Spindle Cell Melanoma Research Articles

CD10, p63 and CD99 expression in the differential diagnosis of atypical fibroxanthoma, spindle cell squamous cell carcinoma and desmoplastic melanoma

Atypical fibroxanthoma (AFX) is a pleomorphic spindle cell lesion of the skin; it is considered in the differential diagnosis with spindle cell malignant melanoma (MM) and sarcomatoid carcinoma/spindle cell squamous cell carcinoma (SCC). An optimum approach has yet to fully emerge with respect to the immunohistochemical discrimination of these lesions. Departmental archives from 1978 onwards were searched for clinicopathologically confirmed cases of AFX, MM and SCC. Immunostains for CD10, CD99 and p63 were performed in each case. Scored staining results were analyzed using Fisher's Exact Test. Twenty-seven of 31 cases of AFX were positive for CD10, as compared with 3 of 22 SCCs and 0 of 20 MMs. CD10 positivity was preferentially associated with the diagnosis of AFX (p < 0.001). p63 reactivity was observed in 15/22 cases of SCCs, 5/31 AFXs and 1/20 MMs. CD99 reactivity was observed in 3/31 cases of AFX, 2/22 SCCs and 3/20 MMs. CD10 positivity is relatively specific in this context for the diagnosis of AFX. Its utility is enhanced when only strong, diffuse membranocytoplasmic staining is considered as a positive result. In contrast to prior reports, p63 was not found to be highly sensitive for SCC. Similarly, CD99 showed no preferential staining of any single diagnostic group of lesions.

Primary cutaneous myxoid spindle cell squamous cell carcinoma: a clinicopathologic study and review of the literature

Mucocutaneous squamous cell carcinoma (SCC) may rarely exhibit intracellular mucin production. Extracellular mucin production is an even rarer finding in SCC that is not well documented in the literature. Here, we report six cases of primary cutaneous and mucocutaneous SCC with prominent extracellular stromal mucin deposition and an epithelial spindle cell component. We propose the term 'yxoid spindle cell SCC' (MSC SCC) to describe the histologic characteristics of these six cases. We also propose a set of histologic and immunohistochemical findings for distinguishing MSC SCC from primary cutaneous and metastatic spindle cell neoplasms including other sarcomatoid carcinomas, myxoid sarcomas and the spindle cell variant of atypical fibroxanthoma (AFX). The criteria can also help discern MSC SCC from spindle cell melanomas, which may rarely show a prominent myxoid stroma. Given the small numbers of cases reported to date, the presence of prominent myxoid stroma in primary cutaneous spindle cell SCC has unknown prognostic significance at this time.

Cutaneous Clear Cell Sarcoma: A Clinicopathologic, Immunohistochemical, and Molecular Analysis of 12 Cases Emphasizing its Distinction from Dermal Melanoma

Clear cell sarcoma (CCS) of tendons and aponeuroses/malignant melanoma (MM) of soft parts is a rare tumor and in the majority of cases presents a characteristic reciprocal translocation t(12;22)(q13;q12) that results in fusion of the EWS and ATF1 genes. Although the melanocytic differentiation of CCS is indisputable, its precise lineage remains unclear. Typically, the slowly growing tumor affects the extremities of adolescents or young adults, especially around the ankle and foot. CCS is classically regarded as a deep soft tissue tumor associated with tendons or aponeuroses. This traditional view is put into perspective by the description of primary CCS of the gastrointestinal tract that may have a variant fusion gene EWSR1-CREB1. We describe 12 cases of cutaneous CCS and discuss the differential diagnoses. These 12 cases share an identical immunohistochemical profile with MM and thus can easily be confused with a dermal variant of spindle cell MM or metastasis of MM. The patients' ages ranged from 6 to 74 years (median: 25 y), and there was a female predominance (10 females, 2 males). Most tumors (n = 9) were located on the extremities, 2 tumors arose on the back, and 1 on the abdomen. The mean tumor size was 0.97 cm (range, 0.4 to 1.7 cm). Six cases showed invasion of the subcutis, the other 6 cases were entirely dermal. Tumor necrosis was evident in 2 cases, melanin pigment in 2 cases, and ulceration in 1 tumor. All cases showed uniform nests and fascicles of pale spindled or slightly epitheloid cells with finely granular eosinophilic or clear cytoplasm. There was fair pleomorphism with plump spindled nuclei and significantly prominent nucleoli. Multinucleated wreath-like tumor giant cells were observed in two-thirds of cases, but were usually present only focally. The dense cellular aggregates were encased by delicate fibrous septa. The stroma showed a sclerotic reticulated pattern. Partly, the nests of spindle cells bordered the epidermis, prima vista mimicking junctional nests of melanocytes. The specific translocation pattern was confirmed in all cases by fluorescence in situ hybridization. Local recurrences and metastases developed in 2 and 3 patients, respectively, and 1 patient died of the disease.

Fine‐needle aspiration cytology in a case of metastatic spindle cell melanoma in liver

Fine‐needle aspiration cytology in a case of metastatic spindle cell melanoma in liver

Claudin-5 protein is a new differential marker for histopathological differential diagnosis of canine hemangiosarcoma.

Claudin-5 protein is an endothel-specific claudin, present in tight junctions. To evaluate its usefulness as a differential diagnostic marker of canine hemangiosarcomas, the expression of claudin-5 molecule was studied in different canine tumours of vascular origin. Ninety two canine neoplastic tissue samples obtained from necropsies and biopsy specimens were routinely processed and stained immunhistochemically for claudin-5. The neoplastic endothelial cells of canine hemangiosarcomas, hemangiomas, and lymphangiomas showed a strong membrane immunoreactivity for claudin-5, but the other investigated canine malignant and benign tumours, including fibrosarcomas, myxo-, leiomyo-, cardiac rhabdomyo-, neurofibro-, synovial-, osteo-, and chondrosarcomas, spindle cell melanomas, hemangio-pericytomas, benign fibroblast proliferations, and leiomyomas were negative for this endothelial marker. In these non-vascular canine tumours intense immunostaining was detected in the endothelial cells of the incorporated intratumoural vessels and neovasculature. The canine splenic hematomas induced by hemangiosarcomas were distinguished from splenic hematomas induced by non-neoplastic lesions by the means of claudin-5 protein. In hemangiosarcomas the percentage of positive neoplastic endothelial cells was higher, and stronger when using the claudin-5 molecule compared to CD31 and vWf. The results show that claudin-5 molecule can be used as a new differential marker, and could also be of a diagnostic value in the differential diagnosis of canine hemangiosarcomas from sarcomas of other origin with hemorrhages or increased vascularization. Claudin-5 could help to reveal neoplastic proliferation of endothelial cells causing splenic hematomas and differentiate these tumours from non-vascular neoplastic splenic lesion. The immunohistochemical detection of the claudin-5 protein had a higher sensitivity than CD31, and vWf antigen in case of canine hemangiosarcomas.

Utility of p63 in the differential diagnosis of atypical fibroxanthoma and spindle cell squamous cell carcinoma

Atypical fibroxanthoma (AFX), spindle cell squamous cell carcinoma (SCSCC) and spindle cell melanoma are the primary entities in the differential diagnosis of a cytologically atypical spindle cell tumor arising on sun-damaged skin. AFX is generally regarded as a diagnosis of exclusion in this context: in the absence of S100 or keratin reactivity, a diagnosis of AFX is favored. However, keratin reactivity may be focal or even absent in SCSCC, and although numerous positive markers of AFX have been proposed, none has shown sufficient sensitivity and specificity for routine diagnostic use. We evaluated 20 AFX and 10 SCSCC with a panel of cytokeratins and p63 to assess the utility of the latter antibody in this differential diagnosis. All 10 SCSCC showed strong expression of p63, whereas all 20 AFX were p63 negative. Two additional cases (excluded from the study) were negative for keratins and S100 on initial shave biopsies, resulting in a favored diagnosis of AFX, but p63 stains performed retrospectively were positive. However, review of the excision specimens in both cases revealed deep subcutaneous extension, excluding AFX. p63 reactivity argues against the diagnosis of AFX and is therefore a useful addition to the standard immunohistochemical panel for cutaneous spindle cell neoplasms.

New techniques in dermatopathology that help to diagnose and prognosticate melanoma

Routine light microscopy supplemented with immunohistochemistry in cases of metastatic or spindle cell melanoma are standards of care for the diagnosis and staging of melanoma. Not all melanocytic tumors can be confidently classified as melanoma or benign nevus by histology, however. In addition, tumor thickness and ulceration, the current American Joint Classification on Cancer prognosticators for primary cutaneous (stages I and II) melanoma used in clinical practice, do not perfectly predict an individual's clinical course. Recent advances in molecular techniques and bioinformatics mandate testing and use of novel methods for the detection, diagnosis, and classification of melanocytic tumors that can accurately predict tumor behavior and help in selecting the most optimal and individualized therapy.

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.

An unusual penile spindle cell malignancy

AbstractPrimary non-epithelial malignancies of the penis are rare. We report a patient with an unusual presentation of an unexpected spindle cell malignancy at this site. A 35- year-old man presented with a mass in the shaft of the penis with inguinal lymphadenopathy. A malignant spindle cell neoplasm was seen involving the corpora, consistent with leiomyosarcoma. Immunohistochemically, the tumour was positive for S100, HMB-45 and negative for SMA. A final diagnosis of amelanotic spindle cell melanoma was made. This case is being presented to reiterate the importance of including melanoma in the differential diagnosis of spindle cell sarcomas at uncommon sites.

Immunohistochemical Distinction of Cutaneous Spindle Cell Carcinoma

Cutaneous spindle cell squamous carcinoma is an uncommon variant of squamous cell carcinoma in which keratinocytes infiltrate the dermis as single cells with elongated nuclei rather than as cohesive nests or islands, and signs of keratinization of conventional squamous cell carcinoma are insubstantial or nonexistent. Spindle cell carcinoma must be distinguished from spindle cell/desmoplastic melanoma, cutaneous leiomyosarcoma, atypical fibroxanthoma (AFX), and scar. In instances when there is no definitive evidence of squamous differentiation, immunohistochemical studies may confer diagnostic discrimination. Twenty-four cases consisting of 12 spindle cell squamous cell carcinomas, 3 AFXs, 3 leiomyosarcomas, 3 desmoplastic melanomas, and 3 scars were evaluated with a battery of immunohistochemical stains, with the specificity and sensitivity of each marker calculated. The immunohistochemical battery consisted of S-100, desmin, CD68, and smooth muscle actin and cytokeratins P KER (keratins predominantly of molecular weight 56 and 69 kd) and low-molecular weight keratin (CAM 5.2), AE1/AE3, p63, and 34 beta E12 (CK903). Spindle cell squamous carcinomas were negative for S-100, CD68, smooth muscle actin, and desmin with the exception of 2 cases with weak staining for smooth muscle actin. 34 beta E12 provided positive results for each spindle cell squamous carcinoma. The other cytokeratin stains were less sensitive for spindle cell squamous carcinoma than 34 beta E12. The final immunohistochemical results were as follows: 34 beta E12 (12/12, 100%), p63 (10/12, 80%), AE1/AE3 (8/12, 67%), low-molecular weight keratin (7/12, 58%), and P KER (4/12, 33%). The 3 AFXs were positive for CD68 and negative for all other stains, whereas the 3 leiomyosarcomas stained positively for desmin and smooth muscle actin and negatively for all other stains. The 3 melanomas stained positively for S-100 and negatively for all other immunohistochemistry. The scars were negative for all stains. In conclusion, our study of 34 beta E12 proved most promising in distinguishing spindle cell squamous carcinoma from the histologic mimickers, AFX, spindle cell melanoma, scar, and leiomyosarcoma.

Desmoplastic Malignant Melanoma: A Clinicopathologic Analysis of 113 Cases

Desmoplastic melanoma (DM) is a rare variant of spindle cell melanoma, which usually develops in sun-damaged skin of elderly patients. Often the lesion is nonpigmented and frequently mistaken for a nonmelanocytic proliferation, which delays diagnosis and treatment and therefore worsens the prognosis. The spindle shape of neoplastic melanocytes, the prominent desmoplasia, and the frequent neurotropism of neoplastic melanocytes are its most characteristic histopathological features. We have studied the clinicopathologic features of 113 cases of DM. The mean age of the patients was 71.1 years; 48% of the patients were males and 52% were females. The neoplasm was located on the head in 72% of the cases. Malignant melanoma was the initial clinical diagnosis in only 27% of the cases. Histopathologically, all lesions appeared as poorly demarcated neoplasms that involved the entire dermis and often extended into the subcutaneous tissue. The neoplasms were composed of ill-defined fascicles of spindle cells. Desmoplasia was defined as the presence of spindle cells associated with a fibrotic stroma. Fifty-one cases (45%) were classified as "pure DM" when the lesion was entirely desmoplastic, and 62 cases (55%) were considered as "combined DM" when a recognizable desmoplastic component was seen in an otherwise conventional malignant melanoma. In 81% of the cases, an atypical intraepidermal melanocytic component (in situ malignant melanoma) was identified, whereas in the remaining 19% of the cases the intraepidermal component was lacking. Seventy-one percent of the cases were histologically amelanotic, 23% showed a small amount of pigment, and only 6% were heavily pigmented. Neural involvement was identified in 40/113 cases (35%), predominantly in the thickest tumors. Lymphoid nodules, found in 42/113 cases (37%), were significantly more frequent in pure DM than in combined DM (53% vs 24%). The null hypothesis of homogeneity of the "pure" and "combined" subgroups should be rejected (P < 0.002). Solar elastosis, with variable intensity, was seen in 82% of the cases. Mean Breslow thickness was 4.1 mm (4.6/3.7 mm, in the pure/combined subgroups, respectively), median was 4.0 mm (4.0/3.0 mm); Breslow thickness ranged from 0.3 to 11.0 mm, with half of the cases thicker than 4 mm. Only 4% of the cases showed Clark level below IV. The predominant neoplastic cells consisted of spindle-shaped melanocytes in 85% of the cases, whereas the remaining 15% of the cases demonstrated round neoplastic cells forming the main mass of the neoplasm. The mitotic rate of the neoplastic cells was low in 72% of the cases, 23% had an intermediate mitotic rate, and 5% showed a high mitotic rate. On follow-up, 55/113 patients (49%) (with an average of 55 months) demonstrated persistence of the disease. About 4% had local recurrences, 2% of lymph node invasion, 9% systemic metastases, and 12% died from the disease (2 cases of pure DM and 5 cases of combined DM). Although a better prognosis has been postulated for DM when compared with conventional cutaneous malignant melanomas of the same thickness, in most cases, a DM is diagnosed only in established long-standing and thick melanomas. Therefore, dermatologists and dermatopathologists should be more aware of this clinicopathologic variant of cutaneous malignant melanoma.

Correlation of histological findings from a large ciliochoroidal melanoma with CT perfusion and 3T MRI dynamic enhancement studies

The initial use of a 64-slice computed tomography (CT) scanner for obtaining quantitative perfusion data from a large ciliochoroidal melanoma, and correlation with 3T magnetic resonance imaging (MRI) dynamic enhancement and tumor histology. The CT perfusion scan was performed using 80 kVp, 250 mA and 1-sec rotation time for 40 sec. The analysis was performed using commercial perfusion analysis software with a prototype 3-dimensional motion correction tool. Dynamic contrast-enhanced 3-Tesla MRI measured the kinetics of enhancement to estimate the vascular permeability. The time-dependent enhancement patterns were obtained using the average signal intensity using Functool analysis software. The involved globe was enucleated and microscopic evaluation of the tumor was performed. The perfusion parameters blood flow, blood volume and permeability surface area product in the affected eye determined by CT perfusion analysis were 118 ml/100 ml/min, 11.3 ml/100 ml and 48 ml/100 ml/min. Dynamic MRI enhancement showed maximal intensity increase of 111%. The neoplasm was a ciliochoroidal spindle cell melanoma which was mitotically active (13 mitoses/40 hpf). Vascular loops and arcades were present throughout the tumor. The patient developed metastases within 9 months of presentation. Quantitative CT perfusion analysis of ocular tumors is feasible with motion correction software.

Diagnostic Implications of Podoplanin Expression in Peripheral Nerve Sheath Neoplasms

By using the D2-40 antibody, we have observed podoplanin expression in Schwann cells and perineurial cells. Podoplanin expression has not been well characterized in peripheral nerve sheath tumors. Because neoplasms of neural crest lineage, including peripheral nerve sheath and melanocytic neoplasms, may share histologic and immunohistochemical characteristics, we evaluated podoplanin and S-100 expression in these lesions to determine the usefulness of podoplanin as a diagnostic marker. Diffuse podoplanin and S-100 expression was observed in 16 (76%) of 21 classical schwannomas, 6 (100%) of 6 cellular schwannomas, and 3 (75%) of 4 epithelioid malignant peripheral nerve sheath tumors (EMPNSTs). Podoplanin was expressed in 3 (7%) of 43 neurofibromas, 16 (21%) of 75 spindle cell MPNSTs (SMPNSTs), and 1 (10%) of 10 spindle cell melanomas but was absent in conventional melanoma. Only rare neurofibromas and SMPNSTs showed strong coexpression of podoplanin and S-100. These results suggest diffuse podoplanin expression or coexpression of podoplanin and S-100 is limited to schwannoma and EMPNST and may be useful in the evaluation of these neoplasms.

KBA.62: a useful marker for primary and metastatic melanomas

We previously described a novel antimelanoma antibody, designated KBA.62. However, review of the literature showed that only a few studies have reported on this antibody. We report our experience in the diagnosis of melanoma using KBA.62 and its value in both primary and metastatic conditions. In addition to conventional melanomas, we included desmoplastic and spindle cell melanomas, whose diagnosis can be challenging. We also focus on identification of malignant cells in sentinel lymph node biopsies using KBA.62, by comparison with anti-S-100 protein and HMB-45 antibodies, because discrepancies in sensitivity and specificity of melanoma markers have given rise to numerous studies aiming to determine the best panel for the evaluation of sentinel lymph node from patients with melanoma. Overall, KBA.62 was positive in 93% of primary and metastatic melanomas. Interestingly, the 12 cases of desmoplastic and spindle cell melanomas had strongly positive results. In addition, the results of our study performed on a series of 215 sentinel lymph nodes showed that the sensitivity of anti-S-100 protein and KBA.62 antibodies in detecting occult metastasis was similar. Moreover, KBA.62 identified 6 patients (3%) who had confirmed sentinel lymph node metastasis but were negative for HMB-45. The resolution was higher with KBA.62 than that observed with anti-S-100 protein antibody, as the nonmelanocytic positive cells for KBA.62 in lymph nodes were only represented by endothelial cells, which therefore constituted an intrinsic positive control. We conclude that KBA.62 antibody is a useful additional marker for melanoma, specifically in desmoplastic/spindle cell cases and in the context of micrometastasis in sentinel lymph node.

Desmoplastic Neurotropic Melanoma in a Patient With Trigeminal Neuralgia

A 51-year-old man presented with a hard subcutaneous nodule adhering to the underlying bone structures of the left eyelid in 2004. Histopathology showed a desmoplastic neurotropic melanoma (DNM) with perineural invasion. Patient presented with a first recurrence in October 2005, which was treated by surgery. In August 2006 he presented with trigeminal neuralgia of the left face in the area innervated by the first and second branches of the trigeminal nerve. A PET scan clearly shows the tumoral hypermetabolism of the subcutaneous recurrence of the neurotropic melanoma with invasion of the second or maxillary branch that follows the nerve up to the trigeminal ganglion, which was detected despite the physiological high uptake in the temporal lobe. MRI confirms the invasion and a second PET and MRI 6 months later done to evaluate resectability showed progressive disease. DNM is a rare subtype of spindle cell melanoma. It corresponds to dermal proliferation of desmoplastic cells of neural differentiation. Unlike other melanomas, however, survival for DNM may be better compared with other forms of melanoma. This rare case report presents PET imaging involving cranial nerve invasion by this uncommon melanoma subtype.

Immunohistochemical characteristics of melanoma

Melanoma has a wide spectrum of histologic features which mimic epithelial, hematologic, mesenchymal, and neural tumors. Immunohistochemistry has been the primary tool to distinguish melanomas from these other tumors; it has also been studied for use as an adjunct to distinguish benign and malignant melanocytic tumors and to elucidate prognosis. Furthermore, there has been extensive effort to find a suitable marker to differentiate spindle cell and desmoplastic melanoma from other tumors. We have reviewed the literature investigating melanocytic differentiation markers, proliferation markers, immunomodulatory markers, signaling molecules, and nerve growth factors and receptors. Despite the proliferation of immunohistochemical markers, S-100 remains the most sensitive marker for melanocytic lesions, while markers such as HMB-45, MART-1/Melan-A, tyrosinase, and MITF demonstrate relatively good specificity but not as good sensitivity as S-100. No marker has proven useful in distinguishing spindle cell and desmoplastic melanomas from other tumors. Ki67 remains the most useful adjunct in distinguishing benign from malignant melanocytic tumors. None of the markers reviewed has been shown conclusively to have prognostic value for melanocytic neoplasms.

Report of a metaplastic carcinoma of the breast with multi-directional differentiation: an adenoid cystic carcinoma, a spindle cell carcinoma and melanoma

Metaplastic carcinoma of the breast is a heterogeneous neoplasia, generally composed of both epithelial and mesenchymal components. We report an unusual case of mammary metaplastic carcinoma in a 51-year-old female patient. Needle core biopsy from the tumour mass showed malignant epithelial and sarcomatous features. The resection specimen revealed a multi-directional tumour differentiation consisting predominantly of: firstly, a poorly differentiated basaloid epithelial cell type, consistent with an adenoid cystic carcinoma; secondly, areas of a spindle cell carcinoma; and, thirdly, areas with a melanocytic differentiation. This is the first report on a metaplastic carcinoma of the breast presenting as an admixture of an adenoid cystic carcinoma and melanoma.

Diagnostic challenges of metastatic spindle cell melanoma on fine-needle aspiration specimens

Spindle cell melanoma is a morphologic variant of melanoma that can be difficult to diagnose on specimens obtained via fine-needle aspiration (FNA). Published cytology studies concerning this entity were based for the most part on small series. In the current study, a large series of metastatic spindle cell melanoma is described and the diagnostic pitfalls present in FNA samples addressed. The authors retrospectively reviewed the cytologic features of 81 metastatic spindle cell melanoma specimens obtained from 67 patients. Corresponding primary tumors or metastatic tumors taken elsewhere from the same patient were also evaluated. The cytologic smears were mostly cellular and comprised of predominantly spindle tumor cells that frequently formed cohesive fascicles or whorls intermingled with scattered epithelioid tumor cells. The classic cytologic characteristics of conventional melanoma (predominantly dyshesive cellular distribution, cytoplasmic melanin pigments, intranuclear pseudoinclusions, macronucleoli, and binucleation or multinucleation) were noted infrequently or, if present, were more readily found in coexisting epithelioid cells. Remarkably, 9% of the cases failed to demonstrate any of the above classic characteristics. In addition, spindle cells demonstrated a wide range of cytologic atypia, from deceptively bland cells resembling reactive fibroblasts to those indistinguishable from pleomorphic high-grade sarcomatous neoplasms. When the morphologic features were compared with those of the primary tumor or metastatic melanoma taken elsewhere from the same patient, cell type discrepancy was found in 20% of the cases in that the previous counterparts demonstrated the epithelioid cell type. Spindle cells also tended to lose immunoexpression of melanoma markers. Spindle cell melanoma infrequently demonstrates the diagnostic cytologic features and immunoreactivity of conventional melanoma. Varying degrees of cytologic atypia and possible cell type differences from the primary counterpart or metastatic melanoma occurring elsewhere are additional sources of diagnostic challenges, especially in the metastatic setting. Familiarity with cytologic features, combined with clinical and immunoperoxidase findings, is required to avoid misinterpretation.

S100 A6 immunohistochemical staining for spindle cell and desmoplastic melanomas

S100 A6 immunohistochemical staining for spindle cell and desmoplastic melanomas

WT1 as a complementary marker of malignant melanoma: an immunohistochemical study of whole sections

To test the usefulness of WT1 as a diagnostic aid in melanoma diagnosis and prognostication. Benign naevi, Spitz naevi, dysplastic naevi and melanoma in situ, primary epithelioid, spindle cell and desmoplastic melanoma, and metastatic melanoma biopsy specimens were collected. Primary melanoma cases were grouped using the 2003 Tumour Node Metastasis classification. Cases were examined using haematoxylin and eosin and WT1-stained sections. The presence and pattern of WT1 expression were recorded. Benign naevi were uniformly negative with WT1. The majority of Spitz naevi expressed WT1 (83%). The dysplastic naevi/in situ group showed expression of WT1 in 35% of cases. The majority of primary epithelioid melanoma cases showed WT1 expression (88%). The prevalence of expression by each T category was similar, with T1 = 90%, T2 = 75%, T3 = 95% and T4 = 90%. All spindle cell and desmoplastic melanoma cases showed WT1 expression (100%). Ninety per cent of metastatic melanoma cases expressed WT1. WT1 is a useful ancillary diagnostic tool in routine melanoma diagnosis. WT1 expression in primary melanoma is unrelated to tumour depth. Its usefulness is limited by the fact that most Spitz naevi express WT1, up to one-third of dysplastic naevi can express WT1 and not all melanomas demonstrate its expression.