Cutaneous Syncytial Myoepithelioma: An Uncommon and Distinct Variant of Cutaneous Epithelioid Neoplasm.

BACKGROUND: Cutaneous syncytial myoepithelioma (CSM) is an uncommon and distinct variant of cutaneous myoepithelioma. We aim to present a case of CSM to enhance the recognition of this unique variant, encompassing its clinical characteristics, histopathological features, immunohistochemical staining, and therapeutic approaches. CASE PRESENTATION: A 10-year-old girl presented with a dome-shaped nodule located on the skin of her left medial distal arm. Microscopic examination of the skin biopsy revealed a well-defined dermal nodular lesion, surrounded by an epidermal collarette. Tumor cells were composed of epithelioid to spindle-shaped cells with round-to-oval nuclei, small nucleoli, and abundant eosinophilic cytoplasm with a syncytial-like growth pattern. A moderate degree of nuclear pleomorphism was noted. Mitotic activity was not prominent. Immunohistochemical staining revealed positive staining for epithelial membrane antigen, GLUT1, collagen IV, and S100. Smooth muscle actin, CD10, and CD68 showed patchy positivity. CD31, CD34, p63, SOX10, anaplastic lymphoma kinase (ALK), glial fibrillary acidic protein, pankeratin (AE1/AE3/PCK26), Melan-A, and CD1a were negative. Fluorescence in situ hybridization targeting TFE3 and ALK genes was negative. The differential diagnosis included ALK-negative epithelioid cell histiocytoma, epithelioid perineurioma, and CSM. Based on the above findings, a diagnosis of CSM was rendered. DISCUSSION: CSM is a benign cutaneous neoplasm composed of sheets of histiocytoid or short spindle cells with pale eosinophilic cytoplasm with a syncytial-like growth pattern. Clinically, CSM often presents as a painless, slow-growing nodule or plaque in a broad anatomical distribution with a preference for the distal extremities.. CSM is characteristically positive for epithelial membrane antigen (EMA) and S100 protein and negative for keratins. In challenging cases, molecular testing for EWSR1 gene rearrangement and EWSR1-PBX3 gene fusion aid in confirming the diagnosis. CONCLUSIONS: The histologic features of CSM present a unique set of challenges posing a diagnostic dilemma, as they can bear resemblance to a range of benign and malignant cutaneous neoplasms including ALK-negative epithelioid cell histiocytoma, epithelioid perineurioma, malignant or nevoid melanoma, and epithelioid sarcoma. An accurate diagnosis is crucial for guiding proper clinical management considering that this entity typically demonstrates an excellent prognosis following a complete surgical excision.

Lymphangitic Melanomatosis: Case Report of Intralymphatic Spread of Melanoma in a 66-year-old Man.

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.

Erythema Multiforme-Like Fixed Drug Eruption During Azathioprine and Hydroxychloroquine Treatment for Systemic Lupus Erythematosus Mimicking Rowell Syndrome: A Rare and Challenging Clinical Scenario.

Background. Fixed drug eruption and Rowell syndrome stand as intriguing entities with overlapping clinical and pathological features. Case Presentation. A 32-year-old female patient presented with a tender and pruritic rash on the left upper chest for 3 days. Clinical examination revealed a flaring rash on the chest, under her left eye, tongue, and lips. The patient had a significant past medical history of systemic lupus erythematous with positive (ANA, Sm, dsDNA, ribosomalP, RNP) antibodies, hypocomplementemia, inflammatory arthritis, discoid lupus, leukopenia, thrombocytopenia, and immune thrombocytopenic purpura, and avascular necrosis affecting both hips and her right knee. At the time of presentation, the patient was on azathioprine 150 mg daily and hydroxychloroquine 200 mg twice daily. Skin biopsy of the left upper chest revealed interface dermatitis with necrotic keratinocytes at the dermal-epidermal junction. Superficial and, in some areas, deep perivascular and peri adnexal lymphocytic infiltrates were observed, accompanied by eosinophils. CD123 staining highlighted 16% of the inflammatory cells. Direct Immunofluorescence for IgG, IgA, IgM, C3, and fibrinogen revealed positive linear basement membrane staining for IgG and fibrinogen, with no significant staining for the remaining immunoreactants. Considering the patient's history of medicine usage, and negative SS-A and SS-B antibody, a fixed drug eruption was favored. Discussion. This article discusses the clinical presentations, pathophysiological mechanisms, and diagnostic criteria for fixed drug eruption and Rowell syndrome. Conclusion. Awareness of the distinct clinical and histopathologic features of fixed drug eruption and Rowell syndrome, particularly when sharing cutaneous manifestations, underscores the importance of a comprehensive diagnostic approach and laboratory testing.

Myxoid neurofibroma masquerading as lymphatic-venous malformation and poses a diagnostic challenge on fine needle aspiration biopsy.

BACKGROUND: Myxoid neurofibromas (NF) are uncommon, benign spindle cell tumors that originate from peripheral nerve sheaths, often posing a diagnostic challenge due to their hypocellularity on cytology specimens. Distinguishing myxoid spindle cell lesions can be challenging, given the broad range of potential differential diagnoses. CASE PRESENTATION: A 26-year-old female with a past medical history of embolized inguinal, flank, and retroperitoneal venolymphatic malformation presented with a left pelvic pain causing significant disability. CT scan showed an extensive 8.7 cm × 6.6 cm retroperitoneal mass. FNA was performed and alcohol-fixed papanicolaou-stained smears showed a hypocellular specimen with loosely arranged clusters of bland spindle cell proliferation in the background of a mucoid matrix. Spindle cells showed scant cytoplasm and elongated oval-shaped regular nuclei. Prominent nucleoli were not seen. An excisional biopsy revealed a bland spindle cell proliferation in a myxoid background associated with shredded collagen bundles. Immunohistochemical staining showed diffuse positivity for S100 and CD34. Based on the overall findings, a definitive diagnosis of myxoid neurofibroma was rendered. DISCUSSION: Cytological features of myxoid neurofibroma include the presence of hypocellular spindle-shaped cells arranged in small, loosely organized groups within a myxoid matrix background. Cells exhibit scant cytoplasm with regular oval and elongated nuclei. Nucleoli are typically not identified. The differential diagnosis includes myxoid neurofibroma, myxoma, myxoid liposarcoma, myxoid chondrosarcoma, myxoid dermatofibrosarcoma protuberans, low-grade fibromyxoid sarcoma, and low-grade myxo-fibrosarcoma. CONCLUSION: We aim to highlight the importance of considering myxoid neurofibroma in the differential diagnosis of hypocellular myxoid spindle cell lesions encountered on fine-needle aspiration cytology.

Malignant Para-Testicular Mesothelioma: A Rare Presentation in the Tunica Vaginalis of an Elderly Male With No Prior Asbestos Exposure.

Malignant mesothelioma of the tunica vaginalis is an extremely rare and aggressive tumor that is frequently encountered in elderly patients. The diagnosis of malignant mesothelioma of the tunica vaginalis poses a diagnostic challenge due to its infrequency and nonspecific clinical presentation. Histopathological examination and immunohistochemical staining are essential in differentiating this tumor from other para-testicular masses and establishing a definitive diagnosis. Early detection and comprehensive treatment planning are crucial for improving the prognosis and overall outcomes for patients with this rare malignancy. We present a report of malignant mesothelioma of the tunica vaginalis in a 78-year-old male patient with no history of asbestos exposure who presented with a large infiltrative left para-testicular mass. Histopathological examination revealed a biphasic proliferation composed of epithelioid and spindle cells with infiltrative features, foci of necrosis, and increased mitotic figures. Immunohistochemical staining exhibited positive staining for WT1, D2-40, and calretinin, supporting the mesothelial origin of the tumor. Notably, BerEP4 staining was negative, arguing against carcinoma. Immunostaining for keratin 5 was positive, supporting the mesothelial differentiation. The Ki67 proliferation index was high. The differential diagnosis included adenomatoid tumors, germ cell tumors, and pleomorphic sarcoma. We aim to discuss the clinical presentation, diagnostic approach, and therapeutic approaches of this rare entity.

Extra-Ocular Sebaceous Carcinoma in Situ of the Arm of an Elder Male: An Unusual Presentation in an Atypical Location.

Background. Sebaceous carcinoma in situ outside the ocular region is an exceedingly uncommon. It is an intraepidermal neoplasm originating from sebaceous glands limited to the epidermis with no invasion into the underlying dermis or beyond. Although sebaceous carcinoma in situ is predominantly observed in ocular regions, particularly the eyelids, instances of its occurrence in extraocular locations are infrequent, with only a limited number of examples reported in the literature. Case Presentation. A 63-year-old man presented with a left posterior arm lesion. Microscopic examination revealed a proliferation of poorly differentiated atypical neoplastic sebocytes confined to the epidermis with pleomorphic nuclei, prominent nucleoli, and clear cell changes. The neoplastic cells demonstrated positive staining for adipophilin, androgen receptor, epithelial membrane antigen, P63, BerEP4, and keratin 7. Microsatellite instability markers showed preserved nuclear staining for MLH1, PMS2, MSH2, and MSH6. A definitive diagnosis of sebaceous carcinoma in situ was rendered. Discussion. The distinctive histopathologic characteristics typically involve the presence of atypical sebaceous cells confined within the epidermis. Atypical cells often exhibit enlarged nuclei, increased mitotic activity, and prominent nucleoli. A panel of epithelial membrane antigen, adipophilin, and androgen receptors is essential for ensuring an accurate diagnosis. Conclusion. This report underscores the importance of considering sebaceous carcinoma in situ in diagnosis in atypical locations, emphasizing the need for a comprehensive histopathologic examination and immunohistochemical staining panel. This article aims to demonstrate the rarity of sebaceous carcinoma in situ in extraocular sites to broaden our understanding of its diverse clinical presentations.

High-Grade Spindle Cell Sarcoma of the Scalp With an MGA::NUTM1 Gene Fusion in a Pediatric Patient.

ABSTRACT: NUT carcinoma (NC) is a rare and aggressive neoplasm associated with a poor prognosis. NC is characterized by a NUTM1- rearrangement on chromosome 15q14, commonly fused with the BRD4 or BRD3 gene . A rare subset of NC defined by fusion of NUTM1 with the MGA gene has been identified, showing mesenchymal differentiation on histology. Few cases of spindle cell sarcomas harboring MGA::NUTM1 gene fusions have been reported in the literature. We describe a case of spindle cell sarcoma harboring an MGA::NUTM1 fusion in a 6-year-old male patient. In contrast to typical cases of spindle cell carcinomas or NC, NUTM1 fusion-positive sarcomas are associated with a better prognosis. This report highlights the importance of diagnostic workup of undifferentiated neoplasms, as identification of the MGA::NUTM1 fusion in spindle cell sarcoma could be used in treatment algorithms and lead to better outcomes, to the benefit of patients.

Pseudoangiomatous Spindle Cell Lipoma: A Rare and Distinct Pattern of Lipomatous Tumors.

Pseudoangiomatous spindle cell lipoma is a rare pattern within the spindle cell lipoma spectrum that exhibits a remarkable histological pattern characterized by its resemblance to vascular lesions, creating a pseudoangiomatous appearance. Approximately 20 to 30 reports have been described in the literature. In this context, we present an intriguing report of pseudoangiomatous spindle cell lipoma showcasing a unique low-fat pseudo angiomatous pattern in a 61-year-old male patient presented with a 6-cm subcutaneous mass on his right arm, which was thoroughly investigated and subsequently excised. Microscopic examination revealed bland spindle cells infiltrates within a fibromyxoid stroma. Notably, the tumor exhibited distinctive branching and dilated vascular-like spaces that formed pseudopapillary (villiform) projections. Interestingly, the tumor displayed certain regions featuring mature adipose tissue components, alongside hyalinized blood vessels. No necrosis, atypical spindle cells, increased mitotic activity, or pleomorphic lipoblasts were observed. The immunohistochemical evaluation demonstrated diffuse positive staining for CD34 and negative staining for STAT6. This report of a low-fat pattern of pseudoangiomatous spindle cell lipoma underscores the importance of recognizing and characterizing rare entity subtype for accurate diagnosis and appropriate management. This report contributes to the expanding understanding of the diverse presentations of pseudo angiomatous spindle cell lipomas and underscores the significance of comprehensive histopathological assessment.