign epithelial neoplasm with follicular differentiation. It has been suggested that TFI is associated with dermal scarring, but further investigation is needed to confirm this correlation. To approach this question, a retrospective study was presented, a total of 67 cases (64 lesions) were found in a search covering cases over a 10-year period. Overall, the presence of histological dermal scarring was noted in 34 of 64 (53.13%) cases. Of the cases where TFI was an incidental finding, the presence of dermal scarring was noted in 13 of 18 (72.22%) cases. Meanwhile, of the cases where TFI was the main diagnosis, the presence of dermal scarring was noted in 12 of 34 (35.29%) cases. This suggests that TFI may, in some cases, represent an epidermal reaction pattern to dermal scarring.

Mycosis fungoides (MF) is the most common primary cutaneous T-cell lymphoma. Although it was first described in 1833, our understanding of this disease has continued to evolve. From a diagnostic perspective, the diagnosis of MF can be challenging particularly in the early stages of the disease, because of overlap between the histological features of early MF lesions and many other inflammatory dermatoses. Furthermore, there has been an emergence of numerous clinicopathologic and immunohistochemical variants of MF reported in the literature. Although the prognostic significance of some of the rare variants is still not fully understood, certain variants, such as folliculotropic and bullous MF, have demonstrated less indolent clinical courses compared with classic MF and necessitate aggressive therapeutic measures. Thus, it is important for dermatologists and dermatopathologists to be knowledgeable of the widely varied clinical, histological, and immunohistochemical presentations of MF to arrive at a prompt and accurate diagnosis and initiate appropriate treatment.

We present the case of a 17-year-old male kidney transplant recipient who presented initially with dermatologic symptoms and was found to have histologic changes in the skin that were consistent with mycosis fungoides. Shortly after this diagnosis was made, imaging studies demonstrated multifocal interstitial and airspace consolidation in both lungs. Physical examination revealed no lymphadenopathy or hepatosplenomegaly, but an open lung biopsy revealed an Epstein-Barr virus (EBV)-negative monomorphic T-cell posttransplant lymphoproliferative disorder (PTLD) with a concomitant EBV-positive B-cell PTLD involving the same lesion of the lung. Polymerase chain reaction analysis demonstrated clonal T-cell receptor gene rearrangements in both the skin and the lung biopsies. Interestingly, 1 clone was shared between the skin and lung while a second clone was present only in the lung. To our knowledge, this is the first reported case of a PTLD presenting in the skin in which there was a subsequent discovery of composite, bilineal B- and T-cell PTLD of the lung.

Dermatofibromas are fibrohistiocytic lesions with numerous histologic variants. Ossifying dermatofibroma with osteoclast-like giant cells is an uncommon variant that has only rarely been reported. We report another case of ossifying dermatofibroma with osteoclast-like giant cells and describe the immunohistochemical expression pattern of these rare lesions. A 72-year-old male presented with a 3.5-cm subcutaneous nodule on the posterior right shoulder of several years duration. The excision specimen showed a large, dermal-based, well-circumscribed, nonencapsulated heterogenous spindle cell proliferation. Large islands of spindled cells arranged in a storiform pattern were separated by broad fibrous bands. Collections of multinucleated giant cells were present predominantly at the periphery of the spindle cell islands. In addition, small islands of bone with osteoblastic rimming were present multifocally, concentrated in the central portion of the lesion. The spindle cells express factor XIIIA, smooth muscle actin, and CD68 on immunohistochemical stains, confirming a fibrohistiocytic origin. There was no immunohistochemical expression for S100 protein, panmel, CD57, cytokeratin, neuron-specific enolase, or CD34. A broad differential diagnosis, including variants of melanoma and osteosarcoma, should be considered when analyzing cutaneous lesions with a fibrohistiocytic component admixed with giant cells and metaplastic bone.

Intralymphatic histiocytosis is a rare condition characterized by the presence of dilated lymphatic vessels containing aggregates of mononuclear histiocytes (macrophages) within their lumina. The phenomenon seems to occur almost exclusively within the reticular dermis. Although its pathogenesis remains uncertain, there has been speculation about the possible relationship between intralymphatic histiocytosis and intravascular reactive angioendotheliomatosis. In addition, several examples historically have been associated with rheumatoid arthritis. We describe our experience with 16 cases of intralymphatic histiocytosis. Clinically, the lesions were located predominantly on the upper and lower limbs, and they consisted of asymptomatic and poorly demarcated erythematous plaques and livedo reticularis-like lesions. They were characterized histopathologically by dilated vascular structures involving the reticular dermis. Some of these dilated vessels had empty lumina, whereas others contained variable number of mononuclear histiocytes. An inflammatory response of variable intensity from case to case was also present in the adjacent dermis. The dilated vessels exhibited thin walls with irregular shapes, and a single discontinuous layer of flat endothelial cells lined their lumina. Immunohistochemically, the endothelial cells lining the dilated lumina expressed immunoreactivity for CD31, CD34, podoplanin, D2-40, Lyve-1, and Prox-1, which confirmed their nature as lymphatic endothelial cells. Intralymphatic mononuclear histiocytes expressed CD68 (PGM1), although some cases also had variable immunoexpression for myeloperoxidase, CD31, and podoplanin. In the 4 cases that employed double immunohistochemistry, with podoplanin + CD68 (PGM1) or with Lyve-1 + CD68 (PGM1), each marker highlighted their specific target cells unequivocally; the endothelial cells expressed podoplanin or Lyve-1 immunoreactivity, and intralymphatic histiocytes showed CD68 (PGM1) immunoexpression. Our findings expand on the previously described morphologic and immunohistochemical features of intravascular histiocytosis. We also discuss the possible relationship between intralymphatic histiocytosis and the so-called reactive intravascular angioendotheliomatosis.

Ossifying plexiform tumor is a cutaneous lesion that microscopically resembles cellular neurothekeoma but has abundant central ossification as the prominent feature and has only been previously described in a single case report. We detail 2 additional examples, both arising on the finger of adult women (36 and 76 years old). Clinically, the lesions were described as a raised flesh-colored "extraosseous" mass, averaging 1.1 cm in greatest dimension. Histological examination showed an unencapsulated well-delineated dermal tumor with thin fibrous bands separating lobules and fascicles of epithelioid to spindled cells that were embedded in a somewhat loose myxoid matrix. Present within the center of the lobules were large irregular foci of mature bone, some lined by osteoblasts. After excision, these lesions have not recurred or persisted in a limited follow-up duration (9 and 2 months). In concordance with the only other case report of a 30-year-old woman with a left thumb mass, ossifying plexiform tumor has occurred exclusively on the digits of adult women. Although it is possible that ossifying plexiform tumor could represent an ossifying variant of cellular neurothekeoma, we believe it is a lesion sui generis, and hope its recognition will allow for an accurate diagnosis and distinction from other cutaneous ossifying lesions.

Cutaneous epithelioid angiomatous nodule is a peculiar and recently recognized vascular proliferation. Clinically, these lesions affect different areas of the body and histologically are characterized by a well-circumscribed, mainly unilobular, solid proliferation of endothelial cells with prominent epithelioid features. The cytoplasm is abundant and eosinophilic, and many of the neoplastic cells contain prominent vacuoles. Inflammatory infiltrates are variable. All the cases reported thus far have followed a benign course. We report 10 additional cases of this curious entity, including 2 which presented in an eruptive fashion and 5 that were located on the head and neck. We also discuss the histological differential diagnoses with other epithelioid proliferations and propose categorization within the spectrum of epithelioid hemangioma.

We report the case of a newborn with Langerhans cell histiocytosis involving the skin and multiple bones. All lesions resolved without therapy. This case underscores the benefits of a conservative approach in the absence of risk organ involvement.

Nephrogenic systemic fibrosis (NSF), also known as nephrogenic fibrosing dermopathy (NFD), occurs in renal failure patients after gadolinium contrast exposure. The fibrosis of the dermis and subcutaneous septae accompanies fibrosis of other organs, including the heart, liver, lungs, and muscle. The fibrotic skin demonstrates increased dermal collagen, fibroblasts, and mucin. The mechanism by which gadolinium is associated with fibrosis is not known. We tested the hypothesis that upregulation of transglutaminases contributes to the fibrosis seen in the organs, including skin, of renal failure patients exposed to gadolinium contrast. We performed immunohistochemical studies using antibodies to transglutaminase-2, factor XIIIa, transglutaminase isopeptide, and the histiocyte marker CD68 on five archived skin biopsies of NSF. The results indicate that the dermal fibroblasts and histiocytes of NSF express transglutaminase-2, CD68, factor XIIIa, and transglutaminase isopeptide, indicating increased expression and/or activation of transglutaminases in NSF. We recommend further research into the use of transglutaminase inhibitors in the treatment and prevention of NSF.

Pseudosclerodermatous panniculitis is an unusual variant of panniculitis that results as a complication of megavoltage radiotherapy. Four women developed this unusual entity on the anterior chest and abdominal skin after receiving megavoltage therapy for either breast carcinoma or painful bone metastases from breast carcinoma. Histopathologically, the epidermis and dermis of the involved area showed little or no evidence of radiodermatitis. The main findings were confined to the subcutaneous tissue and consisted of thickened, sclerotic septa composed of both thick and thin collagen bundles, and a lobular panniculitis characterized by lipophagic granulomas and scattered lymphocytes and plasma cells. Additionally, one of the cases showed markedly dilated vascular spaces with the appearance of lymphatics in the upper part of the dermis. Pseudosclerodermatous panniculitis after irradiation is an unusual cutaneous complication of megavoltage radiotherapy that should be distinguished from subcutaneous metastatic disease, cellulitis, or connective tissue diseases involving the subcutaneous fat. The differential diagnosis can be established on the basis of the characteristic histopathologic features of postirradiation pseudosclerodermatous panniculitis.

Malignant peripheral nerve sheath tumors (MPNSTs) encompass a wide and unusual group of neoplasms with features of neural differentiation. They most commonly present as spindle cell neoplasms and it can be difficult to differentiate them from other spindle cell neoplasms such as leiomyosarcomas, fibrosarcomas and synovial sarcomas. Strict criteria need to be applied in order to make the diagnosis of MPNSTs. Helpful features include contiguity with a nerve or an association with von Recklinghausen disease. The use of immunohistochemical stains may also help to confirm the diagnosis. Markers such as S-100 protein, neurofilament, epithelial membrane antigen and Leu-7 (CD57) are frequently used to assess neural differentiation in these neoplasms. In addition to the spindle cell pattern, MPNSTs may also display an epithelioid pattern. Rarely, other elements may be seen including glands in the so-called glandular MPNST or muscle in triton tumors. In more unusual cases cartilage, adipose tissue and even bone are present. Also included in the group of MPNSTs are the peripheral neuroepithelial tumor, neurotropic or desmoplastic melanomas and malignant granular cell tumors. MPNSTs are highly aggressive tumors and should be treated accordingly.

Erythema elevatum diutinum (EED) is a rare cutaneous condition that initially presents as leukocytoclastic vasculitis (LCCV) of the skin and later resolves with fibrosis. In addition to the LCCV, EED may show features reminiscent of other entities. For example, it may mimic lesions of dermatofibroma, granuloma annulare, granuloma faciale, or dermatitis herpetiformis. For this study, we reviewed the clinical records and 13 skin biopsies in eight patients with EED. One of the patients had concurrent pityriasis rubra pilaris, and another developed lesions of EED following and at the sites of mosquito bites; these associations have not been noted previously. In addition to such typical histopathological features as diffuse dermal involvement by neutrophils, eosinophils, and leukocytoclastic vasculitis, we also found two unusual patterns. The first was characterized by palisaded necrotizing granulomas, as previously described and associated with Churg-Strauss granuloma; the second condition simulated a pyogenicgranuloma--like lesion.