Metastases of malignant melanoma simulating soft tissue sarcoma. A clinico-pathological, light- and electron microscopic and immunohistochemical study of 21 cases

Multiple giant cutaneous metastasis and ileal intussusception from an unknown melanoma: A case report

Intestinal intussusception is one of the most common causes of intestinal obstruction in children; however, the incidence in adults is lower, and is caused by tumors in the majority of cases. Melanoma of the gastrointestinal tract is relatively rare, with only a small number of cases having been reported. The majority of cases occur as metastasis from cutaneous primary lesions, and the small bowel is the most common location of melanoma metastases in the gastrointestinal tract. The present study describes the case of a 47-year-old male patient with multiple soft tissue tumors, the largest one located in the left gluteal region, measuring 14x15x20 cm. This tumor was biopsied and a differential diagnosis was made between clear cell sarcoma and melanoma. The patient was evaluated by a dermatologist, without identifying any skin lesions compatible with cutaneous melanomas and was admitted to the emergency room due to an ileo-ileal intussusception. The results of the pathological analysis confirmed the final diagnosis of melanoma. On the whole, these lesions are usually diagnosed with the onset of symptoms, presenting an ominous prognosis.

An unusual case of metastatic melanoma in subcutaneous tissue presenting as a solitary cystic mass with fluid levels

Malignant melanoma is a common and often aggressive neoplasm of the skin arising from melanocytes. Metastatic melanoma is known for its diverse clinical manifestations, and can present with atypical features prior to diagnosis of the primary lesion, which can pose a diagnostic challenge. We report a rare case of metastatic melanoma in a 67 year-old male who presented with a painless, enlarging mass in the right axilla over a 4 week period. Ultrasound and magnetic resonance imaging (MRI) scans revealed a well-defined solitary, cystic appearing lesion in the right axilla with a distinct fluid-fluid level. An ultrasound guided biopsy of the lesion diagnosed a metastatic melanoma. While haemorrhagic distant metastases are a well-recognised complication of malignant melanoma, particularly in the brain and lung, soft tissue metastases presenting with fluid-fluid levels is not well described in the literature. The case highlights the importance of considering the differential of melanoma metastasis when encountered with such a lesion and importance of ultrasound guided biopsy for histopathological confirmation, as the imaging features can mimic that of a haemorrhagic soft tissue sarcoma, the management of which differs substantially from that of melanoma.

Neurosarcomatous amelanotic transformation of malignant melanoma presenting as malignant periopheral nerve sheath tumor: Rare case report

RATIONALE

Malignant melanoma (MM) is notorious for its remarkable morphological variation and aberrant histopathological patterns. In addition, Malignant Periopheral Nerve Sheath Tumor (MPNST) is an uncommon but aggressive soft tissue sarcoma. Because of the common embryological origin of melanocytes and Schwann cells in the neural crest, discriminating between a particular type of MM and MPNST can be difficult, particularly when they are amelanotic. Our goal is to increase awareness among clinicians of the rare variations of MM and the importance of medical history in improving the accuracy of the final clinical diagnosis.

PATIENT CONCERNS

A 68-year-old man was admitted to the hospital due to pain in his right ankle, which had persisted for 8 months, along with swelling for 4 months. Medical history revealed delayed healing of right plantar for 5 years after a traumatic injury.

DIAGNOSES

The ankle mass was initially diagnosed as MPNST through biopsy. After reviewing the patient's medical history and receiving the final pathological report following amputation, we have revised the diagnosis to metastatic amelanotic desmoplastic melanoma in the ankle part and lentigo maligna melanoma in the plantar part. This is due to both lesions displaying positive markers or mutated genes in immunohistology and Gene Mutation Detection, indicating homology between the 2 tumors.

INTERVENTIONS

Due to the malignant characteristics of the tumor and the patient's wishes, amputation of the right lower leg was carried out.

OUTCOMES

Subsequently, the patient was treated with interferon-γ and immunosuppressant PD-1 inhibitor, and survived for 1 year after amputation.

LESSONS

Clinical data, immunohistochemisty biomarkers and genes detection results can serve as valuable evidence for pathologists and clinicians in identifying the disease process. Collaborative efforts between clinicians and scientists are crucial in order to identify specific markers that can effectively differentiate between the 2 tumors, thereby enhancing the conclusiveness of the diagnosis.

Clinical Impact of Prospective Whole Genome Sequencing in Sarcoma Patients

With more than 70 different histological sarcoma subtypes, accurate classification can be challenging. Although characteristic genetic events can largely facilitate pathological assessment, large-scale molecular profiling generally is not part of regular diagnostic workflows for sarcoma patients. We hypothesized that whole genome sequencing (WGS) optimizes clinical care of sarcoma patients by detection of diagnostic and actionable genomic characteristics, and of underlying hereditary conditions. WGS of tumor and germline DNA was incorporated in the diagnostic work-up of 83 patients with a (presumed) sarcomas in a tertiary referral center. Clinical follow-up data were collected prospectively to assess impact of WGS on clinical decision making. In 12/83 patients (14%), the genomic profile led to revision of cancer diagnosis, with change of treatment plan in eight. All twelve patients had undergone multiple tissue retrieval procedures and immunohistopathological assessments by regional and expert pathologists prior to WGS analysis. Actionable biomarkers with therapeutic potential were identified for 30/83 patients. Pathogenic germline variants were present in seven patients. In conclusion, unbiased genomic characterization with WGS identifies genomic biomarkers with direct clinical implications for sarcoma patients. Given the diagnostic complexity and high unmet need for new treatment opportunities in sarcoma patients, WGS can be an important extension of the diagnostic arsenal of pathologists.

A rare case of intranodal hemorrhagic spindle cell tumor with amianthoid fibers presenting as a suspicious lump in the groin

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Hemorrhagic spindle cell tumor with amianthoid fibers is extremely rare.

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The present case adds to the very limited data available on this entity.

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The tumor in the present case reached a relatively large size and raised clinical suspicion for lymphoma.

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This tumor is a mimicker for many benign and malignant conditions.

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This tumor must be considered to avoid the misinterpretation as primary malignant spindle cell lesion or metastasis.

Introduction

Intranodal hemorrhagic spindle cell tumor with amianthoid fibers is extremely rare.

Presentation of the case

Herein, we present the case of a 58-year-old man with a 2-year history of painless left inguinal swelling. On physical examination, the mass was large, fixed, hard, and non-tender, suggesting a lymph node pathology. The mass had increased slightly in size after a short course of antibiotic treatment. The surgeon decided to perform an excisional biopsy of the left inguinal lymph node. The lesion was intraoperatively hard and suspicious for malignancy. The gross examination revealed a relatively large well-circumscribed mass with a whitish, hard, cut surface. The histomorphological and immunohistochemical findings were consistent with intranodal hemorrhagic spindle cell tumor with amianthoid fibers. There was no evidence of recurrence at 4 years post surgery.

Discussion

The present case adds to the very limited data available on this rare entity.

Conclusion

Intranodal hemorrhagic spindle cell tumor with amianthoid fibers can be a diagnostic pitfall both clinically and histopathologically. It can reach large sizes and be clinically and grossly suspicious for lymphoma. Clinicians must be made aware that such an entity exists.

Amelanotic Signet Ring Cell Melanoma Presenting as Breast Lump- A Diagnostic Conundrum

Amelanotic signet ring cell melanoma is one of the rare variants of malignant melanoma. Here we are presenting a case of a 58-year-old female with chief complaints of swelling in the left sternal region/breast, and right cervical region. Contrast Enhanced CT scan showed the two well circumscribed lobular mass lesions with central necrosis in the left breast. The radiologist opined the lesions as intramammary nodes. Biopsy from the larger breast mass lesion showed a tumour with cells arranged in discohesive pattern less with hetrogenos morphology. These tumour cells had a predominantly signet ring morphology along with markedly pleomorphic tumour cells and giant cells. These tumour cells were negative for pan CK and positive for S100, HMB45. So the case was diagnosed as metastatic amelanotic malignant melanoma with signet ring morphology.

Single sternal metastasis due to malignant melanoma with unexpected long-term survival: a case report

Metastases from melanoma have a very poor prognosis for the patient. Single metastatic lesions in the sternum due to melanoma are extremely rare. A rare case of a presternal mass in a 56-year-old patient who had undergone excision for malignant melanoma is presented. Review of the patient’s history and surgical resection of a single metastatic soft tissue lesion offer the best chance of long-term survival.

Metastatic amelanotic melanoma with occult primary masquerading as sarcoma

Malignant melanoma with occult primary is extremely rare. It is found that survival is almost same or even better than the melanomas with known primary site. Surgeons should have a high index of suspicion when a patient presents like sarcoma which bleeds profusely when planning for excision. Here, is an unusual case of young adult which presented initially with granulomatous lymphandenitis in axilla with primary suspicion of tuberculosis, later turning out to be sarcoma on FNAC and MRI. On immunochemistry (IHC), the final diagnosis of amelanotic melanoma was made and further workup did not show up any primary site of origin.

Update on Molecular Pathology of Cutaneous Melanocytic Lesions: What is New in Diagnosis and Molecular Testing for Treatment?

In this article, we give an update on recent findings regarding molecular pathology in cutaneous melanocytic tumors. The focus lies on use of genetics in the diagnosis of distinct subtypes of spitzoid tumors that are often characterized by specific phenotypic–genotypic alterations that can frequently be recognized by adequate histological examination. Typical illustrating cases are given in order to increase recognition of these lesions in daily dermatopathology practice. New molecular findings in the pathogenesis of congenital melanocytic tumors and neurocutaneous melanosis are reviewed. In addition, use of mutation analysis in the differential diagnosis of melanoma metastasis is discussed. Finally, application of mutation analysis in targeted therapy in advanced melanoma with advantages of new techniques such as next generation sequencing is described.

Cytopathologic diagnosis of Kaposi sarcoma in unusual clinical settings

INTRODUCTION

Kaposi sarcoma (KS) is a rare disease that presents as 1 of 4 distinct clinicopathologic subtypes; however, it may present in populations outside those normally encountered. In such cases, it will be important to consider KS in the differential diagnosis, as it may mimic other neoplastic and non-neoplastic entities.

MATERIALS AND METHODS

We describe 2 cases of KS, 1 in a patient not clinically fitting any of the 4 subtypes and the other in a patient with atypical presentation in human immunodeficiency virus (HIV)-associated disease. The first is an 81-year-old African American (AA) woman with a history of KS of the leg, who presented with groin lymphadenopathy and the second is a 42-year-old AA man with a known history of HIV infection, no skin lesions, and new axillary lymphadenopathy.

RESULTS

Fine-needle aspiration of the groin and axillary lymph node, respectively, showed atypical spindle cells in a lymphoplasmacytic background. The spindle cells were positive for human herpesvirus-8 on the cell block and subsequent lymph node excision. In patients with HIV infection, in addition to reactive and lymphoproliferative processes, KS should be considered. In the former case, the demographic of an elderly AA woman without immunosuppression would not cause concern for systemic KS, but for a metastatic tumor or lymphoma.

CONCLUSIONS

Cytology is a helpful tool in narrowing the differential diagnosis for spindle cell lesions. With a diagnosis of KS, clinicians would be able to query the clinical history for a possible etiology, such as HIV, and exclude the possibility of metastatic disease.

Soft Tissue Pseudosarcomas

Soft tissue pathology is one of the most challenging areas of diagnostic pathology, not only because of the morphologic diversity of such lesions, but also because of their rarity and pathologists' subsequent lack of exposure to these tumors. Many lesions mimic malignant mesenchymal neoplasms, collectively referred to as "pseudosarcomas." The list of proliferations that can simulate a sarcoma is extensive and heterogeneous. This review addresses malignant, nonmesenchymal neoplasms; mesenchymal neoplasms that histologically mimic sarcomas but are benign; and benign reactive soft tissue lesions that are neither neoplastic nor malignant, but have worrisome clinical and/or morphologic features.

Spindle cell melanocytic lesions--part I: an approach to compound naevoidal pattern lesions with spindle cell morphology and Spitzoid pattern lesions

Melanocytic lesions show great morphological diversity in their architecture and the cytomorphological appearance of their composite cells. Whereas functional melanocytes reveal a dendritic cytomorphology and territorial isolation, lesional naevomelanocytes and melanoma cells typically show epithelioid, spindled or mixed cytomorphologies and a range of architectural arrangements. Spindling is common to melanocytic lesions, and may be either a characteristic feature or a divergent appearance. The presence of spindle cells may mask the melanocytic nature of a lesion, and is often disconcerting, either because of its infrequent appearance in a particular lesion or its interpretation as a dedifferentiated phenotype. Spindle cell melanocytic lesions follow the full spectrum of potential biological outcomes, and difficulty may be experienced judging the nature of a lesion because of a lack of consistently reliable features to predict biological behaviour. Over time, recognition of numerous histomorphological features that may portend a more aggressive lesion have been identified. However, the translation of these features into a diagnostic entity requires a gestalt approach. Although most spindle cell melanocytic lesions can reliably be resolved with this standard approach, problem areas do exist and cause no end of grief to the surgical pathologist or dermatopathologist. In this review, the authors present their algorithmic approach to spindle cell melanocytic lesions and discuss each entity in turn, in order to (1) model a systematic approach to such lesions, and (2) provide familiarity with those melanocytic lesions that either typically or occasionally display a spindled cytomorphology.

Spindle cell melanocytic lesions: part II—an approach to intradermal proliferations and horizontally oriented lesions

Melanocytic lesions show great morphological diversity in their architecture and the cytomorphological appearance of their composite cells. Whereas functional melanocytes show a dendritic cytomorphology and territorial isolation, lesional nevomelanocytes and melanoma cells typically show epithelioid, spindled or mixed cytomorphologies, and a range of architectural arrangements. Spindling is common to melanocytic lesions, and may either be a characteristic feature or a divergent appearance. The presence of spindle cells may mask the melanocytic nature of a lesion, and is often disconcerting, either due to its infrequent appearance in a particular lesion or its interpretation as a dedifferentiated phenotype. Spindle cell melanocytic lesions follow the full spectrum of potential biological outcomes, and difficulty may be experienced judging the nature of a lesion due to a lack of consistently reliable features to predict biological behaviour. Over time, recognition of numerous histomorphological features that may portend a more aggressive lesion have been identified; however, the translation of these features into a diagnostic entity requires a gestalt approach. Although most spindle cell melanocytic lesions may reliably be resolved through this standard approach, problem areas do exist for the surgical pathologist or dermatopathologist. With this review (part II of II), we complete our discussion of spindle cell melanocytic lesions, in order to: (1) model a systematic approach to such lesions; and (2) provide familiarity with those melanocytic lesions which either typically or occasionally display a spindled cytomorphology.

Could it still be malignant melanoma or just a poorly differentiated neoplasm?

The present case, characterised by an aggressive and poorly differentiated skin malignancy, contributes to a wider discussion on such tumours. Despite repeated histological examinations, including immunohistochemistry, and thorough radiological investigation, diagnosis of melanoma was not easy.

Fine-needle aspiration biopsy of metastatic malignant melanoma resembling a malignant peripheral nerve sheath tumor

We report a case of metastatic malignant melanoma resembling a malignant peripheral sheath tumor, which posed a significant diagnostic challenge. The patient is a 76-year-old male, who presented in the emergency room with bilateral chest pain exacerbated by inspiration. The pain was present for 3 week and was not exacerbated by physical exercise. The diagnostic workup revealed bilateral parenchymal pulmonary infiltrates. The CT-scan guided fine-needle aspiration and the core biopsies of the largest pulmonary lesion revealed high-grade spindle cell neoplasm with individual cell apoptosis and necrosis. The immunohistochemical profile on the cell block showed that the cells are positive for Vimentin. The S-100 stain showed only focal positivity. The immunohistochemical stains for HMB45, Melan A, pancytokeratin, and smooth muscle actin were negative. Five years ago the patient was diagnosed with melanoma on the back with Clark level of IV. The melanoma was excised with clear margins and sentinel lymph nodes were negative. Careful examination of patient's previous slides revealed an area of spindle cell melanoma adjacent to a nodular type melanoma. Based on the patient's previous history, current clinico-pathologic presentation and immunohistochemical profile, the diagnosis of metastatic malignant melanoma resembling peripheral nerve sheath tumor was favored over the diagnosis of metastatic malignant spindle cell neoplasm of unknown primary site, which by itself is very rare clinical scenario.

Differential expression of S100 protein subtypes in malignant melanoma, and benign and malignant peripheral nerve sheath tumors

BACKGROUND

Desmoplastic melanoma (DM) may simulate various benign and malignant lesions, including benign peripheral nerve sheath tumors (BPNSTs) and malignant peripheral nerve sheath tumors (MPNSTs). The latter case is diagnostically challenging because DM generally show only S100 protein expression but no reaction to melanocytic markers. S100 family of proteins consists of over 20 members. We report on S100 subtypes in malignant melanomas (MMs), and BPNSTs and MPNSTs to investigate differential expression.

DESIGN

S100A1, S100A2, S100A4, S100A6 and S100B immunostains were performed on 80 MMs including conventional and desmoplastic types, 86 BPNSTs and 77 MPNSTs.

RESULTS

S100A1 expression was seen in > 91% of MMs in a diffuse reaction, whereas BPNSTs showed focal or no reaction. Sixteen percent of MPNSTs focally expressed S100A1 except for one case with diffuse reaction. S100A2 staining was negative or focal in all three groups whereas S100A4 reaction was variable in all three. S100A6 was diffusely expressed in MMs, BPNSTs and MPNSTs. S100B was stained diffusely in MMs and BPNSTs, but its reaction was observed in 30% of MPNSTs in a focal fashion.

CONCLUSION

S100A1 expression was diffuse in most of MMs but absent or focal in BPNSTs and MPNSTs. This may be helpful to distinguish between the two entities.

Atypical fibroxanthoma

Atypical fibroxanthoma (AFX) is a nodular dermal ulcerative lesion with a favorable prognosis. AFX most commonly occurs on sun-exposed skin in elderly individuals. AFX is characterized by its association with ultraviolet radiation, not only from a clinical aspect, but also from a molecular aspect. Making a diagnosis of AFX is challenging, and it is important to differentiate it from squamous cell carcinoma and malignant melanoma. Histological features and combined immunohistochemical markers are necessary for a definitive diagnosis (i.e., an absence of immunostaining for cytokeratins, S100 and HMB45 in AFX is helpful for excluding both squamous cell carcinoma and malignant melanoma). AFX, as well as MFH (malignant fibrous histiocytoma), is a fibrohistiocytic lesion with myofibroblastic differentiation. AFX is considered to be a different lesion from MFH. AFX and MFH might share the same pathway which determines their morphology. However, they may have different pathways in development which determine their biological behavior.

Divergent differentiation in malignant melanomas: a review

The aim of this review was to document and discuss diagnostic problems associated with divergent differentiation ('metaplastic change') in malignant melanomas, defined as the development in these tumours of morphologically, immunohistochemically and/or ultrastructurally recognizable non-melanocytic cell or tissue components. Types of divergent differentiation reported in malignant melanoma include: fibroblastic/myofibroblastic, Schwannian and perineurial, smooth muscle, rhabdomyosarcomatous, osteocartilaginous, ganglionic and ganglioneuroblastic, neuroendocrine and probable epithelial. Divergent differentiation is certainly a rare phenomenon and, when it occurs, can be missed by unwary pathologists and lead to diagnostic uncertainty. A carefully chosen immunohistochemical panel and the input of electron microscopy can help to clarify the nature of the cellular differentiation of these tumours and lead to a correct final diagnosis. The clinical significance of such aberrations is uncertain, nor are the underlying mechanisms as yet well defined.

Immunohistochemical staining of CD10 in atypical fibroxanthomas

BACKGROUND

The histologic diagnosis of atypical fibroxanthoma (AFX) may be difficult at times with a differential diagnosis including spindle cell/desmoplastic melanoma and a poorly differentiated squamous cell carcinoma (SCC). While there are immunohistochemical stains that may be used to support a diagnosis of either melanoma or carcinoma, the diagnosis of AFX tends to be one of exclusion.

METHODS

A total of 35 cases including 16 AFXs, 10 poorly differentiated SCCs and nine spindle cell/desmoplastic melanomas were stained with the antibody against CD10.

RESULTS

There was strong (3+) diffuse expression of CD10 in 15/16 (94%) AFXs, weak (1+) to moderate (2+) patchy expression of CD10 in 5/10 (50%) SCCs and weak (1+) expression of CD10 in 3/9 (33%) spindle cell/desmoplastic melanomas.

CONCLUSION

CD10 expression is helpful in distinguishing between AFXs, carcinomas and melanomas and will be useful in a panel of antibodies when distinguishing between these entities.

Malignant melanoma in the 21st century, part 1: epidemiology, risk factors, screening, prevention, and diagnosis

Malignant melanoma is an aggressive, therapy-resistant malignancy of melanocytes. The incidence of melanoma has been steadily increasing worldwide, resulting in an increasing public health problem. Exposure to solar UV radiation, fair skin, dysplastic nevi syndrome, and a family history of melanoma are major risk factors for melanoma development. The interactions between genetic and environmental risk factors that promote melanomagenesis are currently the subject of ongoing research. Avoidance of UV radiation and surveillance of high-risk patients have the potential to reduce the population burden of melanoma. Biopsies of the primary tumor and sampling of draining lymph nodes are required for optimal diagnosis and staging. Several clinically relevant pathologic subtypes have been identified and need to be recognized. Therapy for early disease is predominantly surgical, with a minor benefit noted with the use of adjuvant therapy. Management of systemic melanoma is a challenge because of a paucity of active treatment modalities. In the first part of this 2-part review, we discuss epidemiology, risk factors, screening, prevention, and diagnosis of malignant melanoma. Part 2 (which will appear in the April 2007 issue) will review melanoma staging, prognosis, and treatment.

Unusual variants of malignant melanoma

A potential diagnostic pitfall in the histologic assessment of melanoma is the inability to recognize unusual melanoma variants. Of these, the more treacherous examples include the desmoplastic melanoma, the nevoid melanoma, the so-called 'minimal-deviation melanoma,' melanoma with prominent pigment synthesis or 'animal-type melanoma,' and the malignant blue nevus. Also problematic are the unusual phenotypic profiles seen in vertical growth phase melanomas; these include those tumors whose morphological peculiarities mimic cancers of nonmelanocytic lineage and those melanomas that express aberrant antigenic profiles not commonly associated with a melanocytic histogenesis. Metaplastic change in melanoma, balloon cell melanoma, signet-ring cell melanoma, myxoid melanoma, small cell melanoma and rhabdoid melanoma all have the potential to mimic metastatic and primary neoplasms of different lineage derivations. Abnormal immunohistochemical expression of CD 34, cytokeratins, epithelial membrane antigen, and smooth muscle markers as well as the deficient expression of S100 protein and melanocyte lineage-specific markers such as GP100 protein (ie HMB-45 antibody) and A103 (ie Melan-A) also present confusing diagnostic challenges. In this review, we will discuss in some detail certain of these novel clinicopathologic types of melanoma, as well as the abnormal phenotypic expressions seen in vertical growth phase melanoma.

Monster cells in malignant melanoma

Cells with significantly enlarged nuclei have been described in basal cell carcinomas, dermatofibromas, and pleomorphic fibromas, to name a few. These cells are typically visible using low power microscopy and have been termed "pleomorphic" or "monster cells." They have not been previously described in cutaneous melanomas. We sought to determine the prevalence of monster cells in otherwise conventional biopsies of primary cutaneous melanomas and its association with other histopathologic features of this malignancy. Ninety-nine superficial spreading melanomas, nodular melanomas, and acral lentiginous melanomas/lentigo malignas were retrospectively evaluated for the presence of monster cells, multinucleated giant cells, ulceration, inflammation, and depth of invasion (Breslow level). Thirteen cases of melanoma containing monster cells were found. A statistically significant association was noted between the presence of these cells, the histologic subtype of nodular melanoma (P = 0.0125), ulceration (P = 0.0127), the depth of invasion (P = 0.0103), and the presence of multinucleated giant cells (P = 0.0016). The finding of monster cells is not an uncommon occurrence and is seen more often in nodular melanomas.

Malignant peripheral nerve sheath tumour-like primary cutaneous malignant melanoma

Malignant melanoma is known for its protean cytomorphological features, architectural patterns, and stromal changes, in addition to its ability to mimic various benign and malignant non-melanocytic tumours. Anecdotal cases of metastatic malignant melanoma simulating soft tissue sarcomas have been reported. Interestingly, this mimicry is more often seen in recurrent lesions and metastatic deposits. This report describes a case of a primary spindle cell cutaneous malignant melanoma with a prominent neural-like fascicular pattern and nuclear palisading, simulating a conventional malignant peripheral nerve sheath tumour (MPNST). Clinical, microscopic, and immunohistochemical features of the different entities included in the differential diagnosis of cutaneous spindle cell malignant tumours, such as MPNST, atypical fibroxanthoma, and spindle cell squamous cell carcinoma are discussed. Of note, the presence of an atypical epidermal or junctional component, cell pigmentation, and cell nesting, in addition to diffuse and strong reactivity for S-100 protein and other melanocytic markers, are helpful in the diagnosis of these troublesome lesions.

Cellular schwannoma: report of a case diagnosed intraoperatively with the aid of cytologic imprints

The diagnosis of cellular schwannoma in intraoperative consultation is difficult because of the hypercellularity and deep location, which may lead to errors. The recognition of cytologic features together with the histological appearance are of great importance to make the correct diagnosis. An accurate diagnosis of this variant of schwannoma is important because other spindle cell tumors display differences in treatment and clinical behavior. We report a demonstrative case of cellular schwannoma arising in retroperitoneum of a 52-yr-old woman in which the cytologic imprints were useful to make an accurate diagnosis intraoperatively. Briefly, the differential diagnosis is discussed.

PNL2, a new monoclonal antibody directed against a fixative-resistant melanocyte antigen

We report the production of a new monoclonal antibody, PNL2, directed against a fixative resistant melanocyte antigen. The analysis of PNL2 immunostaining on a broad range of normal or malignant human tissues and on various melanocytic lesions revealed its high specificity. PNL2 gave a strong cytoplasmic staining of skin and oral mucosae melanocytes, and staining of granulocytes when used at high concentration. PNL2 stained all intra-epidermal nevi irrespective of their histologic type, but common intradermal nevi and the dermal component of compound nevi were largely non-reactive as only scattered nevus cells in the papillary dermis were labeled. PNL2 labeled more than 70% of the neoplastic cells in all primary melanomas irrespective of their histologic type. However, PNL2 did not label desmoplastic melanomas. All metastatic melanomas were also stained but the percentage of labeled cells was occasionally lower than the primary tumor. PNL2, as anti-Melan A and HMB-45 antibodies, stained most of the clear cell sarcoma cells, and a few cells in angiomyolipomas and lymphangioleiomyomatosis. None of the other non-melanocytic lesions tested were labeled. Proteomic approaches showed that the immunoaffinity purified PNL2-binding complexes isolated from melanoma cell lines comprise at least TAP1, Clathrin 17 and prealbumin proteins, but not the gp100 recognized by HMB-45. In conclusion, this new monoclonal antibody, PNL2, is directed against a new fixative resistant melanocyte associated antigen. This antigen is chemically resistant and thus allows immunostaining after melanin bleaching or decalcification. We also demonstrate that it is different from Melan A and from gp100, even if PNL2 and HMB-45 staining patterns are sometimes similar.

Myxoid melanoma: immunohistochemical studies and a review of the literature

Malignant myxoid melanoma (MMM) is a rarely reported variant of malignant melanoma, which can often be confused with other mucin-containing neoplasms. A retrospective study of 3 cases of MMM and a review of the English-language literature was performed. MMM affects an older population and is frequently misdiagnosed. The major pathologic features are atypical spindle cells embedded in a myxoid stroma. Immunohistochemistry analysis of the tumor shows uniform staining of the spindle cells with S-100. In our 3 cases, there were noticeably more mast cells that could be detected with Giemsa stain and with antibody against transforming growth factor. The prognosis appears to be equivalent to other primary melanomas. Diagnosing MMM requires a high index of suspicion. We hypothesize that mast cells and secretion of transforming growth factor beta stimulates fibroblast secretion of mucin, which contributes to the tumor's invasive potential.

Malignant melanoma with a myxoid stroma: a diagnostic pitfall on fine-needle aspiration biopsy

Malignant melanoma (MM), both primary and metastatic, may be associated with a prominent myxoid stromal reaction causing diagnostic confusion on fine-needle aspiration biopsy (FNAB), most often with sarcomas that demonstrate a myxoid stroma, particularly malignant peripheral nerve sheath tumor (MPNST). We present a case of a 32-yr-old man with no past medical history who presented with a unilateral neck mass clinically suspicious for lymphoma. FNAB produced a specimen composed of large sheets of anaplastic cells encased in a myxoid stroma that was S100 and vimentin-positive but HMB-45-negative. A diagnosis of MPNST was made. Excision demonstrated a metastatic MM of unknown primary, with a prominent myxoid stromal reaction. A repeat HMB-45 was again negative. Electron microscopy demonstrated intracytoplasmic melanasomes and cisternae of rough endoplasmic reticulum with intracisternal parallel tubules, confirming the diagnosis. Although HMB-45 is typically negative in both tumors, S100 should be strongly positive in myxoid MM and only focal in MPNST.

Intra-abdominal spindle cell lesions: a review and practical aids to diagnosis

Intra-abdominal spindle cell lesions are uncommon and often present a diagnostic challenge. An important group of such lesions are the gastrointestinal stromal tumours. Other intra-abdominal spindle cell lesions include fibromatosis, various sarcomas-in particular, leiomyosarcoma, liposarcoma, and malignant peripheral nerve sheath tumour-and, in women, endometrial stromal sarcoma. Less common lesions are inflammatory myofibroblastic tumours, the mesenteric spindle cell reactive lesions, retroperitoneal fibrosis, and solitary fibrous tumour. A variety of intra-abdominal tumours of nonmesenchymal origin may have a spindle cell/sarcomatoid morphology; these include sarcomatoid carcinoma, malignant melanoma and, in women, sarcomatoid granulosa cell tumour. Finally, metastatic sarcomas from pelvic or extra-abdominal organs need also be considered. A set of practical aids to the diagnosis of intra-abdominal spindle cell lesions is presented to assist pathologists dealing with such lesions, particularly with regards to the consideration of differential diagnoses.

Microphthalmia transcription factor in the immunohistochemical diagnosis of metastatic melanoma: comparison with four other melanoma markers

The diagnosis of metastatic malignant melanoma (MMM) may be difficult in surgical pathology, often complicated by the unpredictable spread of this tumor and its great variability on histologic evaluation. Traditionally used immunohistochemical markers on melanomas are insufficient because of either a relative lack of specificity (S100 protein) or variably reported sensitivity (HMB45). Information about some newer markers, such as tyrosinase (TYR) and Melan A, is more limited. Recently, based on the study of a small number of tumors, it was suggested that microphthalmia transcription factor (MITF) is 100% sensitive in the identification of metastatic melanoma. In the current study, we compared the diagnostic usefulness of MITF with that of four other markers in 266 cases of conventional metastatic melanomas from different sites, 33 cases of desmoplastic melanomas, and 1 case of melanoma with rhabdoid features. The specificity of MITF was evaluated by using a representative sample of control tumors. Microphthalmia transcription factor with nuclear positivity was seen in 235 of 266 cases of conventional MMM (88%), usually in more than 30% of tumor cells. However, some melanomas had only foci of MITF- and TYR-positive cells, whereas the majority of cells were generally S100 protein-positive. Only 1 of 30 desmoplastic melanomas (3%) had MITF-positive cells, representing epithelioid foci resembling conventional melanoma. Two cases had TYR in a similar pattern; all were HMB45-negative. One metastatic melanoma with rhabdoid features was negative for MITF and other markers except the S100 protein. Half of the S100 protein negative conventional melanomas (6 of 12) were MITF-positive, whereas 4 of 20 (20%) TYR-negative tumors had reactivity for MITF. The percentages of positive cases of MMM (10% or more tumor cells positive) diagnosed with the four other markers in descending order were 90% (S100 protein and TYR), 78% (melan-A), and 66% (HMB45). Microphthalmia transcription factor appeared to be specific, because significant reactivity was not found in 112 carcinomas, 20 lymphomas, 20 angiosarcomas, 20 fibrous histiocytomas, and 20 malignant peripheral nerve sheath tumors. However, positive nuclei were found focally among reactive histiocytes, especially in osteoclasts, epithelioid histiocytes, and sporadic other histiocytes. Microphthalmia transcription factor may be a valuable addition to the marker panel used in diagnosing melanoma, in combination with S100, TYR, and the other markers, but it is not present in cases of desmoplastic melanomas.

Retrospective study of 338 canine oral melanomas with clinical, histologic, and immunohistochemical review of 129 cases

Diagnostic records from 338 canine oral melanomas in 338 dogs received at the Veterinary Medical Diagnostic Laboratory (1992-1999) were reviewed. Of these tumors, 122 plus an additional 7 metastatic melanomas of unknown origin were selected for clinical follow-up, histologic review, and immunohistochemistry. Chow Chow, Golden Retriever, and Pekingese/Poodle mix breeds were overrepresented, whereas Boxer and German Shepherd breeds were underrepresented. There was no gender predisposition and the average age at presentation was 11.4 years. Forty-nine dogs were euthanized due to recurrence or metastasis. The average postsurgical survival time was 173 days. The gingiva and the labial mucosa were the most common sites. Most tumors were composed of either polygonal cells (27 cases, 20.9%), spindle cells (44 cases, 34.1%), or a mixture of the two (polygonal and spindle) (54 cases, 41.9%). Clear cell (3 cases, 2.3%) and adenoid/papillary (1 case, 0.8%) patterns were uncommon. The metastases of 6/6 oral melanomas had morphologic and immunohistochemical features similar to those of the primary tumors. Immunohistochemically, Melan A was detected in 113/122 oral (92.6%) and 5/7 (71.9%) metastatic melanomas. Only 4/163 nonmelanocytic tumors were focally and weakly positive for Melan A. Antibodies against vimentin, S100 protein, and neuron-specific enolase stained 129 (100%), 98 (76%), and 115 (89.1%) of 129 melanomas, respectively. Antibodies against other melanocytic-associated antigens (tyrosinase, glycoprotein 100) did not yield adequate staining. We conclude that Melan A is a specific and sensitive marker for canine melanomas.

Malignant intramuscular forearm tumor with overwhelming squamous element

Squamous cell carcinoma (SCC) arising in the skeletal muscle is rare. A case of a 19-year-old female patient with an intramuscular forearm tumor showing a histopathologically overwhelming squamous element is presented. Microscopic examination revealed the classical features of SCC, including horn pearls, individual cell keratinization and intercellular bridge. A malignant spindle cell component was not detected. Neither evidence of another primary site nor skin lesion over the tumor was found and no metastatic lesion was detected in the 5 years since the appearance of the mass.

Morphological and immunophenotypic variations in malignant melanoma

A variety of cytomorphological features, architectural patterns and stromal changes may be observed in malignant melanomas. Hence, melanomas may mimic carcinomas, sarcomas, benign stromal tumours, lymphomas, plasmacytomas and germ cell tumours. Melanomas may be composed of large pleomorphic cells, small cells, spindle cells and may contain clear, signet-ring, pseudolipoblastic, rhabdoid, plasmacytoid or balloon cells. Various inclusions and phagocytosed material may be present in their cytoplasm. Nuclei may show bi- or multi-nucleation, lobation, inclusions, grooving and angulation. Architectural variations include fasciculation, whorling, nesting, trabeculation, pseudoglandular/pseudopapillary/pseudofollicular, pseudorosetting and angiocentric patterns. Myxoid or desmoplastic changes and very rarely pseudoangiosarcomatous change, granulomatous inflammation or osteoclastic giant cell response may be seen in the stroma. The stromal blood vessels may exhibit a haemangiopericytomatous pattern, proliferation of glomeruloid blood vessels and perivascular hyalinization. Occasionally, differentiation to nonmelanocytic structures (Schwannian, fibro-/myofibroblastic, osteocartilaginous, smooth muscle, rhabdomyoblastic, ganglionic and ganglioneuroblastic) may be observed. Typically melanomas are S100 protein, NKIC3, HMB-45, Melan-A and tyrosinase positive but some melanomas may exhibit an aberrant immunophenotype and may express cytokeratins, desmin, smooth muscle actin, KP1 (CD68), CEA, EMA and VS38. Very rarely, neurofilament protein and GFAP positivity may be seen.

A case of amelanotic spindle-cell melanoma presenting as metastases to breast and axillary lymph node: diagnosis by FNA cytology

Metastatic neoplasms to the breast are relatively rare. Spindle-cell lesions of the breast are also uncommon. Here we present a case of fine-needle aspiration (FNA) of an amelanotic, spindle-cell melanoma metastatic to the breast and axillary lymph node. The patient was a 47-yr-old female who presented with a right breast mass, left axillary adenopathy, and a pigmented skin lesion on the back. FNA of the right breast and left axilla showed malignant, nonpigmented spindle cells that were weakly positive for HMB-45 on immunocytochemistry. The skin biopsy showed a pigmented malignant melanoma with epithelioid features, and also weak positivity for HMB-45. Although malignant melanoma is one of the more common tumors to metastasize to the breast, this is the first known case that showed exclusive spindle-cell morphology. History and physical examination were crucial in making the correct FNA diagnosis. The cytologic differential diagnosis of spindle-cell tumors of breast and the discordant morphology between the primary and metastatic melanotic lesions observed in this case are discussed.

Cutaneous melanoma with myxoid features: twelve cases with differential diagnosis

Substantial myxoid change can occur in malignant melanoma, but its importance in primary disease has not been systematically evaluated. This report describes the clinical, microscopic, histochemical, and immunohistochemical findings in 12 patients with primary cutaneous malignant melanoma with myxoid features. The tumors presented as solitary lesions situated on the limbs (six lesions), trunk (four lesions), and head and neck (two lesions). The patients included six women and six men, whose ages ranged from 26 to 95 years, with a mean of 63 years. Breslow thickness varied from 0.48 mm to more than 12 mm, with a mean of more than 3.2 mm. Clinical follow-up for an average of 22 months showed one local recurrence, but no evidence of metastases yet. In all cases, there was a combination of myxoid and nonmyxoid areas. A minimum of 15% myxoid cross-sectional area was required for inclusion in the study, and up to 80% was observed. The pale blue mucin identified on hematoxylin and eosin staining was sensitive to hyaluronidase and positive for alcian blue in the 10 cases stained. Immunohistochemical staining was positive for S-100 in all 9 cases stained, positive for HMB-45 in 9 (90%) of 10, and negative for cytokeratin in all 9 cases in which myxoid melanoma remained in the block after previous sections. The presence of myxoid stroma did not define a biologically significant subgroup of melanoma. Only in cases with extensive (>50%) myxoid stromal effacement of the melanoma was there a major diagnostic hurdle. The diagnosis of primary cutaneous melanoma with myxoid features was seldom as problematic as metastatic myxoid melanoma. Positive S-100 stains, negative cytokeratin immunohistochemical stains, and hyaluronidase-sensitive alcian blue staining assisted in the diagnosis of this entity.

Metastatic malignant melanoma resembling malignant peripheral nerve sheath tumor: report of 16 cases

We report 16 cases of metastatic malignant melanoma presenting clinically as lymphadenopathy or a soft-tissue mass and histologically resembling malignant peripheral nerve sheath tumor (MPNST). In two cases, the metastatic malignant melanoma was preceded by a primary cutaneous malignant melanoma; in four cases, it presented synchronously with such a tumor; and in 10 cases, there was no evidence of a previous or concomitant malignant skin lesion. Histologically, the tumors were characterized by a malignant-appearing spindle cell proliferation arranged in fascicles, often accompanied by a peritheliomatous growth pattern, alternating hypercellular and hypocellular areas, numerous mitoses, and foci of necrosis. In nine cases, there was residual lymph node tissue. In none of the cases was there evidence of an anatomic connection with a nerve, a coexistent neurofibroma, or the stigmata of neurofibromatosis. Fourteen of the cases showed strong and generally diffuse immunoreactivity for S-100 protein, and five cases showed positivity for HMB-45. Four of eight patients with follow-up information died of the disease. Tumors with a microscopic appearance compatible with MPNST but showing strong diffuse S-100 protein staining and featuring remnants of lymph node may represent metastatic malignant melanomas and should elicit a search for a previous or concomitant tumor in the skin and other sites. The similarities these tumors share with MPNST are probably related to their common neuroectodermal histogenesis.

Malignant granular cell tumor of soft tissue: diagnostic criteria and clinicopathologic correlation

Seventy-three cases of malignant, atypical, and multicentric granular cell tumors of soft tissue were studied to clarify criteria for malignancy and prognostic factors. Six histologic criteria were assessed: necrosis, spindling, vesicular nuclei with large nucleoli, increased mitotic activity (> 2 mitoses/10 high-power fields at 200x magnification), high nuclear to cytoplasmic (N:C) ratio, and pleomorphism. Neoplasms that met three or more of these criteria were classified as histologically malignant; those that met one or two criteria were classified as atypical; and those that displayed only focal pleomorphism but fulfilled none of the other criteria were classified as benign. Hence, 46 cases were classified as histologically malignant, 21 as atypical (3 were multicentric), and 6 as benign (all were multicentric). The patients with benign multicentric and atypical granular cell tumors had no metastases and there were no tumor deaths. In contrast, 11 of 28 patients (39%) with malignant granular cell tumor with follow-up information died of disease at a median interval of 3 years; 8 of 28 (29%) were alive with disease, and 9/28 (32%) were disease free (median intervals, 2 and 7 years, respectively). There were local recurrences in 9 of 28 malignant cases (32%) and metastases in 14 of 28 (50%) (median intervals, each 2 years). Forty-eight cases were studied immunohistochemically; 100% expressed vimentin, 98% S-100 protein, 98% neuron-specific enolase, 69% CD57, and 65% CD68. Alpha-smooth muscle actin, desmin, epithelial membrane antigen (EMA), cytokeratins (with CAM 5.2 and KL-1), chromogranin, and HMB45 were not detected. The proliferative index with Ki67 (MIB 1) was 10-50% in 14 of 25 malignant tumors (56%), and immunostaining for p53 was detected in 50% or more of tumor cells in 17 of 25 (68%); both of these factors were statistically significant with regard to the histologic classification as benign, atypical, or malignant. Ultrastructural examination of 13 benign, atypical, and malignant granular cell tumors showed engorgement of the cytoplasm with complex granules and lysosomes, as well as Schwannian features. By flow cytometric DNA analysis, two of six malignant tumors were aneuploid, two were hyperdiploid, and two were diploid. One atypical tumor was aneuploid and all 11 benign tumors were either diploid (9 cases) or hyperdiploid (2 cases). Statistically significant adverse prognostic factors with regard to survival included local recurrence, metastasis, larger tumor size, older patient age, histologic classification as malignant, presence of necrosis, increased mitotic activity, spindling of tumor cells, vesicular nuclei with large nucleoli, and Ki67 values greater [corrected] than 10%. This study defines clinical and morphologic criteria for malignancy in granular cell tumors and shows that malignant granular cell tumor is a high-grade sarcoma with a high rate of metastases and a short survival.

An immunophenotypic survey of malignant melanomas

An immunohistochemical study of 106 malignant melanoma specimens from 59 patients, using formalin-fixed, paraffin-embedded material, is reported. Negativity for HMB-45 was seen in 11% of specimens. The rate of positivity with CAM 5.2 was 7%. One specimen showed alpha-smooth muscle actin (alpha SMA) positivity. For 11 of the 12 cases in which anomalous immunophenotypes were seen, multiple specimens were available; nine of these showed evidence of an alteration in the immunophenotype between specimens. Comparing the primary tumours with local recurrences and metastases, there was, variously, loss of HMB-45, S-100 protein and NKI/C3 positivity, and acquisition of CAM 5.2 and alpha SMA positivity. In some cases, the change of immunophenotype appeared to occur in a single step. However, one case with six consecutive specimens showed evidence of progressive loss of HMB-45, S-100 protein and NKI/C3 with concomitant gain of CAM 5.2 staining. The implications for the use of immunophenotyping in diagnostic practice are discussed.

Metastatic signet-ring cell melanoma in a patient with an unknown primary tumor. Histologic, immunohistochemical, and ultrastructural findings

Signet-ring cell melanoma is a rare morphologic variant of malignant melanoma. We describe a 27-year-old man with widespread cutaneous and internal metastases of an unknown primary tumor. One skin biopsy specimen and a fine-needle aspirate showed polygonal tumor cells consistent with the diagnosis of metastatic melanoma, but a second skin biopsy specimen revealed neoplastic cells with a signet-ring cell appearance. Both specimens, however, yielded identical immunohistochemical findings. Tumor cells were positive for vimentin and S-100 protein and reacted with the melanoma markers HMB-45 and NKI-C3. Ultrastructural studies revealed abundant intermediate filaments in the cytoplasm of the signet-ring cells. Based on these findings, a diagnosis of metastatic melanoma was made. In this report we describe the fourth case of metastatic signet-ring cell melanoma, and discuss how malignant melanoma may lead to metastases that have divergent morphologic appearances in the same patient.