Lymphomatoid Papulosis With T-cell Receptor-Gamma Delta Expression: A Clinicopathologic Case-series of 26 Patients of an Underrecognized Immunophenotypic Variant of Lymphomatoid Papulosis

Lymphomatoid papulosis (LyP) has several histopathologic presentations. LyP featuring gamma-delta (γδ) T-cell receptor expression may masquerade as and may be misdiagnosed as aggressive cutaneous T-cell lymphoma, particularly primary cutaneous γδ T-cell lymphoma (PCGDTL) or γδ mycosis fungoides. We performed a clinicopathologic analysis of the largest series of LyP featuring γδ T-cell expression. We identified 26 patients with a diagnosis of LyP with γδ T cells from our institutions, as well as through a comprehensive review of the literature, and characterized these cases. Most cases were treated with topical steroids or not treated at all. The majority of cases showed a CD4 - CD8 + phenotype and featured at least one cytotoxic marker. Histopathologic features included an intraepidermal or dermal infiltrate with large cells and frequent angiotropism. One case was initially misdiagnosed as PCGDTL, requiring further therapy. Our case series, the largest international cohort of γδ T cell predominant LyP cases, confirms marked clinicopathologic heterogeneity that may contribute to misdiagnosis, reasserting the need to identify classic clinical features, CD30 + T-cell components, and markers of cytotoxicity when dealing with this differential diagnosis. A limitation of this study includes somewhat limited follow-up, histologic, and immunophenotypic information for some cases.

Apocrine Hidrocystoma of the Nail: A Unique Case

ABSTRACT

Apocrine hidrocystomas are benign, cystic neoplastic lesions resulting from the apocrine secretory component of the sweat gland. They most commonly occur on the head and neck, with predilection to the periorbital area. Less frequent sites include the axilla, nipple, external auditory canal, foreskin, conjunctiva, lower lip, and fingers, among others. The authors report a unique case of a nail bed hidrocystoma in a 55-year-old woman, a site not previously described.

Myelodysplasia cutis masquerading as granulomatous dermatitis

Myelodysplastic syndromes (MDS) are a group of clonal hematopoietic neoplasms resulting from mutations in stem cells. They carry a risk of transformation to acute myeloid leukemia. Cutaneous manifestations of MDS, including myelodysplasia cutis or infiltration by MDS tumor cells, are rare, but significantly associated with increased risk of progression to high-grade myeloid tumors. The clinical and histopathologic differential diagnosis for myelodysplasia cutis includes interstitial granulomatous dermatitis (IGD), a reactive granulomatous dermatitis (RGD) associated with systemic diseases including rheumatologic diseases, and hematologic malignancy like MDS. We report a patient with MDS who presented with myelodysplasia cutis masquerading as IGD both in a clinical and histopathological manner.

A CD56- immunoblastoid variant of blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive malignant hematologic neoplasm arising from plasmacytoid dendritic cells. It is a very rare tumor that constitutes less than 0.1% of all hematologic malignancies. Most patients with BPDCN present clinically with cutaneous lesions as the first sign of disease. Immunophenotypic variability with aberrant marker profiles has been reported. We report a case of a transcription factor 4 (TCF-4) + BPDCN, with negative CD56 expression in an 85-year-old woman with multiple skin nodules. A punch biopsy revealed a diffuse, monomorphous, and non-epidermotropic cell infiltrate involving the entire dermis. The infiltrate was composed of intermediate-sized cells with immunoblastoid morphology, which is an unusual morphologic variant. The neoplastic cells were strongly positive for CD45 and co-expressed CD4, CD123, TCF-4, BCL-2, and CD10. The Ki-67 proliferative rate was very high (90%). Negative immunostains included CD56, an unusual finding in BPDCN. This case illustrates the challenges encountered in the diagnosis of this entity, particularly in unusual morphologic variants and phenotypes. The elucidation of molecular signatures and development of targeted therapies for its management have been recently introduced and differ from acute myeloid leukemias. Hence, accurate diagnosis of BPDCN is critical for dermatopathologists.

Spiradenoma With Adenoid Cystic Carcinoma-like Changes: A Case Series of This Rare Variant With a Potential Diagnostic Pitfall

Spiradenomas are benign cutaneous adnexal neoplasms with sweat gland differentiation that can manifest a broad spectrum of histomorphologic appearances. While they show a characteristic histopathologic phenotype and clinical management involves surgical excision with a low risk of recurrence, there have been unusual histopathologic variants of spiradenoma reported, including cases with adenoid cystic carcinoma (ACC)-like changes. Primary cutaneous ACC is a low-grade malignancy presenting as a subcutaneous mass with the potential for local invasion, perineural invasion, and high rates of local recurrence after excision. The diagnosis of spiradenomas with ACC-like features can be challenging, especially when only the ACC-like component is present for evaluation. A retrospective analysis of 21 cases of spiradenoma with ACC-like changes were obtained from large academic institutions, was performed, and summarized below. All cases showed background of conventional spiradenoma, and the ACC-like areas represented a component in all lesions. The percentage of ACC-like component ranged from 5% to 40% in all cases. The ACC-like component was multifocal and without pleomorphism, perineural and/or vascular invasion, necrosis, or increased mitotic activity. MYB translocation and protein expression was studied in 16 cases by fluorescence in situ hybridization, polymerase chain reaction, and immunohistochemistry. All studied cases were negative for MYB / NFIB , MYB L1, and MYB F by fluorescence in situ hybridization and polymerase chain reaction and 3 cases were positive for MYB expression by immunohistochemistry. Our study expands on spiradenomas with ACC-like features that ought to be considered in the differential diagnosis of cutaneous neoplasms such as primary cutaneous ACC. Our results indicate that a thorough histopathologic inspection and strict application of well-defined histologic criteria are necessary to support the diagnosis of this unusual histopathologic variant. These tumors can be difficult to diagnose, and awareness of their histomorphologic spectrum will facilitate definitive diagnosis and avoid misdiagnosis with other conditions.

PRAME Expression Is a Useful Tool in the Diagnosis of Primary and Metastatic Dedifferentiated and Undifferentiated Melanoma

Although mostly recognized in the metastatic setting dedifferentiated and undifferentiated melanomas are increasingly recognized as cutaneous and, less commonly, mucosal primary tumors. Their diagnosis is challenging and dependent on sampling and recognition of a conventional melanoma precursor and/or detection of a mutation in a conventional melanoma driver gene. PRAME immunohistochemistry has recently become an important ancillary tool in the separation of melanoma from benign nevi, but no comprehensive studies exist regarding its value in the detection of dedifferentiated and undifferentiated melanomas and their separation from atypical fibroxanthoma and pleomorphic dermal sarcoma, the main differential diagnoses on sun-damaged skin. After retrieval from archival files, we performed PRAME immunohistochemistry on 11 primary and 10 metastatic dedifferentiated and undifferentiated melanomas, 11 atypical fibroxanthomas, and 10 pleomorphic dermal sarcomas. Nuclear staining was assigned extent (ranging from 0 to 4 and reflecting the percentage of PRAME-positive tumor nuclei) and intensity scores (graded as absent, weak, moderate, and strong, with assigned scores ranging from 0 to 3) with combined scores ranging from 0 to 7. Both primary and metastatic dedifferentiated and undifferentiated melanomas showed strong and diffuse nuclear PRAME staining with median combined scores of 7. Strong and diffuse staining was also seen in all conventional melanoma precursors except for desmoplastic melanoma. In contrast, PRAME staining in atypical fibroxanthoma and pleomorphic dermal sarcoma was patchy and weak with median combined scores of 2. Our data emphasize the diagnostic utility of PRAME staining as a first screening tool in the detection and workup of dedifferentiated and undifferentiated melanomas, both in the primary and metastatic settings. PRAME immunohistochemistry is particularly helpful as it is also positive in tumors without a recognizable conventional melanoma precursor and in those associated with desmoplastic melanomas, where PRAME is typically found to be negative.

Widespread livedo racemosa

A 41-year-old woman with monoclonal gammopathy of undetermined significance presented with a 1-year history of livedo racemosa that started on one arm after receiving the Pfizer BioNTech COVID-19 vaccine. Her primary care physician initially thought it was a benign reaction to the COVID-19 vaccine as her symptoms were on the same arm as the site of injection. However, the livedo racemosa subsequently became more widespread after COVID-19 infection.

Expression of microRNAs and their target genes in melanomas originating from gynecologic sites

Melanomas from gynecologic sites (MOGS) are rare and have poor survival. MicroRNAs (miRs) regulate gene expression and are dysregulated in cancer. We hypothesized that MOGS would display unique miR and mRNA expression profiles. The miR and mRNA expression profile in RNA from formalin fixed, paraffin embedded vaginal melanomas (relative to vaginal mucosa) and vulvar melanomas (relative to cutaneous melanoma) were measured with the Nanostring Human miRNA assay and Tumor Signaling mRNA assay. Differential patterns of expression were identified for 21 miRs in vaginal and 47 miRs in vulvar melanoma (fold change >2, p<0.01). In vaginal melanoma, miR-145-5p (tumor suppressor targeting TLR4, NRAS) was downregulated and miR-106a-5p, miR-17-5p, miR-20b-5p (members of miR-17-92 cluster) were upregulated. In vulvar melanoma, known tumor suppressors miR-200b-3p and miR-200a-3p were downregulated, and miR-20a-5p and miR-19b-3p, from the miR-17-92 cluster, were upregulated. Pathway analysis showed an enrichment of "proteoglycans in cancer". Among differentially expressed mRNAs, topoisomerase IIα (TOP2A) was upregulated in both MOGS. Gene targets of dysregulated miRs were identified using publicly available databases and Pearson correlations. In vaginal melanoma, suppressor of cytokine signaling 3 (SOCS3) was downregulated, was a validated target of miR-19b-3p and miR-20a-5p and trended toward a significant inverse Pearson correlation with miR-19b-3p (p = 0.093). In vulvar melanoma, cyclin dependent kinase inhibitor 1A (CDKN1A) was downregulated, was the validated target of 22 upregulated miRs, and had a significant inverse Pearson correlation with miR-503-5p, miR-130a-3p, and miR-20a-5p (0.005 < p < 0.026). These findings support microRNAs as mediators of gene expression in MOGS.

Low-grade Hidradenocarcinomas: A Clinicopathologic Study of an Unusual Carcinoma That Can Mimic its Benign Counterpart

Hidradenocarcinomas are rare cutaneous adnexal malignancies with sweat gland differentiation that can show a broad spectrum of histomorphologic appearances, ranging from low to high grade. The diagnosis of low-grade hidradenocarcinoma can be challenging and may be mistaken for benign hidradenomas, especially on superficial and partial samples. We performed a retrospective analysis of 16 low-grade hidradenocarcinomas, obtained from 4 large academic institutions. All neoplasms presented clinically as nodular lesions that ranged in size from 1.5 to 6.0 cm. All patients were adults and their age ranged from 33 to 74 years of age. All cases shared features similar to hidradenomas in the surface and mid portion of the tumors and all tumors had 1 or more histomorphologic clues to malignancy, including the presence of an asymmetric and infiltrative growth pattern (especially at the base of the tumors), perineurial invasion, and a desmoplastic stromal reaction. In the tumors evaluated for immunohistochemistry, the tumor cells were positive for p63, EMA, AE1/AE3, MNF116, and CK7. Three patients underwent sentinel lymph node biopsy, and 2 cases showed metastatic disease to regional lymph nodes. All cases (including the 2 cases that had regional lymph node metastasis), showed no local recurrence or distant metastasis observed after a complete re-excision of the tumors (follow-up range from 6 to 72 mo). Our study highlights the salient clinical and histopathologic features of low-grade hidradenocarcinomas and emphasizes the potential diagnostic pitfalls in distinguishing this entity from other neoplasms. Our results indicate that a combination of thorough histopathologic inspection is necessary to support the diagnosis of this rare neoplasm. These tumors can be exceedingly difficult to diagnose and awareness of the subtle features of low-grade hidradenocarcinoma is of importance are as it remains a diagnostic challenge for practicing pathologists.

An update on viral-induced cutaneous lymphoproliferative disorders. CME Part I

Viral-induced cutaneous T-cell lymphomas are an uncommon group of lymphoproliferative disorders characterized by a viral infection of T and natural killer (NK) cells. This group of cutaneous T-cell lymphomas is more commonly encountered in Asians and Native Americans from Central and South America compared with Western populations. Viral-associated lymphoproliferative disorders include a spectrum of entities that range from nonneoplastic lesions, such as chronic active Epstein-Barr virus infection and infective dermatitis to malignant diseases, such as extranodal NK/T-cell lymphoma, hydroa vacciniforme-like T-cell lymphoma, and adult T-cell leukemia/lymphoma. This review article will focus on hydroa vacciniforme-like lymphoproliferative disorder, extranodal NK/T-cell lymphoma, adult T-cell leukemia/lymphoma, lymphomatoid granulomatosis, and Epstein-Barr virus-positive mucocutaneous ulcers. We will review the pathogenesis of these conditions and the challenges of making a timely diagnosis in early-stage disease and discuss the common clinicopathologic manifestations, mutational landscape, and approaches to treat these highly aggressive and frequently lethal types of lymphoma.

A case of aleukemic leukemia cutis after COVID-19 infection presenting as facial rash

Aleukemic leukemia cutis (ALC) is a rare condition that is characterized by leukemic cells in the skin before presenting in the peripheral blood or bone marrow. We report a case of a 43-year-old woman who underwent assessment for bilateral facial nodules arising 1 month after COVID-19 infection. A punch biopsy specimen showed a malignant neoplasm primarily composed of immature blasts dissecting through the collagen in the dermis, concerning for myeloid sarcoma versus leukemia cutis. Bone marrow and blood specimens were negative for hematologic malignancy. The patient was appropriately treated with chemotherapy and is recovering well. This report highlights an interesting case of ALC following COVID-19 infection presenting as an isolated facial rash. Whether there is a true relationship between the patient's COVID-19 infection and her abrupt presentation of leukemia remains unclear, but we wanted to present this case regardless in effort to highlight a potentially unique association requiring further study.

Abstract 3764: Expression patterns of microRNAs and associated target genes in ulcerated primary cutaneous melanoma

Tumor ulceration in cutaneous melanoma represents one of the top prognostic indicators for clinical outcome, associated with reduced progression free and overall survival. Despite this influence, the underlying biology driving tumor ulceration remains largely unexplored. One of the potential mediators of ulceration are microRNAs (miRNAs). These short, non-coding RNAs are frequently dysregulated in cancer and can impact tumor biology via mediation of gene expression. Distinct miRNA expression patterns have been identified in melanoma that can function as predictive biomarkers of disease progression and metastasis. However, the presence of a unique miRNA profile in ulcerated melanoma has not yet been assessed.

miRNA and mRNA expression was assessed in 35 ulcerated and non-ulcerated cutaneous melanomas using the NanoString Human miRNA and Tumor Signaling 360 mRNA assays and validated in an independent cohort. Linear models and moderated t-tests were used to detect differential expression between ulcerated and non-ulcerated tumors. Pathway enrichment and functional annotations were determined using public databases. Pearson correlations were employed to predict miRNA-mRNA binding pairs. Differentially expressed mRNAs were identified as miRNA targets using Ingenuity Pathway Analysis.

Comparison between groups revealed significant upregulation of 13 miRNAs in ulcerated relative to non-ulcerated tumors (p &lt;0.03). 4 of these miRNAs were also significantly upregulated in the validation cohort (miR-363-3p, miR-196b-5p, miR-135b-5p and miR-223-3p, p &lt;0.02). Conversely, 11 miRNAs were significantly downregulated in ulcerated relative to non-ulcerated tumors (p &lt;0.05), of which, miR-376c-5p was also significantly downregulated in the validation cohort (p=0.009). 21 mRNAs were differentially expressed in ulcerated relative to non-ulcerated tumors, with 3 being significant in the validation cohort as well (FPR, IL-11, and ADM, p &lt;0.05). 9 of these 21 mRNAs were then identified as predicted targets of multiple differentially expressed miRNAs in ulcerated tumors. 2 of the differentially expressed mRNAs had an inverse correlation in expression with regulatory miRNAs in our tumor samples (SOCS3 and miR-218-5p, and IL7R and miR-376c-5p). Each of the mRNAs significantly upregulated in both the original and validation cohorts have been previously associated with angiogenesis, migration or pro-metastatic cell survival in the context of cancer and pathway analysis identified significant enrichment for “granulocyte adhesion and diapedesis” (p=0.02) in ulcerated tumors.

This study demonstrates that a unique subset of miRNAs and mRNAs are differentially expressed in ulcerated melanoma when compared to non-ulcerated. These findings also provide novel insight regarding how increased angiogenesis and metastasis may contribute to melanoma tumor ulceration.

Citation Format: Emily Schwarz, Mallory J. DiVincenzo, Casey Ren, Zoe Barricklow, Maribelle Moufawad, Lianbo Yu, Paolo Fadda, Colin Angell, Sara Zelinskas, Steven Sun, John H. Howard, Catherine Chung, Craig Slingluff, Alejandro A. Gru, Kari Kendra, William E. Carson. Expression patterns of microRNAs and associated target genes in ulcerated primary cutaneous melanoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3764.

Histopathologic and molecular characterization of BAP-1-inactivated melanoma

BACKGROUND

BRCA1-associated protein 1 (BAP-1) is a deubiquitylase that functions as a tumor suppressor, regulating multiple cellular processes including cell cycle control, differentiation, cell death, and DNA repair. BAP-1-inactivated melanocytic tumors (BIMTs) have recently been described and are characterized by epithelioid cytomorphology, are often clonal in appearance, and typically do not recur or show malignant transformation on follow-up.

AIM

To describe the histopathologic and molecular characterization of five cases of BAP-1-inactivated cutaneous malignant melanomas.

METHODS

The archives at two separate institutions were retrospectively searched for tumors classified as melanoma with loss of BAP-1 via immunohistochemistry. Five cases were identified. These cases were classified as malignant melanoma based on cytomorphology, immunohistochemistry, and ancillary molecular testing. The clinical demographics were recorded, along with the histomorphologic features of each case. Genomic analysis for all cases was performed via OncoScan.

RESULTS

The five reviewed cases consisted of two females and three males ranging from 67 to 74 years in age. Molecular characterization of each case was performed using OncoScan. Microarray assay showed that there was a complete deletion of 3p in all cases, BRAF V600E mutation in two cases, NRAS missense variant in one case, and loss of 9p in three cases. All cases showed malignant copy number alterations.

CONCLUSIONS

Herein we describe five cases of BAP-1-inactivated melanomas confirmed by histomorphology and immunohistochemistry, all of which show malignant copy number profiles including loss of 3p. In addition, we provide a case of a likely BIMT showing progression to BAP-1-inactivated melanoma on a 16-year follow-up.

Expression Patterns of microRNAs and Associated Target Genes in Ulcerated Primary Cutaneous Melanoma

Ulcerated cutaneous melanoma carries a poor prognosis, and the underlying biology driving its aggressive behavior is largely unexplored. MicroRNAs (miRs) are small, noncoding RNAs that inhibit the expression of specific genes and exhibit dysregulated expression patterns in cancer. We hypothesized that a unique miR profile exists in ulcerated relative to nonulcerated melanoma and that miR expression inversely correlates with target genes of biologic importance. Expression of miRs and mRNAs was assessed in ulcerated and nonulcerated cutaneous melanomas using the NanoString Human miRNA and Tumor Signaling 360 mRNA assays and validated in an independent cohort. Pathway enrichment and functional annotations for differentially expressed miRs and mRNAs were determined using publicly available databases. Pearson correlations were employed to predict potential miR‒mRNA binding pairs. Ulcerated melanoma tissue showed at least 1.5-fold change in relative expression of 24 miRs, including miR-206, miR-1-3p, and miR-4286 (>2.25-fold decrease, P < 0.048) and miR-146a-5p, miR-196b-5p, and miR-363-3p (>2.5-fold increase, P < 0.014). Ulcerated melanomas also had 21 differentially expressed mRNAs relative to nonulcerated tumors (P < 0.01), among which two had an inverse correlation in expression with regulatory miRs (SOCS3 and miR-218-5p and IL7R and miR-376c-5p). This miR expression profile adds to the molecular characterization of the poorly understood histopathologic phenotype of ulcerated melanoma.

Acute Epstein-Barr virus infection resembling cutaneous T-cell lymphoma

Primary, acute Epstein-Barr virus (EBV) infection is associated with a variety of cutaneous eruptions, including the viral exanthem of infectious mononucleosis and erythema multiforme. Latent, chronic EBV infection can rarely result in development of lymphoproliferative disorders with cutaneous manifestations; however, these disorders do not arise from primary infection. In this report, we present a case of primary, acute EBV infection presenting with histopathologic features closely mimicking aggressive cytotoxic cutaneous T-cell lymphoma.

Microsecretory adenocarcinoma of the external ear canal

Microsecretory adenocarcinoma (MSA) is a recently described salivary gland tumor characterized by unique histomorphologic and immunohistochemical features as well as recurrent MEF2C::SS18 gene fusion. Since 2019, 24 cases have been reported in the literature, primarily arising in the oral cavity, with a single reported case arising in the parotid gland. Here, we present a case of MSA that arose in the external ear canal in an 89-year-old woman and was discovered during management of vertigo symptoms. Excisional biopsy of the lesion showed multiple fragments of squamous epithelium with hyperplastic changes and a distinct subepithelial infiltrating neoplasm composed of bland cells forming tubules and cords. Neoplastic cells expressed keratin, S100 protein, p63, and TLE1 and did not express p40, mammaglobin, pan-TRK, synaptophysin, or chromogranin by immunohistochemistry. SS18 gene rearrangement was shown with break-apart fluorescent in situ hybridization. Overall, the histomorphologic, immunohistochemical, and cytogenetic findings confirm a diagnosis of MSA arising in a unique extraoral location.

Tertiary lymphoid structures in desmoplastic melanoma have increased lymphocyte density, lymphocyte proliferation, and immune cross talk with tumor when compared to non-desmoplastic melanomas

Tertiary lymphoid structures (TLS) are ectopic lymphoid structures that can arise in human cancers and are associated with improved overall survival (OS) and response to immune checkpoint blockade (ICB) in several cancers, including non-desmoplastic metastatic melanoma (NDMM). Desmoplastic melanoma (DM) has one of the highest response rates to ICB, and we previously identified that primary DM (PDM) contains TLS. Despite the association of TLS with survival and ICB response, it is unknown whether TLS or associated markers of immune activity can differ between PDM and NDMM. We hypothesized that PDM would contain higher frequencies of TLS than NDMM, that T and B-cell densities and proliferation would be greater in TLS of PDM than TLS of NDMM, and that proliferation rates of T and B-cells in PDM TLS would be concordant with those of intratumoral lymphocytes. We found that four features of TLS in PDM distinguish them from TLS in NDMM. TLS were peritumoral in NDMM but intratumoral in PDM. CD8⁺ T-cell and CD20⁺ B-cell densities and proliferative fractions were higher in PDM TLS than NDMM TLS. Additionally, the proliferative fractions of T- and B-cells were concordant between the TLS and tumor site in PDM and discordant in NDMM. Collectively, these data suggest that TLS and associated immune markers can differ across melanoma subsets and suggest that PDM TLS may be more immunologically active and have enhanced immune cell trafficking between tumor and TLS compared to NDMM.

Poorly differentiated cutaneous apocrine carcinomas: histopathological clues and immunohistochemical analysis for the diagnosis of this unusual neoplasm

Primary cutaneous apocrine carcinoma (PCAC) is a rare cutaneous malignancy that is derived from apocrine glands. Histologically, these tumours can appear well-differentiated where diagnosis should be relatively straightforward. However, occasionally these tumours can exhibit high-grade features, and in such instances the diagnosis can be challenging. A retrospective analysis of 12 cases of poorly differentiated PCAC, obtained from large academic institutions, was performed, and summarised below. Immunohistochemical studies were performed in all cases with antibodies against CK7, p63, CAM 5.2, GCDFP-15, GATA3, CEA, PR, ER, HER2, calponin, SMA, androgen receptor and EMA. All 12 cases were poorly differentiated; however, there were some histopathological clues to the diagnosis of apocrine carcinoma; namely, the presence of focal glandular formation, acrosyringial involvement and the presence of single 'pagetoid' cells within epidermis. All tumours were consistently positive for CK7, GATA3 and GCDFP-15 and negative for p63. The tumours had variable expression of CAM5.2, CEA, ER, PR, HER2, androgen receptor and EMA. In three cases, there was a preservation of the myoepithelial cell layer (with calponin and SMA), which also confirmed the primary cutaneous origin. PCAC is a difficult neoplasm to diagnose, as it can appear identical to metastatic carcinomas. We describe 12 cases of poorly differentiated PCAC, highlighting their salient clinical, histopathological and immunohistochemical features, and discuss the potential diagnostic pitfalls in distinguishing this entity from other malignant neoplasms. Our results indicate that a combination of thorough histological inspection coupled with an adequate battery of immunohistochemical stains is necessary to support the diagnosis of PCAC.

Sclerodermiform Lupus Erythematosus: A Series of Five Patients

Background

Sclerodermiform lupus erythematosus (SDLE) is a rare Type 3 overlap syndrome of morphea and cutaneous lupus diagnosed with histopathologic features of both diseases present. It was first reported in 1976 by Umbert et al with a case series of four patients. SDLE is more common in young to middle-aged female patients.

Methods

After IRB approval, we searched our internal pathology database for cases of SDLE, excluded any patients that did not fulfill the diagnostic criteria, and verified each case with a board-certified dermatopathologist.

Results

Five patients with SDLE were identified; three of the patients are male and three are Black. Consistent with prior reports in the literature, the lesions were described as hyperpigmented plaques or nodules. The most commonly involved location was the extremities. Histopathology showed diffuse sclerosis in all five patients' biopsies, vacuolar interface changes in three biopsies, basement membrane thickening in one biopsy, and increased dermal mucin deposition in two of the four biopsy specimens stained with colloidal iron. Improvement was noted in patients treated with topical, intralesional, or systemic corticosteroids, topical calcineurin inhibitors, and oral antimalarials.

Conclusion

We describe five cases of SDLE which is the largest series to date and the first series with a majority of patients being male. Improved recognition and a more thorough understanding of SDLE is necessary for appropriate diagnosis and management.

Best Practices in CD30 Immunohistochemistry Testing, Interpretation, and Reporting: An Expert Panel Consensus

CONTEXT.—

Although CD30 testing is an established tool in the diagnostic workup of lymphomas, it is also emerging as a predictive biomarker that informs treatment. The current definition of CD30 positivity by immunohistochemistry is descriptive and based on reactivity in lymphomas that are defined by their universal strong expression of CD30, rather than any established threshold. Challenges include inconsistencies with preanalytic variables, tissue processing, pathologist readout, and with the pathologist and oncologist interpretation of reported results.

OBJECTIVE.—

To develop and propose general best practice recommendations for reporting CD30 expression by immunohistochemistry in lymphoma biopsies to harmonize practices across institutions and facilitate assessment of its significance in clinical decision-making.

DESIGN.—

Following literature review and group discussion, the panel of 14 academic hematopathologists and 2 clinical/academic hematologists/oncologists divided into 3 working groups. Each working group was tasked with assessing CD30 testing by immunohistochemistry, CD30 expression readout, or CD30 expression interpretation.

RESULTS.—

Panel recommendations were reviewed and discussed. An online survey was conducted to confirm the consensus recommendations.

CONCLUSIONS.—

CD30 immunohistochemistry is required for all patients in whom classic Hodgkin lymphoma and any lymphoma within the spectrum of peripheral T-cell lymphoma are differential diagnostic considerations. The panel reinforced and summarized that immunohistochemistry is the preferred methodology and any degree of CD30 expression should be reported. For diagnostic purposes, the interpretation of CD30 expression should follow published guidelines. To inform therapeutic decisions, report estimated percent positive expression in tumor cells (or total cells where applicable) and record descriptively if nontumor cells are positive.

Angiosarcoma-like Kaposi Sarcoma: A Distinctive Histomorphologic Variant Representing an Important Diagnostic Pitfall

Kaposi sarcoma (KS) is a rare low-grade angioproliferative neoplasm associated with human herpesvirus 8 (HHV-8) infection with multiple clinical subtypes and varying histopathologic patterns. Histologically, many different variants of KS have been reported, yet all can be difficult to recognize and must be differentiated from other vascular tumors. In this report, we studied fourteen cases of a newly described variant of KS reminiscent of a well-differentiated angiosarcoma (angiosarcoma-like KS). All cases showed a diffuse, ill-defined infiltrative dermal-based lesion composed of numerous anastomosing vascular channels of varying caliber lined by a single layer of endothelium with minimal pleomorphism. The vascular proliferation ramified through the dermis and dissected the collagen bundles along with infiltration into the subcutaneous fat and around skin appendages. All cases showed expression of vascular markers (CD31, CD34, and ERG) and were positive for HHV-8. None showed the classic histopathology associated with KS. Without clinical guidance these tumors can be difficult to recognize as KS, creating significant diagnostic challenges. Our study expands on a rare histologic variant of KS that ought to be considered in the differential diagnosis of any cutaneous well-differentiated angiosarcoma. Awareness of this variant of KS is of important for proper diagnosis and management of these patients; thus, careful attention to the histomorphology and clinical history can help lead the pathologist to the correct diagnosis.

Liver kinase B1 (LKB1) in murine erythroid progenitors modulates erythropoietin setpoint in association with maturation control

Erythropoiesis is a tightly regulated process. It is stimulated by decreased oxygen in circulation, which leads to the secretion of the hormone erythropoietin (Epo) by the kidneys. An additional layer of control involves the coordinated sensing and use of nutrients. Much cellular machinery contributes to sensing and responding to nutrient status in cells, and one key participant is the kinase LKB1. The current study examines the role of LKB1 in erythropoiesis using a murine in vivo and ex vivo conditional knockout system. In vivo analysis showed erythroid loss of LKB1 to be associated with a robust increase in serum Epo and mild reticulocytosis. Despite these abnormalities, no evidence of anemia or hemolysis was found. Further characterization using an ex vivo progenitor culture assay demonstrated accelerated erythroid maturation in the LKB1-deficient cells. Based on pharmacologic evidence, this phenotype appeared to result from impaired AMP-activated protein kinase (AMPK) signaling downstream of LKB1. These findings reveal a role for LKB1 in fine-tuning Epo-driven erythropoiesis in association with maturational control.

An Analysis of the Pathologic Features of Blastic Plasmacytoid Dendritic Cell Neoplasm Based on a Comprehensive Literature Database of Cases

CONTEXT.—

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with poor outcome. BPDCN diagnostically overlaps with entities such as acute myeloid leukemia, histiocytic/dendritic cell neoplasms, and natural killer/T-cell lymphomas. Unfortunately, large, patient-centered studies that comprehensively analyze clinical, pathologic, and other diagnostic features are lacking. As such, there is an incomplete understanding of this disease.

OBJECTIVE.—

To better characterize BPDCN, a multicenter working group consisting of hematopathologists and dermatopathologists gathered in person and remotely to review the current understanding of BPDCN, discuss specific issues regarding the diagnosis and differential diagnosis, and perform a retrospective analysis of the literature.

DATA SOURCES.—

The working group curated a database of published BPDCN patient cases (BPDCN Network literature database) following careful discussion and review, 361 articles were identified, comprising a total of 1513 individually annotated patients.

CONCLUSIONS.—

By conducting an in-depth analysis, not only did we confirm known findings such as frequent skin involvement (84% of patients; 861 of 1028) and a male predominance among older patients (>60 years old; male to female ratio of 3.5:1; 617:177), but we also identified a number of underrecognized features, such as significant central nervous system involvement (38% of cases; 24 of 64), and a more equal male to female prevalence among patients younger than 40 years (male to female ratio of 1.25:1; 167:134). Furthermore, we were able to accurately summarize the immunophenotypic, cytogenetic, and molecular features of this disease. BPDCN is a complex disease with distinct morphologic, immunophenotypic, and molecular findings. Continual updates of the literature database generated here and further analysis can allow for prospective refinement of our understanding of this orphan disease.

An Update on EBV and HTLV-1 Induced Cutaneous Manifestations. A Review of the Ibero-American Society of Dermatopathology (SILADEPA). CME Part II

The Epstein Barr virus (EBV) is a DNA virus that infects 90% of the human population, is responsible for certain cutaneous lymphomas (extranodal NK/T-cell lymhoma, hydroa vacciniforme lymphoproliferative disorder, lymphomatoid granulomatosis, others), and can be associated with a variety of cutaneous manifestations (e.g. infectious mononucleosis, severe mosquito bite allergy, chronic active EBV disease, Gianotti Crosti syndrome). EBV-related skin disorders are frequent in certain populations (South and Cental America, Africa, Asia, and Oceania) and can be diagnostically challenging. The human T-lymphotropic virus type-1 (HTLV-1) is a retrovirus which is known to be associated with adult T-cell leukemia/lymphoma, neurologic disorders, but also cutaneous non-neoplastic manifestations (infective dermatitis, infections, and infestations). We performed an updated revision of the clinical dermatologic and histopathologic findings associated with the cutaneous non-neoplastic and preneoplastic disorders occurring in association with the EBV and HTLV-1 virus.

Malignant chondroid syringoma: A systematic review

Malignant Chondroid Syringomas (MCS) are very rare malignant tumours arising from cutaneous sweat glands, with only 51 reported cases in the literature. These tumours can metastasize and cause death if not treated adequately. While there are histological criteria to diagnose MCS tumours, there are no established criterion to determine which tumours are more or less likely to metastasize. A systematic review was performed to establish if any features of the primary MCS tumour are associated with risk of metastasis or patient mortality, as well as the efficacy of common treatment options. The literature search was performed using the Ovid Medline and Web of Science databases from inception through March 2020. This yielded 47 case reports corresponding to 51 unique patients. Statistical analysis of the collected data revealed none of the commonly accepted malignant histopathologic findings (including nuclear atypia and/or pleomorphism, mitotic figures, an infiltrative growth pattern, presence of satellite nodules, necrosis, and vascular and/or perineural invasion) of the primary tumour to be significantly more associated with metastatic risk or death. However, gross characteristics of the tumour, including size (greater than 5 cm) and truncal location of the primary lesion, were found to be associated with a higher risk of metastasis. The most effective treatment modality was wide local excision. Overall, primary MCS tumours, especially those greater than 5 cm or located on the trunk, should be treated with a wide local excision and followed closely to confirm no lesion recurrence or distant metastasis.

Use of Ultrasensitive RNA In Situ Hybridization for Determining Clonality in Cutaneous B-Cell Lymphomas and Lymphoid Hyperplasia Decreases Subsequent Use of Molecular Testing and Is Cost-effective

Primary cutaneous B-cell lymphomas (PCBCLs) are diagnostically challenging entities due to significant overlap in clinical and morphologic features with reactive lymphoid proliferations. Traditional methods for evaluating clonality such as immunohistochemistry (IHC) and chromogenic in situ hybridization (CISH) are limited by low sensitivity, which leads to additional costly and time-consuming molecular clonality assays. More recent technology has introduced ultrasensitive bright-field RNA in situ hybridization (BRISH) to the field, which can detect single molecules of light-chain mRNA. The current study evaluated 274 cases of PCBCL in addition to atypical and reactive lymphoid infiltrates, with CISH or BRISH performed on 180 (65.7%). CISH was performed on 105 (58.3%), and BRISH was performed on 75 (41.7%). Significantly fewer immunoglobulin heavy-chain (IGH) rearrangement studies were performed on cases that were evaluated with BRISH as compared with CISH (P=0.02). Subgroup analysis demonstrated that cases with restriction by BRISH were significantly less likely to have subsequent IGH studies performed (P=0.01). The expected costs of cases using CISH versus BRISH were $1053.89 versus $810.32 to the patient and $245.63 versus $225.23 to the laboratory. The use of ultrasensitive BRISH to evaluate clonality in PCBCL reduced the use of IGH rearrangement studies when compared with CISH. In particular, cases with light-chain restriction by BRISH did not result in confirmatory molecular testing. Despite slightly higher costs to the laboratory to perform BRISH, routine use of this methodology can result in cost savings to both the patient and laboratory by decreasing the use of expensive molecular methods.

An accurate diagnosis of dermal CD8+ lymphoproliferative disorders requires clinicopathological and immunophenotypic correlation

Linked Article: Kempf et al. Br J Dermatol 2022; 186:887–897.

Primary cutaneous mucormycosis in a premature neonate treated conservatively with amphotericin B

Cutaneous mucormycosis is a rare, often fatal fungal infection that most commonly affects patients with underlying immunosuppression but also can occur in premature neonates. We report the case of an extremely premature boy (<25 weeks) who developed primary cutaneous mucormycosis shortly after birth. Although surgical debridement has been a mainstay of treatment in combination with antifungal therapy, our patient was successfully treated with amphotericin B alone-the management only reported in three other cases to date. We present this case to highlight that prompt initiation of treatment with amphotericin B alone may be an appropriate alternative to surgical intervention, particularly in patients with non-angioinvasive disease who are poor surgical candidates.

Primary Cutaneous CD4-Positive Small/Medium T-Cell Lymphoproliferative Disorder Mimicking Jessner Lymphocytic Infiltrate and Tumid Lupus-A Report of Two Cases

ABSTRACT

Primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder is a benign lymphoproliferative disorder composed of small-sized to medium-sized pleomorphic cells expressing a follicular helper T-cell phenotype. Jessner lymphocytic infiltrate and tumid lupus are cutaneous conditions characterized by the presence of rich dermal lymphocytic infiltrates with a superficial, deep, perivascular and periadnexal distribution that include copious amounts of dermal mucin deposition. We report 2 cases of primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder presenting with markedly increased dermal mucin, mimicking both Jessner lymphocytic infiltrate and tumid lupus and provide a review of the differential diagnosis and highlight key distinguishing features.

Primary Cutaneous Monomorphic Post-transplant Lymphoproliferative Disorder Mimicking Squamous Cell Carcinoma In Situ

ABSTRACT

Post-transplant lymphoproliferative disorder (PTLD) is a term used to describe a range of lymphoproliferative disorders that occur after solid organ transplant. Although the clinical presentation is variable, primary cutaneous PTLD typically presents as isolated nodules that appear as dermal-based proliferations. We present a case of a 70-year-old woman with a history of a kidney transplant who presented with a 2-month history of an asymptomatic, erythematous plaque on the right shin, clinically suspected to be squamous cell carcinoma in situ. Histomorphology demonstrated a dermal proliferation of atypical plasma cells with dense chromatin, variable nucleoli, and irregular nuclear borders. The atypical plasma cells were positive for Epstein-Barr virus by in situ hybridization and markedly kappa-restricted by RNAscope in situ hybridization. A diagnosis of cutaneous monomorphic PTLD, plasma cell neoplasm variant, was rendered, a rare diagnosis in the skin. Treatment for PTLD typically involves reduction of immunosuppression, although our patient progressed and developed new lesions despite this intervention. In this study, we present an atypical presentation of cutaneous PTLD, plasma cell neoplasm variant, presenting as squamous cell carcinoma in situ.

Reproducible Histopathologic Features in Cases of Basal Cell Carcinoma With Neuroendocrine Expression: A Clinicopathologic Study of 24 Cases With a Potential Diagnostic Pitfall

ABSTRACT

Basal cell carcinomas (BCCs) are common malignancies that usually show clear histomorphologic features, but in certain instances, it can display different patterns of differentiation leading to potential diagnostic confusion. BCCs with neuroendocrine differentiation/expression have been mentioned only briefly in the literature. In this study, we present cases of BCCs with neuroendocrine differentiation/expression that demonstrate reproducible histopathological features. Twenty-four cases were included in the study. All tumors showed conventional histopathologic features that are seen in BCCs, but in addition, all the tumors showed large, hyperchromatic, pleomorphic, mononuclear, and multinucleate cells with intracytoplasmic inclusions and intranuclear cytoplasmic invaginations, with rare cases showing stippled nuclei (salt-and-pepper appearance). These histologic features were somewhat concerning for a neuroendocrine carcinoma; thus, immunohistochemistry studies were performed in all cases at the time of diagnosis. By immunohistochemistry, all tumors showed expression of neuroendocrine markers. CD56 was expressed in all cases 24/24, chromogranin was positive in 17/24 cases, and synaptophysin 8/24 was positive in cases. This study confirms a subset of histopathologic features that are present in cases of BCC that are associated with neuroendocrine expression that can potentially be interpreted differently and can create a diagnostic pitfall. Neuroendocrine expression in BCCs is yet uncertain, and further studies are required to fully understand this phenomenon. To avoid diagnostic pitfalls, dermatopathologists must be aware of these unusual histopathologic features and aberrant immunostaining in such tumors; hence, it is advised to perform a thorough histologic inspection.

Granulomatous Facial Dermatoses

Noninfectious facial papular granulomas can be the presentation of several conditions, including granulomatous periorificial dermatitis, granulomatous rosacea, lupus miliaris disseminatus faciei, and papular sarcoidosis. Although these entities are treated distinctly from one another, they share several clinical and histological characteristics. We present 2 cases of facial papular granuloma: one patient presented with granulomatous rosacea, and the other had a presentation consistent with sarcoidosis but also demonstrated features of granulomatous periorificial dermatitis and had a protracted course of treatment. Such cases exemplify heterogeneity in the evaluation and management of this cutaneous lesion and highlight the necessity of appreciating its various potential causes.

Primary cutaneous follicle center lymphoma with aberrant CD8 expression

We report an unusual case of primary cutaneous follicle center lymphoma (PCFCL) with aberrant expression of the T-cell marker CD8. The patient is a 48-year-old male with no significant past medical history who presented with red indurated plaques on the abdomen. A punch biopsy showed abnormal lymphoid follicles in the dermis with reduced mantle zones and decreased tingible body macrophages. The epidermis was uninvolved. The follicles expressed CD20, PAX-5, and bcl-6 by immunohistochemistry. CD8, however, was strongly positive, highlighting neoplastic cells, which were negative for any additional T-cell markers. TIA and granzyme B were also negative. The patient underwent further staging workup, without evidence of nodal involvement. His course has been indolent thus far. In summary, we present a case of PCFCL with aberrant expression of the T-cell marker CD8, a finding not previously reported in the literature and a potential diagnostic pitfall.

Primary cutaneous anaplastic large-cell lymphoma with aberrant cytokeratin expression: An unusual mimicker of poorly differentiated carcinomas

An 81-year-old male presented with a rapidly growing cheek nodule. Biopsy revealed a dermal infiltrate of large atypical cells, some exhibiting a horseshoe-shaped nucleus. Immunohistochemistry revealed positivity for CD4, CD3, CD45, and CD30 (>95%). Melanocytic markers, cytotoxic markers, CD20, CD56, ALK1, synaptophysin, CD1a, and ETS-related gene (ERG) were negative. Notably, there was weak but diffuse expression of pan-cytokeratin (AE1/AE3) and Oscar keratin. There was also a weak expression of epithelial membrane antigen (EMA). CAM 5.2, p40, and IRF4/DUSP22 rearrangement were negative. Further staging revealed skin-limited disease. A diagnosis of primary cutaneous anaplastic large-cell lymphoma (PC-ALCL) was rendered. We present a rare case of cytokeratin positive PC-ALCL, a finding never reported in the literature. Both PC-ALCL and systemic ALCL (S-ALCL) evoke a broad differential. CD45, EMA, and cytokeratin stains help differentiate from metastatic carcinomas. There have been rare prior reports of cytokeratin expression in S-ALCL, which tend to stain with an unusual cytoplasmic and membranous pattern like our case, have variable co-expression of EMA, and null T-cell phenotypes. These show the significant diagnostic challenges that can arise in differentiating ALCL from metastatic or primary skin carcinomas. Awareness, careful attention to morphology (e.g., hallmark cells), and considering routine CD30 can help lead the pathologist to the correct diagnosis.

PLCγ1/PKCθ Downstream Signaling Controls Cutaneous T-Cell Lymphoma Development And Progression

Developing mechanistic rationales can improve the clinical management of cutaneous T-cell lymphomas (CTCL). There is considerable genetic and biological evidence of a malignant network of signaling mechanisms, highly influenced by deregulated TCR/PLCγ1 activity, controlling the biology of these lesions. In addition, activated STAT3 is associated with clinical progression, although the alterations responsible for this have not been fully elucidated. Here we studied PLCγ1-dependent mechanisms that can mediate STAT3 activation and control tumor growth and progression. Downstream of PLCγ1, the pharmacological inhibition and genetic knockdown of PKCθ inhibited STAT3 activation, impaired proliferation, and promoted apoptosis in CTCL cells. A PKCθ-dependent transcriptome in MF/SS cells revealed potential effector genes controlling cytokine signaling, TP53, and actin cytoskeleton dynamics. Consistently, an in vivo chicken embryo model xenografted with MF cells showed that PKCθ blockage abrogates tumor growth and spread to distant organs. Finally, the expression of a number of PKCθ target genes, found in MF cells, significantly correlated with that of PRKCQ (PKCθ) in 81 human MF samples. In summary, PKCθ can play a central role in the activation of malignant CTCL mechanisms via multiple routes, including, but not restricted to, STAT3. These mechanisms may, in turn, serve as targets for specific therapies.

Clonal cutaneous and neurosyphilis: A pitfall in pseudolymphoma diagnosis

Syphilis is a sexually transmitted infectious disease caused by the bacterium Treponema pallidum and can cause a wide variety of cutaneous manifestations, most commonly, a papulosquamous eruption of the trunk and extremities. Treatment with penicillin is curative. We report a case of a 69-year-old man who presented with recent onset of blurry vision and a nonpainful, nonpruritic eruption of pink-to-violaceous dermal nodules on his upper trunk and upper extremities. Biopsies of two separate locations revealed a dense superficial and deep perivascular atypical lymphocytic infiltrate with admixed plasma cells, histiocytes, and eosinophils. Some scattered cells expressed CD30, PD1, BCL-6, and ICOS. T-cell receptor (TCR)-rearrangement showed an identical TCR-gamma clone between both biopsy specimens. The patient was subsequently seen by ophthalmology and diagnosed with acute anterior uveitis. Rapid plasma reagin was reactive and cerebrospinal fluid studies showed findings consistent with a diagnosis of neurosyphilis. A T. pallidum immunostain of the skin biopsies was performed upon re-review, and was diffusely positive for spirochetes at the dermal-epidermal junction and within injured vessels. The patient was treated with penicillin G with near-resolution of his skin lesions. This case highlights the unusual ability of syphilis to mimic a T-cell lymphoma with matching clones across two different biopsy sites.

Solitary asymptomatic lobular perianal nodule on an infant

Folliculosebaceous cystic hamartoma (FSCH) is a benign lesion that presents as a solitary papule or nodule that typically affects the face and scalp of adults. A few reports have observed a congenital presentation. We present an infant boy exhibiting a tumor with overlap features between an FSCH and fibrofolliculoma in the perianal region that was first noticed at 6 months of age. The histological examination showed a hamartomatous benign proliferation of hair follicles and disordered sebaceous glands, which is consistent with the infundibular structures and radiating sebaceous glands that are typically observed in previously reported cases of FSCH. Sebaceous differentiation is a hallmark feature of FSCH. Folliculosebaceous cystic hamartoma is believed to be a late-stage form of trichofolliculoma (TF). Another consideration is that FSCH and TF are two distinct entities set apart by their degree of sebaceous or follicular differentiation and development of the mesenchymal stroma.

Next-generation sequencing confirms T-cell clonality in a subset of pediatric pityriasis lichenoides

BACKGROUND

Pityriasis lichenoides (PL) is a papulosquamous disease that affects both adults and children. Previous studies have shown a subset of this entity to have clonal T-cell populations via PCR-based assays. In this study, we sought to implement next-generation sequencing (NGS) as a more sensitive and specific test to examine for T-cell clonality within the pediatric population.

METHODS

We identified 18 biopsy specimens from 12 pediatric patients with clinical and histopathologic findings compatible with PL. Patient demographics, clinical features, management, and histopathologic findings were reviewed. All specimens were analyzed for clonality with NGS of T-cell receptor beta (TRB) and gamma (TRG) genes.

RESULTS

Of the 12 patients, 9 (75%) had complete resolution of lesions at the time of data collection (mean follow-up 31 months). The remaining three patients significantly improved with methotrexate (with or without acitretin). Interestingly, 7 of 12 patients (58%) and 9 of 17 biopsy specimens (53%) showed evidence of T-cell clonality. Two patients showed matching TRB clones from different anatomic sites.

CONCLUSIONS

T-cell clonality is a common finding in PL, probably representing a "reactive clonality" rather than a true lymphoproliferative disorder. Clonality alone cannot be used as a means to distinguish PL from lymphomatoid papulosis or cutaneous lymphoma.

Histomorphological and immunophenotypical spectrum of cutaneous myoepitheliomas: A series of 35 cases

Myoepithelial tumors comprise a group of mesenchymal lesions that show heterogeneous histomorphological features, including dual epithelial, neural, and myoid differentiation. Cutaneous myoepithelioma is a rare neoplasm that is composed primarily of myoepithelial cells and represents one end of a histopathological spectrum of cutaneous myoepithelial neoplasms including chondroid syringoma and myoepithelial carcinoma. These tumors display a wide histopathological spectrum and immunophenotypical profile often showing epithelial and myoepithelial differentiation. In this series, we studied 35 cases of cutaneous myoepitheliomas. Our cases highlighted the broad histopathological range where most cases showed a non-infiltrative and non-encapsulated tumor exclusively located in the dermis and with no subcutaneous involvement. The majority of our cases had a solid growth pattern (syncytial pattern) and the remainder of cases had a multinodular growth pattern. The tumor cells were epithelioid in 23 cases, spindled in eight cases and there was a mixture of epithelioid and spindled cells in four cases. Mitotic figures ranged from 0 to 5 per 10 HPF. By immunohistochemistry epithelial membrane antigen (EMA) was expressed in 59% of cases S100 was positive in 88% of cases, CAM 5.2 was positive in 16% of cases, AE1/AE3 was positive in 44% of cases, p63 was positive in 17% of cases, smooth muscle actin was positive in 38% of cases, desmin was positive in 6% of cases, calponin was positive in 22% of cases, and glial fibrillary acidic protein was positive in 36% of cases. In addition, there were five cases without EMA, keratin, or p63 expression that only showed S100 expression. We describe a large series of cutaneous myoepitheliomas delineating their histomorphological spectrum and immunophenotypical profile. Awareness of some of the unusual histopathological features and the heterogeneous immunohistochemical may pose difficulties for the diagnosis.

An unusual case of T-cell prolymphocytic leukemia mimicking a cutaneous vasculitis

T-cell prolymphocytic leukemia (T-PLL) is an aggressive post-thymic T-cell malignancy, which accounts for 2% of mature lymphocytic leukemias in adults. Though typically presenting with a brief history of B symptoms, hepatosplenomegaly, and marked lymphocytosis, erythematous or nodular skin rashes involving the trunk or limbs may be seen in 25% to 30% of patients, as well as a purpuric rash in a periorbital distribution. Cutaneous involvement typically presents in the context of patients with an established history of T-PLL, but it can less frequently present as an initial symptom heralding the diagnosis. An unusual case of T-PLL is described, presenting initially as palmoplantar ulcerated nodules with an initial biopsy suggestive of perniosis, followed by rapid progression of dark violaceous and bright red papules throughout the body after initiation of Obinutuzumab. The diagnosis of T-PLL was subsequently fully supported by the clinical, laboratory, cytologic, and immunophenotypic findings. This case highlights the importance of a multidisciplinary team approach to address such rare and atypical presentations.

Secondary skin involvement in classic Hodgkin lymphoma: Results of an international collaborative cutaneous lymphoma working group study of 25 patients

BACKGROUND

Cutaneous involvement by classic Hodgkin lymphoma (CHL) is an extraordinarily rare phenomenon in the current era. To date, no single large case series of cutaneous involvement by Hodgkin lymphoma has ever been reported in the literature.

METHODS

A comprehensive search for cases designated "skin" and "Hodgkin" was performed at different institutions between 1990 and 2020. Twenty-five cases were identified, and each case was independently reviewed by at least three board-certified dermatopathologists and/or hematopathologists.

RESULTS

All cases represented examples of systemic CHL with secondary skin dissemination. A single lesion, usually a tumor, nodule or infiltrative plaque was observed in 56% of cases and multiple lesions were present in 28% of cases. Most patients (86%-12/14) had a diagnosis of stage IV disease at first diagnosis. The interval between the clinical (first) diagnosis of HL and the development of skin lesions ranged between 6 and 108 months (average 33.75 months). Comprehensive histopathologic evaluation of these cases (at the initial diagnosis) revealed a diagnosis of classic HL not otherwise specified (NOS) in 60% of cases (15/25), nodular sclerosis type in 24% (6/25), mixed cellularity in 12% (3/25), and lymphocyte depleted in 4% (1/25).

CONCLUSIONS

We provide documentation of a large series of CHL with secondary skin involvement in association with CHL with additional clinical, morphologic, and immunophenotypic features.

PRAME immunohistochemistry as an adjunct for diagnosis and histological margin assessment in lentigo maligna

AIMS

Lentigo maligna (LM), the most common type of melanoma in situ, is a diagnostically challenging lesion for pathologists due to abundant background melanocytic hyperplasia in sun-damaged skin. Currently, no laboratory methods reliably distinguish benign from malignant melanocytes. However, preferentially expressed antigen in melanoma (PRAME) has shown promise in this regard, and could potentially be applied to diagnosis and margin assessment in difficult cases of LM.

METHODS AND RESULTS

Ninety-six cases with a diagnosis of LM (n = 77) or no residual LM (n = 19) following initial biopsy were identified and stained with an antibody directed towards PRAME. Immunohistochemistry (IHC) was scored as positive or negative, and measurement of histological margins by PRAME was performed and compared to the measurement of histological margins using conventional methods [haematoxylin and eosin (H&E) and/or sex-determining region Y-box 10 (SOX10) and/or Melan-A]. Of cases with LM, 93.5% (72 of 77) were PRAME+ and 94.7% (18 of 19) of cases with no residual LM were PRAME- . Of the 35 cases with no margin involvement by PRAME or conventional assessment, 14 cases (40.0%) had no difference in measurement, 17 (48.6%) had a difference of 1 mm or less and four (11.4%) differed by between 1 and 3.5 mm. There was a high correlation between margin assessment methods (r = 0.97, P < 0.0001).

CONCLUSIONS

PRAME IHC is a sensitive (93.5%) and specific (94.7%) method for diagnosing LM on biopsy and excision, and measurement of histological margins by PRAME shows a high correlation with conventional methods for margin assessment. Furthermore, the nuclear expression of PRAME makes it a good target for use in dual-colour IHC stains.

IDO1 Expression in Melanoma Metastases Is Low and Associated With Improved Overall Survival

Indoleamine 2-3 dioxygenase 1 (IDO1) expression may contribute to immunologic escape by melanoma metastases. However, a recent clinical trial failed to identify any clinical benefits of IDO1 inhibition in patients with unresectable metastatic melanoma, and prior characterizations of IDO1 expression have predominately studied primary lesions and local metastases, generating uncertainty regarding IDO1 expression in distant metastases. We hypothesized that IDO1 expression in such lesions would be low and correlated with decreased overall survival (OS). Metastases from patients (n=96) with stage IIIb to IV melanoma underwent tissue microarray construction and immunohistochemical staining for IDO1. Th1-related gene expression was determined quantitatively. Associations between OS and IDO1 expression were assessed with multivariate models. Of 96 metastatic lesions, 28% were IDOpos, and 85% exhibited IDO1 expression in <10% of tumor cells. IDOpos lesions were associated with improved OS (28.9 vs. 10.5 mo, P=0.02) and expression of Th1-related genes. OS was not associated with IDO1 expression in a multivariate analysis of all patients; however, IDO1 expression (hazard ratio=0.25, P=0.01) and intratumoral CD8+ T-cell density (hazard ratio=0.99, P<0.01) were correlated with OS in patients who underwent metastasectomy with curative-intent. IDOpos metastases were less likely to recur after metastasectomy (54% vs. 16%, P=0.01). IDO1 expression was low in melanoma metastases and correlated with OS after metastasectomy with curative-intent. Intratumoral CD8+ T cells and Th1-related genes were correlated with IDO1 expression, as was tumor recurrence. These suggest that IDO1 expression may be a marker of immunologic tumor control, and may inform participant selection in future trials of IDO1 inhibitors.