Myxoid metastases of melanoma: report of three cases and review of the literature

Metastatic melanoma and rare melanoma variants: a review

The histopathological diagnosis of melanoma is fraught with potential pitfalls. In the setting of cutaneous metastatic melanoma, it is important to recognise the various histological patterns that can be encountered from the more common to the rare, including epidermotropic, folliculotropic, naevoid, and blue naevus-like. In addition, melanoma is notorious for phenotypic plasticity. Thus, there are many different subtypes and cytomorphological variations that can be difficult to recognise as melanoma, particularly in the recurrent or metastatic setting. Select melanoma variants including primary dermal, clear cell, plasmacytoid, signet ring cell, small cell, myxoid, rhabdoid, and dedifferentiated melanoma will be discussed, in addition to composite melanocytic neoplasms. This review is intended to remind the practitioner of key concepts of metastatic disease and select rare melanoma variants, while providing practical guidelines for accurate diagnosis.

Fine needle aspiration of malignant melanoma with myxoid features: A case report with molecular analysis

Malignant melanoma with myxoid features (MMM) is a rare melanoma variant in which tumor cells are embedded within a basophilic myxoid stroma. The stromal matrix is composed of acidic mucopolysaccharides, which are thought to be produced by mesenchymal stromal cells in response to melanoma invasion. Interestingly, this myxoid matrix is more often seen in metastasis from a primary tumor that does not have a myxoid stroma. The diagnosis of MMM on fine needle aspiration (FNA) can be confused with other myxoid tumors. Herein, we present a case of MMM diagnosed by FNA of a peri-auricular lymph node in an 89-year-old man with a history of resected malignant melanoma. We describe the clinical, cytohistological, and immunohistochemical findings, and present the unique molecular alterations that were identified. We also discuss the differential diagnosis and potential diagnostic pitfalls associated with MMM.

Melanoma with second myxoid stromal changes after personally applied prolonged phototherapy

Most malignant melanomas are easily diagnosed; however, melanoma is also one of the lesions most frequently reported to mimic other tumors. One of the most difficult patterns to recognize is characterized by prominent myxoid matrix. A case is presented of primary cutaneous melanoma with abundant myxoid matrix in a patient who underwent prolonged phototherapy. Three years before, after getting sunburns, the patient noticed changes of a congenital nevus located in the area of sunburns. It became darker, started to blanch, and grew, with occasional bleeding. Without consulting a physician, the patient applied phototherapy onto the area for 30 months. He used a Bioptron lamp with polarized, polychromatic, incoherent light, at a wavelength from 480 to 3400 nm, without ultraviolet radiation. Clinically, the lesion was unevenly pigmented, ulcerated, covered with hemorrhagic crust, and measuring 3.5 cm in greatest dimension, with a satellite nodule. Multiple metastatic subcutaneous nodules were also found on the scalp and trunk. Histologically, the primary tumor and metastases were composed of nests and pseudotubular formations of polygonal, spindle, and stellate cells embedded in abundant myxoid stroma that comprised more than 80% of the tumor mass. Focally, in the epidermis and papillary dermis, nests of atypical melanocytes and numerous melanophages were observed. Chemotherapy and immunotherapy were administered as suggested by an oncologist. The patient died from distant metastases 6 months after the diagnosis. Although some authors believe that myxoid changes do not seem to alter the behavior of melanoma, it remains an important differential diagnosis issue.

Ungewöhnliche Formvarianten maligner melanozytärer Tumoren

Benign and malignant melanocytic neoplasms are relatively frequent and show a broad morphological heterogeneity. The spectrum of malignant melanomas comprises the four main types, superficial spreading malignant melanoma, nodular malignant melanoma, lentigo-maligna melanoma and acrolentiginous malignant melanoma. In addition the rare spitzoid malignant melanoma, desmoplastic malignant melanoma as well as some unusual variants of malignant melanoma can be distinguished. The latter include nevoid malignant melanoma, a form of malignant melanoma resembling benign melanocytic nevi, animal type malignant melanoma, an atypical melanocytic neoplasm with numerous melanophages and prominent melanosis resembling an atypical epithelioid blue naevus as well as regressive malignant melanoma, and representing a questionably distinct entity, balloon cell and signet-ring malignant melanomas, melanoma types with degenerative clear cell changes, as well as myxoid and osteogenic malignant melanomas that are characterized by unusual stromal changes.

Unusual histologic and clinical variants of melanoma: Implications for therapy

Unusual histologic variants of melanoma may be problematic to the histopathologist. Several of these variants are sufficiently rare that their biologic behavior remains obscure. As identification of some of these melanoma subtypes has specific implications for the therapeutic approach, and as some may mimic other forms of epithelial or mesenchymal neoplasia, their recognition is key to patient management.

Metastatic myxoid melanoma with partial regression of the primary lesion

Myxoid melanoma is a rare variant of malignant melanoma. The diagnostic problems are obviously increased when it presents as amelanotic metastasis in a lymph node. An 82-year-old woman presented a subcutaneous mass in the right axilla. A thorough clinical investigation disclosed a pigmented black lesion on the right forearm. The right axillary lymph nodes and the pigmented lesion were resected. In the lymph nodes, proliferation of tumor cells with an abundant mucous substrate was noted. The cells proliferated in a variable pattern, and there were no melanin granules detected on hematoxylin-eosin-stained sections. However, we found melanin granules in the tumor cells observed under electron microscopy. In the pigmented lesion of the right forearm, there were small clusters of tumor cells with melanin granules, suggesting malignant melanoma. In the present case, myxoid metastasis occurred with the partial spontaneous disappearance of the primary nonmyxoid malignant melanoma.

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 histologic and clinical variants of melanoma: Implications for therapy

Unusual histologic variants of melanoma may prove problematic to the histopathologist. Several of these variants are sufficiently rare that their biological behavior remains obscure. Because identification of some of these melanoma subtypes has specific implications for the therapeutic approach and some may mimic other forms of epithelial or mesenchymal neoplasia, their recognition is key to patient management.

Cutaneous melanoma with pseudomyxoid features

A 96-year-old man presented with a polypoid melanoma, which showed a prominent clear stroma, similar to that of myxoid melanoma, but stained negative for Alcian blue at pH 2.5 and for colloidal iron. It is not clear whether melanoma displaying pseudomyxoid features (pseudomyxoid melanoma) may represent a distinct histological variant of melanoma. However, it must be differentiated from true myxoid melanomas, in which Alcian blue-positive acid mucopolysaccharides are present. Urso C. Cutaneous melanoma with pseudomyxoid features.

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.

Myxoid clear cell sarcoma

Clear cell sarcoma is a rare soft-tissue tumor presenting typically in the extremities of young adults. It has been also known as malignant melanoma of the soft parts because of the presence of melanin and cytoplasmic melanosomes. However, clear cell sarcoma is, at present, usually considered as a unique lesion because the t(12;22)(q13;q12) translocation is present only in clear cell sarcoma. Myxoid malignant melanoma is now a well-recognized morphologic variant of malignant melanoma. However, a myxoid variant of clear cell sarcoma has not been well described yet. We report a case of myxoid clear cell sarcoma occurring on the heel in a 22-year-old man. The tumor was composed of nests and fascicles of oval to fusiform cells with clear to pale eosinophilic cytoplasm, often separated by fibrous septa. The tumor cells were reactive for S-100 protein, HMB-45, and MART-1. Variably sized cysts lined by one or several layers of tumor cells were observed. Alcian blue and mucicarmine stains demonstrated prominent mucin deposition in the tumor stroma and especially in the lumen of the cysts. Fluorescence in situ hybridization for the Ewing sarcoma gene showed rearrangement in nearly all of the neoplastic cells.

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.

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.

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.