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BACKGROUND: Histopathologic criteria for diagnosis of cutaneous mastocytosis include 20 mast cells per high-power field or clusters of 15 mast cells. We aimed to determine the specificity of these criteria for cutaneous mastocytosis in comparison with inflammatory disorders of mast cell activation. METHODS: Twenty-six cases of spongiotic dermatitis or urticaria were identified from 2021 to 2022. Recuts were stained with mast cell tryptase and slides were reviewed for the presence of 20 mast cells per high-power field and for clusters of 15 mast cells. In addition, seven cases of mastocytosis were reviewed for the same criteria. RESULTS: Twelve of 26 cases (46.1%) of spongiotic dermatitis/urticaria had at least 20 mast cells per high-power field. Three of 26 cases (11.5%) of spongiotic dermatitis/urticaria had a cluster of 15 mast cells. Six of seven cases (85.7%) of mastocytosis had at least 20 mast cells per high-power field; four of seven cases (57.1%) of mastocytosis had a cluster of 15 mast cells. CONCLUSIONS: In our study, the finding of 20 mast cells per high-power field was nonspecific as a single criterion for cutaneous mastocytosis. The finding of clusters of 15 mast cells was more specific but not sensitive.

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Desmoplastic trichilemmoma, an uncommon variant of trichilemmoma, is a benign adnexal neoplasm originating from the outer root sheath of a hair follicle, which has rarely been associated with atypical basaloid proliferations, including basal cell carcinoma. In this patient case, a 67-year-old female presented to our dermatology clinic for a skin check. On physical examination, a pearly, pink papule was noted on the vertex scalp, and a biopsy was obtained to rule out malignancy. Histologic examination of the lesion favored a desmoplastic trichilemmoma; however, a basaloid neoplasm could not be ruled out. Subsequently, the patient underwent Mohs micrographic surgery, and upon examination of the Stage I Mohs slides, superficial basal cell carcinoma was identified within the lesion. This case serves to further strengthen the known association between basal cell carcinoma and desmoplastic trichilemmoma. In addition, it demonstrates that the presence of basal cell carcinoma may not be observed on the initial biopsy of these lesions, underscoring the utility of complete surgical excision.

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BACKGROUND: Benign lichenoid keratosis (BLK) is a cutaneous lesion that can clinically mimic malignancy and may represent regression of a pre-existing lesion. BLK may show epidermal pseudo-nests prompting evaluation for a melanocytic lesion. False positivity of MART-1/Melan-A immunostaining in pseudonests has been showed; however, the value of SRY-related HMG-box 10 (SOX10) staining in BLK with features suspicious for a melanocytic proliferation has not been previously reported. METHODS: Twenty-one cases of BLK from 2015 to 2020 were identified. Slides were reviewed and SOX10 immunohistochemistry was performed on each case. Subsequently, Melan-A immunohistochemical staining was performed on all cases. RESULTS: In 10 cases (47.6%), unexpected SOX10 staining was seen in rare to numerous small, single cells in the epidermis above the basal cell layer. No malignancy was identified. Of the 10 cases, 8 (80%) showed suprabasal SOX10 staining did not show similar suprabasal Melan-A staining; 2 (20%) cases showed scattered suprabasal cells positive for Melan-A. CONCLUSION: SOX10 immunostaining in BLK can highlight scattered cells in the epidermis (not easily noticeable on routine stain). Performing SOX10 immunostain alone on BLK can prompt a misdiagnosis of a melanocytic lesion and should be done with caution.

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A patient presented with fever, generalised rash, confusion, orofacial movements and myoclonus after receiving the first dose of mRNA-1273 vaccine from Moderna. MRI was unremarkable while cerebrospinal fluid showed leucocytosis with lymphocyte predominance and hyperproteinorrachia. The skin evidenced red, non-scaly, oedematous papules coalescing into plaques with scattered non-follicular pustules. Skin biopsy was consistent with a neutrophilic dermatosis. The patient fulfilled the criteria for Sweet syndrome. A thorough evaluation ruled out alternative infectious, autoimmune or malignant aetiologies, and all manifestations resolved with glucocorticoids. While we cannot prove causality, there was a temporal correlation between the vaccination and the clinical findings.

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Hidrocystomas are benign cysts of sweat duct epithelium that can present as single or multiple lesions, with or without pigmentation. The size is typically 1-3mm in diameter. Although hidrocystomas commonly occur in most parts of the head and neck region, occurrence on the scalp is rare. Herein, we present a 29-year-old woman with a giant pigmented apocrine hidrocystoma of the scalp, which, to our knowledge, represents the largest of its kind reported to date.

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Spiradenoma is a benign cutaneous adnexal neoplasm that characteristically presents as a painful dermal nodule, often on the head or trunk. It has a distinct histologic phenotype and management involves surgical excision with low risk of recurrence. In comparison, adenoid cystic carcinoma (ACC) is a low-grade malignancy manifesting as an often painless subcutaneous mass with potential for local invasion, perineural extension, and high rates of recurrence after excision. We report the case of a 63-year-old male patient with a recurrent, painful hematoma-like cyst overlying the left lower extremity tibial tuberosity. A firm nodule was located at the base of the cyst, which was histologically consistent with spiradenoma. Interestingly, the lesion contained multifocal ACC-like components composed of epithelial basaloid cells surrounding pseudocystic structures filled with mucinous material. The ACC-like components did not demonstrate infiltration or perineural invasion. To the best of our knowledge, this is the second publication in the English literature regarding spiradenoma with an ACC-like pattern. Although a benign entity, knowledge of this morphological variant of spiradenoma is essential for diagnostic accuracy in these cases. If a limited biopsy captures only the ACC-like component of a spiradenoma, the lesion may be incorrectly diagnosed as ACC.

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We report the use of voriconazole troughs to achieve appropriate therapeutic levels in treatment of a cutaneous Scedosporium apiospermum infection. Following heart transplantation, a 63-year-old immunocompromised patient presented with post-traumatic nodular lesions on his right shin. Pathology showed fungal yeasts with culture revealing Scedosporium apiospermum. According to therapeutic drug monitoring, initial voriconazole treatment was subtherapeutic requiring increased dosing until appropriate therapeutic trough levels were attained, and resolution of the fungal infection was achieved.

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Eruptaneous metastasis is an uncommon presentation of colorectal adenocarcinoma that can occur years after diagnosis of the primary cancer or manifest as the first sign of malignancy. It is essential to diagnose these metastases immediately, as this late-stage development carries a poor prognosis. The scalp is one of the less common sites for skin metastases and nodules may be mistaken for benign entities. In this case report, we report on the case of a 61-year-old woman with CREST syndrome who presented with a cutaneous metastasis to the scalp as the first sign ofcolorectal adenocarcinoma.

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Cutaneous carcinosarcoma (CCS) is an extraordinarily rare neoplasm with a biphasic morphological pattern exhibiting both epithelial and sarcomatoid components. Although its histogenesis and biological aspects remain poorly understood, previous studies have postulated that this tumor may arise from single cancer stem cells which subsequently differentiate into distinct tumor lineages. In this study, we explored a wide array of mutational hot spot regions, through high-depth next-generation sequencing of 47 cancer-associated genes in order to assess the mutational landscape of these tumors and investigate whether the epithelial and mesenchymal components shared the same genetic signatures. Results from this study confirm that despite their striking phenotypic differences, both elements of this infrequent tumor indeed share a common clonal origin. Additionally, CCS appears to embrace a heterogeneous spectrum with specific underlying molecular signatures correlating with the defining epithelial morphotype, with those carcinosarcomas exhibiting a squamous cell carcinoma epithelial component exhibiting diverse point mutations and deletions in the TP53 gene, and those with a basal cell carcinoma morphotype revealing a more complex mutational landscape involving several genes. Also, the fact that our findings involve several targetable gene pathways suggests that the underlying molecular events driving the pathogenesis of CCS may represent future potential targets for personalized therapies.

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BACKGROUND: The p27(KIP1) and p57(KIP2) proteins belong to the CIP/KIP family of cyclin-dependent kinase inhibitors involved in the growth arrest and cellular senescence. High levels of p27(KIP1) unexpectedly have been detected in invasive malignant melanomas (MM), whereas the role of p57(KIP2) in melanocytic lesions is unknown. We therefore chose to study the expression of p27(KIP1) and p57(KIP2) in melanocytic neoplasms. DESIGN: The expression of p27(KIP1) and p57(KIP2) were examined by immunohistochemistry in 40 melanocytic neoplasms and by Western blot analysis in cultured human melanocytes. RESULTS: Expression of both nuclear p27(KIP1) and p57(KIP2) (> 10% of cells with nuclear labeling) was observed in most cases with non-proliferating melanocytes (8/10, benign nevi and 9/10 DN, dysplastic nevi), but in only a few cases containing proliferating melanocytes (3/11 RN, recurrent nevi and 2/9 MM, melanoma) (p < 0.002). In proliferating melanocytes, there was an inverse correlation of nuclear expression of p27(KIP1) and p57(KIP2) in both RN (p27(KIP1) = 3/11 RN and p57(KIP2) = 8/11 RN) and MM (p27(KIP1) = 7/9 MM and p57(KIP2) = 2/9 MM) (p < 0.05). Western blot analysis detected p57(KIP2) only in proliferating melanocytes. p27(KIP1) was detected in both proliferating and senescent melanocytes. CONCLUSION: The difference in expression patterns of p27(KIP1) and p57(KIP2) in proliferating and senescent melanocytes suggests the interplay between these proteins may play a functional role in melanocytic tumorigenesis.

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Nephrogenic fibrosing dermopathy is a recently recognized skin disorder similar in appearance to scleromyxedema but without the systemic involvement. We describe a 14-year-old girl with new-onset systemic lupus erythematosus and acute lupus nephritis who developed on the lower extremities confluent hyperpigmented, woody, indurated plaques that contained groups of coalescing erythematous papules. Nephrogenic fibrosing dermopathy was diagnosed histologically. Possible etiologies are discussed.

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Collagenomas are considered to be connective tissue nevi composed predominantly of collagen. Collagenomas have been classified into 4 different entities: familial cutaneous collagenoma, the Shagreen patch of tuberous sclerosis, eruptive collagenoma, and other isolated collagenomas. We describe a patient with multiple collagenomas that appeared and multiplied during gestation and discuss the reported cases of collagenomas that have been linked to pregnancy.

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A subepitheal myofibroblastic (SMF) cell layer has been described in the colon, and referred to as pericryptal myofibroblastic cell layer. SMF cells have been shown to produce basement membrane proteins, including type IV collagen and laminin. The aim of this work was to determine the status of the SMF cell layer in Barrett's metaplasia (BM), with and without dysplasia, and compare that to the previously reported distribution of SMF in normal colon and colonic adenomas and carcinoma. Sections of formalin-fixed, paraffin-embedded biopsies from 6 colonic adenomas and 5 colonic adenocarcinomas, as well as 4 cases of BM without dysplasia, 4 with low grade dysplasia, 4 high grade dysplasia and 4 with invasive adenocarcinoma were immunohistochemically stained for alpha smooth muscle actin using the immunoperoxidase method. A continuous layer of SMF cells was present in all normal colonic tissue and adenomas but was absent in all colorectal adenocarcinomas. Surprisingly, none of the cases of BM with or without dysplasia or carcinoma showed an organized SMF cell layer. Unlike the colon, the SMF cell layer is absent in BM even without dysplasia. We hypothesize that lack of the SMF cell layer in BM may contribute to the quick progression to esophageal adenocarcinoma, which, unlike that in the colon, occurs before an exophytic lesion becomes evident.

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BACKGROUND: The rare desmoplastic and spindle cell variants of malignant melanoma exhibit histological and biochemical features suggestive of early Schwann cell differentiation. These features include a spindle-shaped morphology, neurotropism, and the expression of the low affinity nerve growth factor receptor (p75NGFR). METHODS: We evaluated by immunohistochemistry (using formalin-fixed, paraffin-embedded tissues) nine desmoplastic and three spindle cell melanomas for the expression of peripherin, p75NGFR, neural cell adhesion molecule (CD56/N-CAM), and growth-associated phosphoprotein-43 (GAP-43). Peripherin is expressed in the neural crest and in neurons, but not in cells committed to the Schwann cell lineage. p75NGFR and CD56/N-CAM also are expressed in early neural crest cells, but persist in unmyelinated and early premyelinating Schwann cells. GAP-43 is expressed in unmyelinated Schwann cells, but is downregulated in the later premyelinating to promyelinating stages of cells committed to the Schwann cell lineage. RESULTS: Peripherin was expressed in 7/12 (58%), p75NGFR in 4/12 (33%), and CD56/N-CAM in 6/12 (50%) of the desmoplastic and spindle cell melanomas. GAP-43 was not expressed (0%) in any of the 12 melanomas (chi2, p = 0.05). CONCLUSIONS: Desmoplastic and spindle cell melanomas express protein markers common to cells of the neural crest and to neurons similar to the immunophenotype previously reported for epithelioid cell melanomas. The expression of peripherin and the lack of expression of GAP-43 further define that these rare subtypes of melanoma do not recapitulate the later committed stages of Schwann cell differentiation.

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