Histopathological patterns of melanoma metastases in sentinel lymph nodes

Differentiation of benign nevoid rests and metastatic melanoma in sentinel lymph node biopsy

Patients with cutaneous melanoma routinely undergo sentinel lymph node (SLN) biopsy. If this first lymph node is clear, the entire lymph node basin is very likely to be free from the metastatic disease. Lymph node analysis is therefore of great importance with respect to prognostication and further management. Various cell types, including benign nevoid rests, can mimic metastatic melanomatous cells in the SLN. There is no standardized method to differentiate naevoid rests from metastatic melanoma. Diagnosis is based on cell location, morphology and multiple immunohistochemical techniques, with no single test being completely diagnostic. We present a patient with Lentigo Maligna melanoma, who was found to have benign nevoid rests on SLN biopsy, and discuss the diagnostic tests and considerations in differentiating benign nevoid rests from metastatic melanoma.

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

This review provides a summary of the immunohistochemical markers pertinent to the diagnosis of melanocytic lesions. There is considerable morphologic overlap between benign and malignant melanocytic lesions, and given the significant differences in clinical management, the diagnostic workup becomes crucial. Immunohistochemistry aids in the distinction between various melanocytic proliferations and recent contributions to the literature have furthered our optimization of panels in the diagnostic workup. In recent years, SOX10 has been considered as the optimal marker for melanocytic lesions given the similar sensitivity but higher specificity than S100. HMB-45 is less sensitive than S100 but demonstrates utility in confirmation of deceptively banal small cell and nevoid melanoma variants where deep nests of melanocytes are highlighted. Melan-A (MART-1) and MiTF show similar sensitivity to S100 however there is a lack of expression in spindle cell and desmoplastic melanomas.

Histopathologic and Molecular Diagnosis of Melanoma

Conventional histopathology is the primary means of melanoma diagnosis. Both architectural and cytologic features aid in discrimination of melanocytic nevi from melanoma. Communication between the clinician and pathologist regarding the history, examination, differential diagnosis, prior biopsy findings, method of sampling, and specimen orientation is critical to an accurate diagnosis. A melanoma pathology report includes multiple prognostic indicators to guide surgical and medical management. In challenging cases, immunohistochemistry and molecular diagnostics may be of benefit.

Three Types of Nodal Melanocytic Nevi in Sentinel Lymph Nodes of Patients With Melanoma: Pitfalls, Immunohistochemistry, and a Review of the Literature

The presence or absence of metastasis in sentinel lymph nodes often drives melanoma staging, prognosis, and treatment. However, distinguishing between metastatic melanoma cells and clusters of benign melanocytic nevus cells is not always straightforward. When morphologic hematoxylin and eosin interpretation alone is not sufficient, additional hematoxylin and eosin sections and immunohistochemical (IHC) studies may be beneficial. This review and small cases series of 3 diagnostically challenging melanocytic sentinel lymph node cases highlights the IHC approach to evaluate intraparenchymal nodal melanocytic nevi, coexistent metastatic melanoma with adjacent melanocytic nevi cells, and nodal blue nevi. In challenging cases, cytological morphology of the melanocytes, location within the lymph node, and IHC studies may assist in diagnosis. If these tools yield conflicting results, expert opinion is recommended.

A Non-cutaneous Form of Melanoma in a Goat during Meat Inspection: a Case Report

Malignant melanoma is a neoplasm that originates from melanocytes. This tumor is observed in cutaneous and non-cutaneous forms, and it is considered one of the most life-threatening types of cancers. Non-cutaneous melanoma is a complex of unique and malignant complications that are easily separable from cutaneous type. Since the ultraviolet radiation from the sun damages DNA and is an oxidative stress factor in melanoma and there are more melanocytes in the basal layer of skin than other parts of the body, the cutaneous form has more prevalence. Most of the time, non-cutaneous form is the result of cutaneous metastasis but both forms can occur primarily. Furthermore, non-cutaneous form usually happens in mucosal layers, intestines, and eyes; moreover, the main reasons are ectopic melanocytes or their unwanted regressive growing. Malignant melanoma can occur in all domestic animals; however, they seem to be rare in sheep and goats. Herein, we describe a rare case of the primary non-cutaneous form of malignant melanoma in a three-year-old indigenous female goat. During meat inspection procedures in a slaughterhouse in Tabriz, Iran, we encountered numerous round firm black masses on visceral surfaces and serous membranes of the abdominal and thoracic cavities. The liver and lungs were prominently affected. Samples were taken from involved parts, and malignant melanoma was confirmed in the histopathological examination due to pleomorphism and polymorphism and melanin pigments in cells with eosinophilic cytoplasm. According to what was stated in the "manual on meat inspection for developing countries", the carcass was not convenient for human use and condemned by the inspector.

Metastatic Melanoma With Features of Desmoplastic Melanoma in a Patient With Primary Cutaneous Superficial Spreading Melanoma With Epithelioid Features

ABSTRACT

The synchronous incidence of 2 different subtypes of melanoma is very rare. Desmoplastic melanoma (DM) can be a diagnostic challenge because of its frequent appearance as a dermal banal spindle cell proliferation. We present a case of a 30-year-old man who developed an irregular, purple, tender plaque measuring 2.5 cm on the right pretibial region. Wide excision of the right leg lesion showed superficial spreading melanoma with epithelioid cells and no spindle cell component. Sentinel lymph node (SLN) biopsy showed an atypical melanocytic proliferation involving one inguinal lymph node with subcapsular and intraparenchymal components. There were spindled tumor cells in lymph node capsule with hyperchromatic nuclei, which were nested within desmoplastic stroma, and were S100- and SOX10-positive and MART1- and HMB-45 negative; in addition to epithelioid tumor cells, which were S100-, SOX10-, and MART1-positive. Multiple discontinuous foci, subcapsular atypical melanocytes, and extracapsular extension helped in excluding capsular nevus. These findings were consistent with DM. Herein, we present an unusual case of primary cutaneous superficial spreading melanoma of the right leg with a predominantly epithelioid morphology that developed metastases to the SLN. The metastasis exhibited divergent differentiation, including both epithelioid morphology identical to the primary, but with additional features of DM that were nonoverlapping with the primary lesion.

Improved survival prognostication of node-positive malignant melanoma patients utilizing shotgun proteomics guided by histopathological characterization and genomic data

Metastatic melanoma is one of the most common deadly cancers, and robust biomarkers are still needed, e.g. to predict survival and treatment efficiency. Here, protein expression analysis of one hundred eleven melanoma lymph node metastases using high resolution mass spectrometry is coupled with in-depth histopathology analysis, clinical data and genomics profiles. This broad view of protein expression allowed to identify novel candidate protein markers that improved prediction of survival in melanoma patients. Some of the prognostic proteins have not been reported in the context of melanoma before, and few of them exhibit unexpected relationship to survival, which likely reflects the limitations of current knowledge on melanoma and shows the potential of proteomics in clinical cancer research.

Tumor-Derived Apoptotic Vesicles: With Death They Do Part

Tumor cells release lipid particles known as extracellular vesicles (EV) that contribute to cancer metastasis, to the immune response, and to thrombosis. When tumors are exposed to radiation or chemotherapy, apoptotic vesicles (ApoVs) are released in abundance as the plasma membrane delaminates from the cytoskeleton. Recent studies have suggested that ApoVs are distinct from the EVs released from living cells, such as exosomes or microvesicles. Depending on their treatment conditions, tumor-released ApoV have been suggested to either enhance or suppress anti-cancer immunity. In addition, tumor-derived ApoV possess procoagulant activity that could increase the thrombotic state in cancer patients undergoing chemotherapy or radiotherapy. Since ApoVs are one of the least appreciated type of EVs, we focus in this review on the distinctive characterization of tumor ApoVs and their proposed mechanistic effects on cancer immunity, coagulation, and metastasis.

Fatty Acid Synthase and Acetyl-CoA Carboxylase Are Expressed in Nodal Metastatic Melanoma But Not in Benign Intracapsular Nodal Nevi

BACKGROUND

Melanoma is a potentially lethal form of skin cancer for which the current standard therapy is complete surgical removal of the primary tumor followed by sentinel lymph node biopsy when indicated. Histologic identification of metastatic melanoma in a sentinel node has significant prognostic and therapeutic implications, routinely guiding further surgical management with regional lymphadenectomy. While melanocytes in a lymph node can be identified by routine histopathologic and immunohistochemical examination, the distinction between nodal nevus cells and melanoma can be morphologically problematic. Previous studies have shown that malignant melanoma can over-express metabolic genes such as fatty acid synthase (FASN) and acetyl-CoA carboxylase (ACC). This immunohistochemical study aims to compare the utility of FASN and ACC in differentiating sentinel lymph nodes with metastatic melanomas from those with benign nodal nevi in patients with cutaneous melanoma.

MATERIALS AND METHODS

Using antibodies against FASN and ACC, 13 sentinel lymph nodes from 13 patients with metastatic melanoma and 14 lymph nodes harboring benign intracapsular nevi from 14 patients with cutaneous malignant melanoma were examined. A diagnosis of nodal melanoma was based on cytologic atypia and histologic comparison with the primary melanoma. All nodal nevi were intracapsular and not trabecular. Immunohistochemistry for Melan-A, S100, human melanoma black 45 (HMB45), FASN, and ACC were performed. The percentage of melanocytes staining with HMB45, FASN, and ACC was determined and graded in 25% increments; staining intensity was graded as weak, moderate, or strong.

RESULTS

All metastatic melanomas tested had at least 25% tumor cell staining for both FASN and ACC. Greater than 75% of the tumor cells stained with FAS in 7/13 cases and for ACC in 5/12 cases. Intensity of staining was variable; strong staining for FASN and ACC was observed in 69% and 50% of metastatic melanoma, respectively. HMB45 was negative in 40% of nodal melanoma cases all of which stained with FASN and ACC. Capsular nevi were uniformly negative for FASN, ACC, and HMB45 immunoreactivity.

CONCLUSIONS

All metastatic melanoma cases involving sentinel lymph nodes were positive for FASN and ACC while no staining was observed in intracapsular nevi. These findings suggest that FASN and ACC could be used as valuable ancillary stains in the distinction between nodal nevi and metastatic melanoma.

Dynamic 18F-FDG PET Lymphography for In Vivo Identification of Lymph Node Metastases in Murine Melanoma

Positron lymphography using ¹⁸F-FDG followed by Cerenkov-guided resection of lymph nodes in healthy mice has previously been introduced by our group. Our aim in this study was to further assess the technique's potential beyond merely localizing sentinel lymph nodes. We now aimed to evaluate the potential of positron lymphography to characterize the nodes with respect to their tumor status in order to identify metastatic lymph nodes. We explored whether metastatic nodes could be distinguished from normal nodes via dynamic ¹⁸F-FDG lymphography, to then be resected under Cerenkov imaging guidance. Methods: A murine melanoma cell line highly metastatic to lymph nodes (B16F10) was implanted subcutaneously on the dorsal hind paw of C57 mice while the tumor-free contralateral leg served as an intraindividual control. A model of reactive lymph nodes after concanavalin A challenge served as an additional control to provide nonmalignant inflammatory lymphadenopathy. Dynamic PET/CT imaging was performed immediately after injection of ¹⁸F-FDG around the tumor or intracutaneously in the contralateral footpad. Furthermore, PET/CT and Cerenkov studies were performed repeatedly over time to follow the course of metastatic spread. In selected mice, popliteal lymph nodes underwent Cerenkov luminescence imaging. Hematoxylin and eosin staining was done to verify the presence of lymphatic melanoma infiltration. Results: Positron lymphography using ¹⁸F-FDG was successfully performed on tumor-bearing and non-tumor-bearing mice, as well as on controls bearing sites of inflammation; the results clearly identified the sentinel lymph node basin and delineated the lymphatic drainage. Significantly prolonged retention of activity was evident in metastatic nodes as compared with controls without tumor. On the basis of these results, the contrast in detection and identification of metastatic lymph nodes was distinct and could be used for guided lymph node resection, such as by using Cerenkov luminescence imaging. However, retention after ¹⁸F-FDG lymphography was also seen in acute inflammatory lymphadenopathy. Conclusion: In a tumor model, significantly longer retention of the radiotracer during ¹⁸F-FDG lymphography was seen in metastatic than nonmetastatic lymph nodes, allowing for differentiation between the two and for selective resection of tumor-bearing nodes using Cerenkov imaging. Inflammation can be better differentiated in a subacute state.

Optical clearing based cellular-level 3D visualization of intact lymph node cortex

Lymph node (LN) is an important immune organ that controls adaptive immune responses against foreign pathogens and abnormal cells. To facilitate efficient immune function, LN has highly organized 3D cellular structures, vascular and lymphatic system. Unfortunately, conventional histological analysis relying on thin-sliced tissue has limitations in 3D cellular analysis due to structural disruption and tissue loss in the processes of fixation and tissue slicing. Optical sectioning confocal microscopy has been utilized to analyze 3D structure of intact LN tissue without physical tissue slicing. However, light scattering within biological tissues limits the imaging depth only to superficial portion of LN cortex. Recently, optical clearing techniques have shown enhancement of imaging depth in various biological tissues, but their efficacy for LN are remained to be investigated. In this work, we established optical clearing procedure for LN and achieved 3D volumetric visualization of the whole cortex of LN. More than 4 times improvement in imaging depth was confirmed by using LN obtained from H2B-GFP/actin-DsRed double reporter transgenic mouse. With adoptive transfer of GFP expressing B cells and DsRed expressing T cells and fluorescent vascular labeling by anti-CD31 and anti-LYVE-1 antibody conjugates, we successfully visualized major cellular-level structures such as T-cell zone, B-cell follicle and germinal center. Further, we visualized the GFP expressing metastatic melanoma cell colony, vasculature and lymphatic vessels in the LN cortex.

Diagnostic utility of neural stem and progenitor cell markers nestin and SOX2 in distinguishing nodal melanocytic nevi from metastatic melanomas

Sentinel lymph node evaluation is a critical component of melanoma staging, and lymph node status provides one of the most powerful predictors of melanoma recurrence and survival. One of the well-known diagnostic pitfalls in melanoma sentinel lymph node evaluation is the presence of nodal melanocytic nevi, which has been demonstrated in up to 26% of lymphadenectomy specimens and specifically in melanoma patients. Melanocytic markers enhance the sensitivity of melanoma detection in sentinel lymph nodes. However, established markers such as anti-melan-A/MART1, S100 protein and SOX10 antibodies cannot discriminate melanoma metastasis from nodal nevi. Recent studies have demonstrated strong expression of neural stem/progenitor cell markers nestin and SOX2 in melanoma. In this study, we tested the diagnostic utility of nestin and SOX2 in differentiating metastatic melanomas from nodal nevi. Twenty-three lymph nodes with metastatic melanomas and 17 with nodal nevi were examined. Of the 23 metastatic melanomas, 18 showed diffuse and strong (3+) nestin, 4 showed rare cells with strong (3+) nestin, and one showed diffuse but faint (1+) nestin staining. Nuclear SOX2 was positive in 13 metastatic melanomas. In contrast, 15 nodal nevi showed no nestin, and 2 showed rare cells with very faint (<1+) nestin staining. SOX2 was negative in 13 nodal nevi. Overall, nestin was strongly expressed in metastatic melanomas (n=22/23; 96%), but not in nodal melanocytic nevi (n=15/17; 88%; P<0.0001). SOX2 was also expressed in metastatic melanomas (n=13/23; 57%) but not in the majority of nodal melanocytic nevi (n=13/16; 81%; P=0.02). In one lymph node harboring metastatic melan-A-negative desmoplastic melanoma, nestin and SOX2 strongly highlighted the infiltrating tumor cells, suggesting the potential clinical value of these two markers in desmoplastic melanoma lymph node biopsies. This study provides evidence that nestin and SOX2 can effectively differentiate nodal melanocytic nevi from metastatic melanomas and serve as powerful diagnostic adjuncts in melanoma staging.

Nanoparticle migration and delivery of Paclitaxel to regional lymph nodes in a large animal model

BACKGROUND

The aim of this study was to demonstrate feasibility of migration and in situ chemotherapy delivery to regional lymph nodes (LN) in a large animal model using an expansile polymer nanoparticle (eNP) delivery system.

STUDY DESIGN

Dual-labeled 50-nm and 100-nm eNP were prepared by encapsulating an IR-813 near-infrared (NIR) fluorescent dye within coumarin-conjugated expansile polymer nanoparticles (NIR-C-eNP). NIR imaging and fluorescent microscopy were used to identify intralymphatic migration of NIR-nanoparticles to draining inguinal or mesenteric LN after injection in swine hind legs or intestine. Nanoparticle-mediated intranodal delivery of chemotherapy was subsequently assessed with Oregon Green paclitaxel-loaded NIR-eNP (NIR-OGpax-eNP).

RESULTS

NIR imaging demonstrated direct lymphatic migration of 50-nm, but not 100-nm, NIR-C-eNP and NIR-OGpax-eNP to the draining regional LNs after intradermal injection in the hind leg or subserosal injection in intestine. Fluorescent microscopy demonstrated that IR-813 used for NIR real-time trafficking colocalized with both the coumarin-labeled polymer and paclitaxel chemotherapy and was identified within the subcapsular spaces of the draining LNs. These studies verify nodal migration of both nanoparticle and encapsulated payload, and confirm the feasibility of focusing chemotherapy delivery directly to regional nodes.

CONCLUSIONS

Regionally-targeted intranodal chemotherapy can be delivered to draining LNs for both skin and solid organs using 50-nm paclitaxel-loaded eNP.

Identification of nodal metastases in melanoma using sox-10

The presence of S100-positive dendritic cells hinders the identification of isolated melanoma tumor cells and micrometastases in sentinel lymph nodes. Sox-10, a transcription factor that plays an important role in schwannian and melanocytic cell development, is not expressed in dendritic cells. We investigated the diagnostic utility of Sox-10 in the identification of metastases in sentinel and nonsentinel lymph nodes for melanoma. We examined the expression pattern of Sox-10, as compared with S100, Melan-A, and HMB-45 in 93 lymph nodes (40 originally reported as positive and 53 originally reported as negative for metastasis) from 33 sentinel lymph node biopsies and regional lymphadenectomies. Sox-10 and S100 both highlighted metastases in 43 of 43 (100%) positive lymph nodes identified in this study; however, Sox-10 immunohistochemical staining significantly improved the detection of nodal metastases. The nuclear staining of Sox-10 promoted improved distinction between heavily pigmented melanophages and melanocytic metastases in 3 positive lymph nodes. In 2 lymph nodes, Sox-10 was critical in distinguishing S100-positive atypical nodal dendritic cells from tumor cells. Also, Sox-10 significantly improved the identification of micrometastases and isolated tumor cells as compared with S100 in 10 positive lymph nodes. Most importantly, Sox-10 identified micrometastases in 2 lymph nodes, originally reported as negative on S100, Melan-A, and HMB-45 immunostains. Therefore, Sox-10 is a comparable marker to S100 in identifying nodal metastases in melanoma and is especially useful in the setting of lymph nodes with heavily pigmented metastases, numerous S100-positive nodal dendritic cells, micrometastases, and isolated tumor cells.

Use of fluorescence in situ hybridization (FISH) to distinguish intranodal nevus from metastatic melanoma

With the increase in sentinel lymph node biopsies in melanoma patients, pathologists are frequently confronted with small deposits of morphologically bland melanocytes in the node, which occasionally cannot be readily classified as benign nodal nevi or melanoma. As most melanomas harbor characteristic chromosomal aberrations which can be used to distinguish them from benign nevi, we used fluorescence in-situ hybridization (FISH) with markers for 3 regions on chromosome 6 and 1 on chromosome 11 to determine the presence of chromosomal aberrations in sentinel lymph node specimens with small foci of melanocytes that had been diagnosed as metastatic melanoma or nodal nevi by histopathology. Fifty-nine tissue samples from 41 patients (24 lymph node metastases, 17 with nodal nevi, and 18 of the available corresponding primary melanomas) were analyzed by FISH. Twenty of 24 (83%) cases diagnosed as metastatic melanoma showed aberrations by FISH. Of the 4 negative cases, 3 were unequivocal melanoma metastases, whereas 1 on re-review was histopathologically equivocal. Of the 17 nodal nevi, 1 (6%) also showed aberrations by FISH, whereas the remainder was negative. Multiple aberrations were present in the positive case, some of which were also found in the corresponding primary tumor, suggesting that this case represents a deceptively bland melanoma metastasis that had been misclassified by histomorphology. Our data indicate that FISH is a useful adjunct tool to traditional methods in the diagnostic workup of deposits of melanocytes in lymph nodes that are histopathologically ambiguous.

Diagnostic utility of IMP3 in segregating metastatic melanoma from benign nevi in lymph nodes

Depending on the Breslow depth of the primary melanoma, sentinel lymph node biopsy is considered as standard of care for the staging of cutaneous melanoma, and is one of the most important prognostic factors. The histologic analysis of these specimens becomes difficult to interpret when benign intranodal nevic cells mimic metastases. Insulin-like growth factor-II messenger RNA (mRNA)-binding protein-3 (IMP3), also known as K homology domain-containing protein overexpressed in cancer or L523S, is a member of the insulin-like growth factor-II mRNA-binding protein family and has been shown to have diagnostic utility in distinguishing cutaneous melanoma from benign nevi. In this study, 43 sentinel lymph node biopsy specimens, including 13 with benign intranodal nevi and 30 with metastatic melanoma (two cases containing both benign nevi and metastatic melanoma), from 41 patients were immunohistochemically analyzed with a monoclonal antibody against IMP3. None of the benign intranodal nevi expressed IMP3, whereas 21 out of 30 (70%) of the lymph nodes containing metastatic melanoma did. It seems that IMP3 is helpful in distinguishing benign intranodal nevi from metastatic melanoma in sentinel lymph node biopsy specimens, and could be a valuable diagnostic adjunct in sentinel lymph node biopsy assessment in which questions arise as to the malignancy of the melanocytes present.

Serological reagents for the immunohistochemical analysis of melanoma metastases in sentinel lymph nodes

For the immunohistochemical analysis of melanoma, various serological reagents are available. Melanocyte differentiation markers are reactive with cells and tumors of melanocytic lineage. HMB45 to gp100 has been the most commonly used melanocyte differentiation marker. Recently it was complemented by reagents such as antibodies to Melan-A/MART-1 and tyrosinase. Other reagents, whose reactivity is not strictly confined to melanocyte differentiation antigens, are also commonly used. Among them, the most prominent is S100. Other reagents are D5 to MITF or PNL-2. The properties of these reagents are presented, and their usefulness as markers in the setting of metastatic melanoma in sentinel lymph nodes is discussed.

Giant bathing trunk naevus with lymphadenopathy and unusual pathology

Giant congenital melanocytic naevi remain a challenge to clinicians and histopathologists with respect to observation for malignant change and interpretation of histology findings, respectively. We report a 5-year-old boy with a giant bathing trunk naevus who, after multiple previous skin biopsies, developed lymphadenopathy. Biopsy from the lymph nodes demonstrated collections of naevomelanocytes within the lymph node. Interpretation of these findings and subsequent management is discussed.

Histological features of melanoma sentinel lymph node metastases associated with status of the completion lymphadenectomy and rate of subsequent relapse

BACKGROUND

The current recommendation for patients with cutaneous melanoma and a positive sentinel lymph node (SLN) biopsy is a completion lymph node dissection (CLND). This study sought to define a population of SLN-positive patients, based on their histological pattern of SLN metastases, who may not require CLND.

METHODS

All patients with SLN-positive cutaneous melanoma who underwent CLND between March 1999 and December 2004 at a single academic institution were enrolled. Metastatic deposits in the SLN were categorized by their histological zone of involvement (subcapsular, parenchymal and/or sinusoidal). Logistic regression was used to examine the effect of SLN zone, size of nodal metastases, and other histological factors on CLND positivity. Kaplan-Meier and Cox models were used to study disease recurrence.

RESULTS

A total of 127 patients were included, and 15.8% had positive non-sentinel nodes. In adjusted analyses, the size of the largest tumor deposit in the SLN was the only factor associated with CLND status. No patients with a tumor deposit <or=0.20 mm had a positive CLND. Although a specific zone of tumor involvement was not predictive of CLND status, involvement of all three zones was independently associated with increased recurrence. Size of the largest tumor deposit was also associated with recurrence, with no recurrences in patients with nodal deposits <or=0.20 mm.

CONCLUSION

Histologic features of tumor metastases in positive SLN may be useful in defining a population of patients who may be spared CLND and a group at high risk of recurrence.