Immunohistochemistry in melanocytic lesions: Updates with a practical review for pathologists

Digital quantification of Ki67 and PRAME in challenging melanocytic lesions - A novel diagnostic tool

The interpretation of immunohistochemical markers in melanocytic lesions possesses difficulties due to expression in non-melanocytic cells and the time-consuming, non-reproducible nature of manual assessment. A digital tool that accurately quantifies Ki67 and PRAME may valuably aid pathologists in the diagnostic classification of melanocytic lesions. The aim of this study was to assess the diagnostic performance of digitally quantified Ki67 and PRAME in challenging melanocytic lesions utilizing double nuclear staining methods for accurate identification of melanocytic cells. We explored the difference in Ki67 and PRAME expression by WHO-lesion-groups and Melanocytic Pathology Assessment Tool and Hierarchy for Diagnosis version 2.0 (MPATH-Dx V2.0). Tissue slides from a cohort of 156 melanocytic lesions were stained with the Ki67/SOX10 double nuclear stain and the PRAME/SOX10 virtual double nuclear stain. Melanocytic cell specific Ki67/SOX10- and PRAME/SOX10-indexes were quantified by AI-driven digital image analysis (DIA) and compared to non-specific Ki67- and PRAME-indexes. The results showed that ROC AUC of the Ki67/SOX10-index was increased compared to the non-specific Ki67-index (p < 0.001), as opposed to the AUC of the PRAME/SOX10-index compared to non-specific PRAME-index (p = 0.090). The medians of digitally quantified Ki67- and PRAME-indexes differed significantly for the overall WHO-groups and MPATH-Dx V2.0 classes (p < 0.001). In conclusion, we found that double nuclear staining improved the diagnostic performance of Ki67, but not PRAME. The combination of digitally quantified Ki67- and PRAME-indexes may potentially serve as a tool for diagnostic classification of challenging melanocytic lesions. The proposed diagnostic tool presents the results visually, graphically, and quantitatively to optimally aid the pathologist.

Pigmented Lesions of the Oral Mucosa: Clinical Presentation, Histology, and Recommendations for Management

Pigmented lesions of the oral cavity can present significant diagnostic challenges because of their diverse etiologies and similar clinical presentations. Understanding these lesions is crucial for correct diagnosis and management because the biologic behavior ranges from benign physiologic variations to aggressive malignancies. The spectrum of oral lesions can include melanin-associated and exogenous pigmented lesions such as physiologic pigmentation and an amalgam tattoo, reactive processes such as smoker's melanosis and post-inflammatory pigmentation, benign neoplasms such as melanocytic nevi, and malignant conditions such as oral mucosal melanoma. Unlike cutaneous malignant melanomas, mucosal melanomas show distinct molecular profiles, with a lower prevalence of BRAFV600E mutations and a higher prevalence of c-KIT (CD117) mutations, which impacts therapeutic approaches. While most oral pigmented lesions are benign, they require a careful clinical evaluation, and when indicated, a biopsy for definitive diagnosis. This comprehensive review enables clinicians to navigate the complicated spectrum of oral pigmented lesions for optimal patient care.

Oral Melanoma in Older Adults: Epidemiology, Molecular Landscape, and Treatment Strategies

Oral melanoma is an aggressive neoplasm arising from melanocytes in the mucosal epithelium, accounting for 0.2%-0.8% of all melanomas. Unlike cutaneous melanoma, it is not associated with UV exposure, and its pathogenesis involves complex genetic and molecular alterations. This neoplasm predominantly affects older adults (≥ 60 years). Clinically, lesions often present as macular or nodular with an exophytic growth pattern, sometimes ulcerated, and exhibit varied pigmentation. Diagnosis is further complicated by non-pigmented (amelanotic) variants that can resemble other oral pigmentations. Wide surgical excision remains the mainstay treatment, often combined with chemotherapy; however, recurrence and distant metastasis remain high. While immunotherapy has shown promise in other melanoma subtypes, its efficacy in oral melanoma remains uncertain. Treatment in older adults is particularly challenging due to comorbidities and treatment-related morbidity. This review summarizes the epidemiology, clinical features, and current treatment strategies for oral melanoma in older adults. Key advances in the molecular mechanisms underlying this neoplasm are also outlined. As a strategic approach, integrating oral melanoma screening into routine geriatric dental care, supported by diagnostic algorithms, may improve early detection, prognosis, and survival outcomes in this vulnerable population.

The Great Impostor: A challenging case of small-cell melanoma with isolated adrenal metastasis

Small-cell melanoma masquerading as an adrenal non-Hodgkin lymphoma. The index report illustrates the deceptive cytomorphologic features of a small cell type malignant melanoma metastatic to the adrenal gland. The diagnosis was confirmed by performing immunocytochemistry on the cell block sections. The key cytomorphologic mimics and their distinctive features have also been highlighted.

[Immunohistochemical examinations in malignant melanoma : Fundamentals and special aspects]

Immunohistochemical examinations have been used for many years in dermatopathology and pathology and have become an integral part of tumor diagnostics. The aim is to identify and classify tumor cells that express distinct antigens. Malignant melanoma can be characterized by a large number of well-described and standardized antibodies, so that immunohistochemical staining is used in the diagnosis of melanoma, the differential diagnosis of other tumors, the determination of tumor thickness, the diagnosis of tumor metastases, and also in the diagnosis of sentinel lymph nodes. Comprehensive knowledge of the expression profiles and specific staining patterns of the antibodies used is of great diagnostic relevance, with the aim of preventing misdiagnosis. The perfect antibody with high sensitivity and maximum specificity does not exist. Hence, immunohistochemistry does not replace the conventional assessment and interpretation of tumor samples. Only in symbiosis with clinical and conventional histological findings do immunohistochemical stains have a diagnostic value.

Appropriate Statistical Methods to Assess Cross-study Diagnostic 23-Gene Expression Profile Test Performance for Cutaneous Melanocytic Neoplasms

ABSTRACT

Comparing studies of molecular ancillary diagnostic tests for difficult-to-diagnose cutaneous melanocytic neoplasms presents a methodological challenge, given the disparate ways accuracy metrics are calculated. A recent report by Boothby-Shoemaker et al investigating the real-world accuracy of the 23-gene expression profile (23-GEP) test highlights this methodological difficulty, reporting lower accuracy than previously observed. However, their calculation method-with indeterminate test results defined as either false positive or false negative-was different than those used in previous studies. We corrected for these differences and recalculated their reported accuracy metrics in the same manner as the previous studies to enable appropriate comparison with previously published reports. This corrected analysis showed a sensitivity of 92.1% (95% confidence interval [CI], 82.1%-100%) and specificity of 94.4% (91.6%-96.9%). We then compared these results directly to previous studies with >25 benign and >25 malignant cases with outcomes and/or concordant histopathological diagnosis by ≥3 dermatopathologists. All studies assessed had enrollment imbalances of benign versus malignant patients (0.8-7.0 ratio), so balanced cohorts were resampled according to the lowest common denominator to calculate point estimates and CIs for accuracy metrics. Overall, we found no statistically significant differences in the ranges of 23-GEP sensitivity, 90.4%-96.3% (95% CI, 80.8%-100%), specificity, 87.3%-96.2% (78.2%-100%), positive predictive value, 88.5%-96.1% (81.5%-100%), or negative predictive value, 91.1%-96.3% (83.6%-100%) between previous studies and the cohort from Boothby-Shoemaker et al with this unified methodological approach. Rigorous standardization of calculation methods is necessary when the goal is direct cross-study comparability.

SEOM-GEM clinical guidelines for cutaneous melanoma (2023)

Cutaneous melanoma incidence is rising. Early diagnosis and treatment administration are key for increasing the chances of survival. For patients with locoregional advanced melanoma that can be treated with complete resection, adjuvant-and more recently neoadjuvant-with targeted therapy-BRAF and MEK inhibitors-and immunotherapy-anti-PD-1-based therapies-offer opportunities to reduce the risk of relapse and distant metastases. For patients with advanced disease not amenable to radical treatment, these treatments offer an unprecedented increase in overall survival. A group of medical oncologists from the Spanish Society of Medical Oncology (SEOM) and Spanish Multidisciplinary Melanoma Group (GEM) has designed these guidelines, based on a thorough review of the best evidence available. The following guidelines try to cover all the aspects from the diagnosis-clinical, pathological, and molecular-staging, risk stratification, adjuvant therapy, advanced disease therapy, and survivor follow-up, including special situations, such as brain metastases, refractory disease, and treatment sequencing. We aim help clinicians in the decision-making process.

Digital quantification of PRAME for distinguishing melanoma from nevi compared to manual assessment

AIMS

In this proof-of-concept study, we propose a new method for automated digital quantification of PRAME (PReferentially expressed Antigen of MElanoma) as a diagnostic aid to distinguish between benign and malignant melanocytic lesions. The proposed method utilizes immunohistochemical virtual double nuclear staining for PRAME and SOX10 to precisely identify the melanocytic cells of interest, which is combined with digital image analyse to quantify a PRAME-index.

METHODS

Our study included 10 compound nevi, 3 halo nevi, and 10 melanomas. Tissue slides were stained with PRAME, scanned, the cover glass removed, stained with SOX10, scanned again, and finally analysed digitally. The digitally quantified PRAME-index was compared with a manual qualitative assessment by a dermatopathologist using the standard PRAME-scoring system.

RESULTS

The digitally quantified PRAME-index showed a sensitivity of 70 % and a specificity of 100 % for separating melanomas from benign lesions. The manual qualitative PRAME-score showed a sensitivity of 60 % and a specificity of 100 %. Comparing the two methods using ROC-analyses, our digital quantitative method (AUC: 0.931, 95 % CI: 0.834;1.00, SD: 0.050) remains on par with the manual qualitative method (AUC: 0.877, 95 % CI: 0.725;1.00, SD: 0.078).

CONCLUSION

We found our novel digital quantitative method was at least as precise at classifying lesions as benign or malignant as the current manual qualitative assessment. Our method has the advantages of being operator-independent, objective, and replicable. Furthermore, our method can easily be implemented in an already digitalized pathology department. Given the small cohort size, more studies are to be done to validate our findings.

Deep learning model shows pathologist-level detection of sentinel node metastasis of melanoma and intra-nodal nevi on whole slide images

Introduction

Nodal metastasis (NM) in sentinel node biopsies (SNB) is crucial for melanoma staging. However, an intra-nodal nevus (INN) may often be misclassified as NM, leading to potential misdiagnosis and incorrect staging. There is high discordance among pathologists in assessing SNB positivity, which may lead to false staging. Digital whole slide imaging offers the potential for implementing artificial intelligence (AI) in digital pathology. In this study, we assessed the capability of AI to detect NM and INN in SNBs.

Methods

A total of 485 hematoxylin and eosin whole slide images (WSIs), including NM and INN from 196 SNBs, were collected and divided into training (279 WSIs), validation (89 WSIs), and test sets (117 WSIs). A deep learning model was trained with 5,956 manual pixel-wise annotations. The AI and three blinded dermatopathologists assessed the test set, with immunohistochemistry serving as the reference standard.

Results

The AI model showed excellent performance with an area under the curve receiver operating characteristic (AUC) of 0.965 for detecting NM. In comparison, the AUC for NM detection among dermatopathologists ranged between 0.94 and 0.98. For the detection of INN, the AUC was lower for both AI (0.781) and dermatopathologists (range of 0.63-0.79).

Discussion

In conclusion, the deep learning AI model showed excellent accuracy in detecting NM, achieving dermatopathologist-level performance in detecting both NM and INN. Importantly, the AI model showed the potential to differentiate between these two entities. However, further validation is warranted.

Pigmented Epithelioid Melanocytoma of the Penis: A Case Report

Pigmented epithelioid melanocytoma is rare cutaneous melanocytic proliferation, characterized by heavily pigmented melanocytes, with a potential for regional node metastasis, but with an overall favorable clinical course. Here, we describe an uncommon case of pigmented epithelioid melanocytoma involving the penis in an adolescent patient.

'Eczematous' dermatitis of the nipple: clinical and histopathological differential diagnosis of Paget disease

The nipple can be affected by many malignant and benign entities. A wide variety of diseases including Paget disease, atopic dermatitis and nipple candidiasis can cause eczema-like changes in the nipple. In cases of diagnostic uncertainty, tissue sampling may be indicated. A true eczematous lesion, such as atopic dermatitis, typically shows a spongiotic dermatitis pattern. Paget disease, on the other hand, presents with infiltration of the nipple epidermis by neoplastic cells. The presence of atypical cells scattered in the epidermis in a pagetoid pattern opens up a histopathological differential diagnosis encompassing squamous cell carcinoma in situ and malignant melanoma, among others. Immunohistochemistry is commonly used to render a diagnosis. The objective of this article is to discuss Paget disease and highlight relevant clinical and histopathological differential diagnoses.

Immunohistochemical double nuclear staining for cell-specific automated quantification of the proliferation index - A promising diagnostic aid for melanocytic lesions

AIMS

Pathologists often use immunohistochemical staining of the proliferation marker Ki67 in their diagnostic assessment of melanocytic lesions. However, the interpretation of Ki67 can be challenging. We propose a new workflow to improve the diagnostic utility of the Ki67-index. In this workflow, Ki67 is combined with the melanocytic tumour-cell marker SOX10 in a Ki67/SOX10 double nuclear stain. The Ki67-index is then quantified automatically using digital image analysis (DIA). The aim of this study was to optimise and test three different multiplexing methods for Ki67/SOX10 double nuclear staining.

METHODS

Multiplex immunofluorescence (mIF), multiplex immunohistochemistry (mIHC), and multiplexed immunohistochemical consecutive staining on single slide (MICSSS) were optimised for Ki67/SOX10 double nuclear staining. DIA applications were designed for automated quantification of the Ki67-index. The methods were tested on a pilot case-control cohort of benign and malignant melanocytic lesions (n = 23).

RESULTS

Using the Ki67/SOX10 double nuclear stain, malignant melanocytic lesions could be completely distinguished from benign lesions by the Ki67-index. The Ki67-index cut-offs were 1.8% (mIF) and 1.5% (mIHC and MICSSS). The AUC of the automatically quantified Ki67-index based on double nuclear staining was 1.0 (95% CI: 1.0;1.0), whereas the AUC of conventional Ki67 single-stains was 0.87 (95% CI: 0.71;1.00).

CONCLUSIONS

The novel Ki67/SOX10 double nuclear stain highly improved the diagnostic precision of Ki67 interpretation. Both mIHC and mIF were useful methods for Ki67/SOX10 double nuclear staining, whereas the MICSSS method had challenges in the current setting. The Ki67/SOX10 double nuclear stain shows potential as a valuable diagnostic aid for melanocytic lesions.

Diagnosing Cutaneous Melanocytic Tumors in the Molecular Era: Updates and Review of Literature

Over the past decade, molecular and genomic discoveries have experienced unprecedented growth, fundamentally reshaping our comprehension of melanocytic tumors. This review comprises three main sections. The first part gives an overview of the current genomic landscape of cutaneous melanocytic tumors. The second part provides an update on the associated molecular tests and immunohistochemical stains that are helpful for diagnostic purposes. The third section briefly outlines the diverse molecular pathways now utilized for the classification of cutaneous melanomas. The primary goal of this review is to provide a succinct overview of the molecular pathways involved in melanocytic tumors and demonstrate their practical integration into the realm of diagnostic aids. As the molecular and genomic knowledge base continues to expand, this review hopes to serve as a valuable resource for healthcare professionals, offering insight into the evolving molecular landscape of cutaneous melanocytic tumors and its implications for patient care.

An Update and Review of Clinical Outcomes Using Immunohistochemical Stains in Mohs Micrographic Surgery for Melanoma

BACKGROUND

Mohs micrographic surgery (MMS) provides optimal margin control through complete peripheral and deep margin assessment. The treatment of melanoma using MMS has historically been limited by difficulty in interpreting melanocytes using frozen sections. Immunohistochemical (IHC) staining, a technique whereby chromogen-tagged antibodies are used to detect antigens of interest, has revolutionized the surgical treatment of melanoma.

OBJECTIVES

This article provides an update and literature review of current IHC stains used in MMS for melanoma, their sensitivities and specificities, and clinical outcomes.

MATERIALS AND METHODS

A PubMed search was performed using keywords including "immunohistochemistry," "staining," and "Mohs surgery." Articles related to the use of IHC staining for the treatment of melanoma with MMS were included.

RESULTS

Six IHC stains met the criteria for the review including melanoma antigen recognized by T cells (MART-1), SRY-related HMG-box (SOX10), microphthalmia-associated transcription factor, HMB-45, MEL-5, S-100, and preferentially expressed antigen in melanoma.

CONCLUSION

The adaptation of IHC methods to frozen sections has enabled MMS to become a preferred treatment option for melanoma in special-site areas. Future studies are needed to standardize IHC techniques and to define best practices when using frozen section in the treatment of melanoma.

Diagnostic utility of the 23-gene expression profile test for an atypical intradermal melanocytic proliferation

Ancillary tests such as immunohistochemistry (IHC) and gene expression profile (GEP) testing may be needed to arrive at a definitive diagnosis for some atypical melanocytic neoplasms. A 34-year-old male with a family history of melanoma presented with a large, heterogeneous melanocytic lesion on the cheek. Histopathological review of two biopsies revealed an atypical intradermal melanocytic proliferation with spitzoid features without ulceration or regression. Scattered mitotic figures were identified. In addition to performing SOX10 IHC, PRAME and HMB45 staining highlighted weak, patchy positivity that was stronger in superficial, pleomorphic melanocytes (Ki-67, 5-7% mitotic rate). Based on these concerning but ambiguous IHC results and lingering concern for melanoma reiterated by other consulting dermatopathologists, the 23-GEP was requested for both specimens, which both returned a malignant result. The inconclusive histopathological features of malignancy were resolved by 23-GEP testing, facilitating a final diagnosis of malignant melanoma (pT3a, 2.5 mm Breslow depth, Clark's level IV).

Cutaneous Melanoma: A Review of Multifactorial Pathogenesis, Immunohistochemistry, and Emerging Biomarkers for Early Detection and Management

Cutaneous melanoma (CM) is an increasingly significant public health concern. Due to alarming mortality rates and escalating incidence, it is crucial to understand its etiology and identify emerging biomarkers for improved diagnosis and treatment strategies. This review aims to provide a comprehensive overview of the multifactorial etiology of CM, underscore the importance of early detection, discuss the molecular mechanisms behind melanoma development and progression, and shed light on the role of the potential biomarkers in diagnosis and treatment. The pathogenesis of CM involves a complex interplay of genetic predispositions and environmental exposures, ultraviolet radiation exposure being the predominant environmental risk factor. The emergence of new biomarkers, such as novel immunohistochemical markers, gene mutation analysis, microRNA, and exosome protein expressions, holds promise for improved early detection, and prognostic and personalized therapeutic strategies.

SOX10

The SOX gene encodes for transcription factors that are involved in embryogenesis and cell differentiation. Specifically, SOX10 aids with neural crest shuttling and development. In diagnostic histopathology, Sox10 immunostain is a helpful ancillary test due to its high sensitivity for melanocytic and peripheral nerve sheath neoplasms, and its role in distinguishing triple-negative breast carcinomas from gynaecological carcinoma, cutaneous adnexal neoplasms and salivary glands neoplasms from histological mimics.

Vitamin D Modulates the Response of Patient-Derived Metastatic Melanoma Cells to Anticancer Drugs

Melanoma is considered a lethal and treatment-resistant skin cancer with a high risk of recurrence, making it a major clinical challenge. Our earlier studies documented that 1,25(OH)₂D₃ and its low-calcaemic analogues potentiate the effectiveness of dacarbazine and cediranib, a pan-VEGFR inhibitor. In the current study, a set of patient-derived melanoma cultures was established and characterised as a preclinical model of human melanoma. Thus, patient-derived cells were preconditioned with 1,25(OH)₂D₃ and treated with cediranib or vemurafenib, a BRAF inhibitor, depending on the BRAF mutation status of the patients enrolled in the study. 1,25(OH)₂D₃ preconditioning exacerbated the inhibition of patient-derived melanoma cell growth and motility in comparison to monotherapy with cediranib. A significant decrease in mitochondrial respiration parameters, such as non-mitochondrial oxygen consumption, basal respiration and ATP-linked respiration, was observed. It seems that 1,25(OH)₂D₃ preconditioning enhanced cediranib efficacy via the modulation of mitochondrial bioenergetics. Additionally, 1,25(OH)₂D₃ also decreased the viability and mobility of the BRAF+ patient-derived cells treated with vemurafenib. Interestingly, regardless of the strict selection, cancer-derived fibroblasts (CAFs) became the major fraction of cultured cells over time, suggesting that melanoma growth is dependent on CAFs. In conclusion, the results of our study strongly emphasise that the active form of vitamin D, 1,25(OH)₂D₃, might be considered as an adjuvant agent in the treatment of malignant melanoma.

Expression of SATB2 in primary cutaneous sarcomatoid neoplasms: a potential diagnostic pitfall

SATB2 can be used as an immunohistochemical marker for osteoblastic differentiation. The differential diagnosis of a cutaneous sarcomatoid neoplasm sometimes includes osteosarcoma when the tumour concomitantly involves the skin, soft tissue, and bone, or when there is a past medical history of osteosarcoma. As the utility of SATB2 immunohistochemistry in these scenarios was unclear, we aimed to determine the frequency and the pattern of SATB2 expression in a variety of cutaneous sarcomatoid neoplasms. SATB2 expression by immunohistochemistry was evaluated by intensity (0-3) and extent (0-100%) of staining to generate an h-score for each case. Expression levels were classified into high-positive (h-score ≥100), low-positive (20-99), and negative (<20) groups. Positive SATB2 expression was observed in 18/23 (78%) atypical fibroxanthomas (AFX), 10/19 (53%) pleomorphic dermal sarcomas, 9/20 (45%) cutaneous sarcomatoid squamous cell carcinomas, 14/39 (36%) sarcomatoid melanomas, 2/13 (15%) poorly differentiated cutaneous angiosarcomas, 10/17 (59%) high-grade cutaneous leiomyosarcomas, and 7/8 (88%) osteosarcoma controls. With the exception of AFX, all cutaneous neoplasms showed significantly lower average h-scores than osteosarcoma. AFX gave the highest average h-score (71) and percentage of high-positive cases (48%) among all examined cutaneous neoplasms. Only two (1.5%) of all cutaneous cases showed strong intensity of staining. Common SATB2 expression in various cutaneous sarcomatoid neoplasms poses a potential diagnostic pitfall when the differential diagnosis includes osteosarcoma. Requirement of strong staining and a high-positive h-score improves the specificity of SATB2 in differentiating these tumours from osteosarcoma.

Canine melanoma: A review of diagnostics and comparative mechanisms of disease and immunotolerance in the era of the immunotherapies

Melanomas in humans and dogs are highly malignant and resistant to therapy. Since the first development of immunotherapies, interest in how the immune system interacts within the tumor microenvironment and plays a role in tumor development, progression, or remission has increased. Of major importance are tumor-infiltrating lymphocytes (TILs) where distribution and cell frequencies correlate with survival and therapeutic outcomes. Additionally, efforts have been made to identify subsets of TILs populations that can contribute to a tumor-promoting or tumor-inhibiting environment, such as the case with T regulatory cells versus CD8 T cells. Furthermore, cancerous cells have the capacity to express certain inhibitory checkpoint molecules, including CTLA-4, PD-L1, PD-L2, that can suppress the immune system, a property associated with poor prognosis, a high rate of recurrence, and metastasis. Comparative oncology brings insights to comprehend the mechanisms of tumorigenesis and immunotolerance in humans and dogs, contributing to the development of new therapeutic agents that can modulate the immune response against the tumor. Therapies that target signaling pathways such as mTOR and MEK/ERK that are upregulated in cancer, or immunotherapies with different approaches such as CAR-T cells engineered for specific tumor-associated antigens, DNA vaccines using human tyrosinase or CGSP-4 antigen, anti-PD-1 or -PD-L1 monoclonal antibodies that intercept their binding inhibiting the suppression of the T cells, and lymphokine-activated killer cells are already in development for treating canine tumors. This review provides concise and recent information about diagnosis, comparative mechanisms of tumor development and progression, and the current status of immunotherapies directed toward canine melanoma.

Hepatic steatosis with mass effect: A case report

BACKGROUND

Hepatic steatosis is a common radiologic finding. Some imaging inklings are the absence of a mass effect, and there is currently no report of hepatic steatosis with mass effect.

CASE SUMMARY

A 23-year-old female was admitted due to a liver mass for half a month. No obvious abnormalities were found in physical and laboratory examinations. Ultrasound, computed tomography, and magnetic resonance imaging showed a huge mass between the liver and stomach with a significant mass effect, and the caudate lobe and left lobe of the liver were involved. The signal on T2- and T1- weighted fat-saturated images of the mass was significantly reduced, and the enhanced scan showed inhomogeneous enhancement. Surgical and pathological findings indicated the diagnosis of hepatic steatosis. The operation and re-review of the patient's images showed that the lesion was supplied by the branch of the hepatic artery. The signal on T1-weighted out-of-phase images of the lesion was lower than on in-phase images, and there was no black rim cancellation artifact around the hepatic steatosis area on T1-weighted out-of-phase images. The dynamic enhancement pattern of the lesion was similar to that of the adjacent normal liver parenchyma. The above characteristics suggested that the lesion was hepatic steatosis. However, in this case, the lesion showed exogenous growth and was mass-like, with an obvious mass effect, which has not been reported previously.

CONCLUSION

Hepatic steatosis could grow exogenously and has an obvious mass effect. It needs to be distinguished from fat-rich tumors. The T1-weighted in- and out-of-phase images and dynamic enhanced scanning are valuable for differential diagnosis of this lesion.