Cutaneous Richter syndrome: report of 3 cases from one institution.

BACKGROUND: Richter syndrome (RS) is large-cell transformation of chronic lymphocytic leukemia (CLL). It commonly involves lymph nodes and bone marrow, but may rarely manifest in skin. Certain triggering factors, such as Epstein-Barr virus infection and p53 overexpression, have been implicated in the pathogenesis of RS. Here, we present 3 cases of cutaneous RS from our institution with a follow-up period of up to 8 years. OBJECTIVE: We present a series of cutaneous RS from a single institution with the longest follow-up period (up to 8 years) to date. METHODS: Clinical characteristics were collected and histopathological findings of skin biopsy specimens were analyzed. RESULTS: All 3 patients had prior CLL and later developed cutaneous RS lesions. The mean age at the diagnosis of cutaneous RS was 67 years old. The time intervals between CLL and cutaneous RS were 3 to 8 years. Skin biopsy specimens demonstrated dermal nodular or perivascular infiltrates of large B cells, showing similar immunophenotypes to the lesional cells in the original CLL. Overexpression of p53 and positive stain for Epstein-Barr virus--encoded small RNA was found in one patient. One patient remained alive 8 years after the diagnosis whereas the other two died of the disease at 5 years and 3 weeks, respectively, after the onset of cutaneous RS. LIMITATIONS: Three patients with RS were followed up for up to 8 years. CONCLUSIONS: Our findings suggested that, in contrast to extracutaneous RS, cutaneous RS generally has a less aggressive course with longer survival unless other worse prognostic factors are present.

Rapid clinical change in lesions of atypical cutaneous lymphoproliferative disorder in an HIV patient: a case report and review of the literature.

BACKGROUND: HIV associated atypical cutaneous lymphoproliferative disorder (ACLD) is a rare condition characterized by a pruritic, often generalized, eruption of patches and plaques or erythroderma clinically simulating mycosis fungoides (MF) or Sézary syndrome. A polyclonal CD8+ T-cell infiltrate on biopsy can help differentiate ACLD from MF or Sézary syndrome, but the clinical and histopathologic appearance must also be considered. Accurate diagnosis is imperative because HAART therapy has been reported to improve this condition in some patients. OBSERVATION: We report a case of HIV associated ACLD, with an atypical presentation, initially consisting of diffuse papules, some with a dusky targetoid center. Two weeks after starting antiviral therapy the papules flattened, evolving to xerotic, hyperpigmented macules. CONCLUSION: The working-theory of a reactive etiology for this condition might explain the evolution in appearance following initiation of HAART. The presence of papules with a dusky targetoid center suggests that this condition should be considered in the differential diagnosis with syphilis or atypical erythema multiforme in HIV patients.

Two cases of syringotropic cutaneous T-cell lymphoma and review of the literature.

Syringotropic cutaneous T-cell lymphoma (CTCL) is a rare form of CTCL characterized histologically by infiltrates of atypical lymphocytes located primarily in and around hyperplastic eccrine glands and ducts. Currently, syringotropic CTCL is classified as a histopathologic variant of folliculotropic mycosis fungoides (MF); however, the relationship between these two entities remains tenuous. We report two additional cases of syringotropic CTCL and review the differences between these two subtypes of MF with regard to epidemiology, clinical features, prognosis, and treatment. Based on these data, we conclude that syringotropic CTCL should be classified as a distinct variant of MF separate from folliculotropic MF.

Comparison of CD23 staining patterns in Merkel cell carcinoma and non-cutaneous small cell carcinoma.

BACKGROUND: During our daily practice, we observed that cluster designation 23 (CD23) (clone BU38) labels Merkel cells in normal skin. In this study, we examined the expression of CD23 in Merkel cell carcinoma (MCC) and assessed its usefulness in distinguishing MCC from non-cutaneous small cell carcinoma (SMCC). METHODS: Immunohistochemical staining of CD23 was performed on a total of 33 MCCs, 22 SMCCs and 5 carcinoid tumors. RESULTS: CD23 reactivity was present in 32 of 33 (97%) MCCs, 18 of 22 (82%) SMCCs and 5 of 5 (100%) carcinoid tumors. In MCC, 19 cases (59%) showed a predominance of perinuclear dot-like staining similar to cytokeratin 20, 3 (9%) showed mostly cytoplasmic staining and 10 (31%) displayed a combination of perinuclear dot-like and cytoplasmic staining. In contrast, all CD23-positive SMCCs and carcinoid tumors showed a diffuse cytoplasmic staining. There was a significant difference in the CD23 staining patterns between MCC and SMCC (p < 0.0001). CONCLUSION: CD23 is expressed in the majority of MCC, SMCC and carcinoid tumor irrespective of clinical outcome. The distinct punctate CD23 staining for MCC may be helpful in differentiating it from SMCC. To our knowledge, this is the first study to show the expression of CD23 in neuroendocrine tumors.

Expression of gamma-H2AX in melanocytic lesions.

gamma-H2AX is a marker of activated DNA damage and is overexpressed in many malignancies and their precursor lesions. Previous studies have demonstrated the expression of gamma-H2AX in melanoma and dysplastic nevus, but its diagnostic and prognostic utility in a full range of melanocytic lesions has not been fully studied. In the current study, we investigated gamma-H2AX expression in a total of 162 melanocytic lesions. We found that gamma-H2AX was observed at higher levels (percentage and intensity of staining) in melanoma in situ (12/13), primary cutaneous melanoma (32/33; with the exception of desmoplastic melanoma), and metastatic melanoma (58/62), which was statistically different from that in benign nevus (7/9), dysplastic nevus (6/10), and Spitz nevus (5/9) considered together (P < .0001). Of note, desmoplastic melanoma (20/26) demonstrated weak or negative gamma-H2AX staining. The expression of gamma-H2AX did not show significant correlation with many melanoma prognostic factors, including Breslow depth, mitotic rate, and sentinel lymph node status. Except for desmoplastic melanoma, no difference in gamma-H2AX levels was observed among various melanoma subtypes. The overexpression of gamma-H2AX in melanoma as opposed to nevus indicates its possible role in melanomagenesis. Based on the overlap in subsets of nevi and melanomas, the potential clinical utility of this antibody remains uncertain until further studies have been carried out in a larger cohort of melanocytic lesions, including borderline cases.

The expression of MUM1 in cutaneous T-cell lymphoproliferative disorders.

MUM1 is a member of the interferon regulatory factor family of transcription factors. It is normally expressed in plasma cells, late B cells, and activated T cells, and has been described in several B-cell malignancies. Although its expression has been reported in some T-cell neoplasms, the full range and character of expression have not been explored. We studied 58 cases of T-cell lymphoproliferative lesions, including systemic and cutaneous anaplastic large cell lymphoma, lymphomatoid papulosis (LyP), mycosis fungoides (MF), MF with large cell transformation, and Sézary syndrome (SS). Nearly all cutaneous (5/5) and systemic anaplastic large cell lymphomas (4/5) were positive for MUM1, mainly in the large cell population. Similarly, 12 of 16 types A and C LyP showed MUM1 reactivity in greater than 50% of the large cells. Focal MUM1 staining was seen in 3 type B LyP, mostly in reactive lymphoid cells. All 9 MF with large cell transformation expressed MUM1 in large cells, where it paralleled CD30 expression. In comparison, most MF (11/12) were MUM1 negative. Interestingly, all SS cases (8/8) were MUM1 positive, 3 of which demonstrated diffuse staining. There was a significant difference in MUM1 expression between MF and SS groups as well as between MF and large cell transformation of MF groups (P < .001 for both). In summary, MUM1 is not helpful in separating different types of CD30-positive lymphoproliferative disorders. Potentially, MUM1 could serve as an adjunct marker for SS and/or large cell transformation of MF.

Nephrogenic systemic fibrosis: a report of 29 cases.

OBJECTIVE: The purpose of this study was to determine the incidence of nephrogenic systemic fibrosis and its relation to renal failure and the administration of gadolinium-based contrast material at an academic medical center. MATERIALS AND METHODS: A dermatopathology database was searched to identify patients in whom nephrogenic systemic fibrosis was diagnosed. The medical records of these patients were reviewed. Renal function concurrent with any administration of gadolinium-based contrast material was assessed, as was patient outcome. A database of patients undergoing long-term dialysis was reviewed separately to determine how many had received gadolinium and the frequency of nephrogenic systemic fibrosis among these patients. RESULTS: Twenty-nine patients were found to have had nephrogenic systemic fibrosis between November 15, 1999, and December 31, 2006. It was known that gadolinium-based contrast material had been administered to 25 of these patients before diagnosis. All 29 patients had compromised renal function (27 had chronic renal failure, and two had acute renal failure). Determination of the temporal relation between gadolinium-based contrast administration and symptom onset often was difficult. Only eight patients had severe morbidity. Nephrogenic systemic fibrosis developed in 12 (2.9%) of 414 patients undergoing long-term dialysis who received gadolinium-based contrast material. CONCLUSION: We confirm the strong association between nephrogenic systemic fibrosis and gadolinium-based contrast administration. Although the use of high doses of gadolinium and the occurrence of chronic renal failure have been implicated in other reports, several of our patients received standard doses of gadolinium, and two had transient acute renal failure before diagnosis. Most patients had mild or moderate symptoms. Nephrogenic systemic fibrosis developed in 2.9% of patients undergoing long-term dialysis who received gadolinium-based contrast material but in none of the long-term dialysis patients who did not receive gadolinium-based contrast material.

The expression of CD23 in cutaneous non-lymphoid neoplasms.

BACKGROUND: Cluster designation 23 (CD23) is generally used as a lymphoid marker. Its utility in cutaneous epithelial tumors has never been studied. In our routine practice, we observed that CD23 reacted strongly with eccrine and apocrine secretory coils. METHODS: Immunohistochemical staining of CD23 was performed in a total of 131 cases of apocrine, eccrine, follicular and other cutaneous non-lymphoid tumors. RESULTS: CD23 expression was detected in all benign apocrine tumors and in half of benign eccrine tumors, particularly those derived from secretory coils. CD23 staining was seen in 42% (8/19) of microcystic adnexal carcinoma (MAC), while no staining was observed in tumor cells of desmoplastic trichoepithelioma, morpheaform basal cell carcinoma and syringoma. All mammary and extramammary Paget's disease were labeled with CD23. In comparison, pagetoid Bowen's disease, melanoma in situ and sebaceous carcinoma exhibited negative staining. In addition, CD23 reacted diffusely with cutaneous mucinous eccrine carcinoma in a manner similar to breast or colonic adenocarcinoma. CONCLUSION: CD23 appears to be a reliable immunohistochemical marker of the eccrine/apocrine secretory coil and helpful in identifying sweat gland tumors of such origin. It is of ancillary value in differentiating MAC from its mimicker. CD23 is a useful addition to the diagnostic immunohistochemical panels for Paget's disease.

Expression of polycomb group protein EZH2 in nevi and melanoma.

BACKGROUND: Enhancer of zeste homolog 2 (EZH2), a polycomb group protein that regulates the cell cycle, has recently been implicated in the progression of several human cancers. We sought to determine the pattern of EZH2 expression in benign and malignant melanocytic tumors to see if EZH2 might play a role in melanoma pathogenesis and progression. METHODS: We identified and reviewed 11 compound nevi, 13 dysplastic nevi, 13 Spitz nevi, 9 in situ melanomas, 10 non-metastatic invasive melanomas and 19 melanomas metastatic to lymph nodes from the University of Michigan pathology archives. Sections immunostained with anti-EZH2 antibody were scored independently and blindly for staining intensity on a scale of 1-4 by three dermatopathologists. Results were analyzed and compared statistically. RESULTS: We observed an incremental increase in EZH2 expression from benign nevi to melanoma: scores of 1.18 and 1.08 for ordinary and dysplastic nevi, 1.7 and 1.78 for Spitz nevi and in situ melanoma, and 1.9 and 3.0 for invasive and metastatic melanoma, respectively. EZH2 expression for metastatic melanoma was significantly higher compared with invasive and in situ melanoma and benign nevi (p < or = 0.01). CONCLUSIONS: EZH2 protein levels increase incrementally from benign nevi to melanoma, which suggests that EZH2 may play a role in the pathogenesis and progression of melanoma.

Telomerase expression in sebaceous lesions of the skin.

BACKGROUND: Recent studies have demonstrated telomerase expression in ophthalmologic sebaceous carcinoma and have suggested possible diagnostic utility in distinguishing these neoplasms from sebaceous adenomas. The aim of this study was to evaluate telomerase expression via human telomerase reverse transcriptase (hTERT) immunohistochemical staining in a spectrum of sebaceous lesions of the skin. METHODS: Paraffin-embedded sections from sebaceous hyperplasia (11), nevus sebaceus (22), sebaceous adenoma (19), sebaceoma (11), and sebaceous carcinoma (14) were evaluated for intensity (0 to 3+) and pattern of anti-hTERT staining. RESULTS: Strong (2 to 3+) hTERT staining was observed in nucleoli of germinative cells and immature sebocytes in all sebaceous lesions, whereas mature sebocytes were negative. The distribution pattern paralleled features seen by routine haematoxylin and eosin-stained sections. CONCLUSIONS: All hyperplastic and neoplastic sebaceous skin lesions expressed hTERT in this immunohistochemical study. The pattern of staining was predictive of the histologic pattern of the process but does not significantly add to our diagnostic armamentarium of sebaceous lesions.

What is a sentinel node? Re-evaluating the 10% rule for sentinel lymph node biopsy in melanoma.

INTRODUCTION: Many surgeons use the "10% rule" to define whether a lymph node is a sentinel node (SLN) when staging malignant melanoma. However, this increases the number of SLN removed and the time and cost of the procedure. We examined the impact of raising this threshold on the accuracy of the procedure. METHODS: We reviewed the records of 561 patients with melanoma (624 basins) who underwent SLN with technetium Tc99 labeled sulfur colloid using a definition of a SLN as 10% of that of the node with the highest counts per minute (CPM). RESULTS: Of the 624 basins, 154 (25%) were positive for metastases. An average of 1.9 nodes per basin were removed (range 1-6). Metastases were found in the hottest node in 137 cases (89% of positive basins, 97% of basins overall). Increasing the threshold above 10% decreased the number of nodes excised and the costs involved, but incrementally raised the number of false negative cases above baseline (a 4% increase for a "20% rule," 5% for a "30% rule," 6% for a "40% rule," and 7% for a "50% rule"). Taking only the hottest node would raise the false negative rate by 11%. CONCLUSIONS: Although using thresholds higher than 10% for the definition of a SLN will minimize the extent of surgery and decrease the costs associated with the procedure, it will compromise the accuracy of the procedure and is not recommended.

Significance of multiple lymphatic basin drainage in truncal melanoma patients undergoing sentinel lymph node biopsy.

BACKGROUND: Truncal melanoma involving metastases to multiple lymph node basins has a much worse prognosis than tumor involvement of a single lymph node basin. Recent results also suggest that, independently of the status of lymph node involvement, patients with multiple lymphatic basin drainage (MLBD) on lymphoscintigraphy have an increased risk of lymph node metastasis and a worse prognosis than those with a single lymphatic drainage basin. Because published reports have conflicting results, the authors compared their experience at the University of Michigan Comprehensive Cancer Center with recently published findings. METHODS: The authors searched a prospectively maintained melanoma database at the University of Michigan for patients with primary truncal melanoma who underwent lymphoscintigraphy and sentinel lymph node biopsy between 1997 and 2004. The association of MLBD with the clinical and pathologic characteristics collected and the presence of regional metastases was tested by using contingency tables and the chi(2) test statistic and by using the Fisher's exact test statistic when cell frequencies were small. The product-limit method of Kaplan and Meier was used to estimate disease-free and overall survival probabilities. RESULTS: Of 423 patients with primary truncal melanoma who underwent sentinel lymph node biopsy, 123 (29%) had a positive result, and 98 patients (23.2%) had MLBD. Patients with tumors located in the middle of the trunk and tumor ulceration were more likely to have MLBD (P < .0001 and P = .045, respectively). Patients with a single lymphatic drainage basin and MLBD had a similar risk of lymph node metastasis and similar disease-free and overall survival. CONCLUSIONS: Patients with truncal melanomas tend to have MLBD when the tumor is located in the middle of the trunk or when ulceration is present. In our experience, drainage to multiple lymphatic basins was not an independent risk factor for sentinel lymph node metastasis and has no independent prognostic significance.

Anti-oncogenic role of the endoplasmic reticulum differentially activated by mutations in the MAPK pathway.

Dysfunction of the endoplasmic reticulum (ER) has been reported in a variety of human pathologies, including cancer. However, the contribution of the ER to the early stages of normal cell transformation is largely unknown. Using primary human melanocytes and biopsies of human naevi (moles), we show that the extent of ER stress induced by cellular oncogenes may define the mechanism of activation of premature senescence. Specifically, we found that oncogenic forms of HRAS (HRAS(G12V)) but not its downstream target BRAF (BRAF(V600E)), engaged a rapid cell-cycle arrest that was associated with massive vacuolization and expansion of the ER. However, neither p53, p16(INK4a) nor classical senescence markers--such as foci of heterochromatin or DNA damage--were able to account for the specific response of melanocytes to HRAS(G12V). Instead, HRAS(G12V)-driven senescence was mediated by the ER-associated unfolded protein response (UPR). The impact of HRAS on the UPR was selective, as it was poorly induced by activated NRAS (more frequently mutated in melanoma than HRAS). These results argue against premature senescence as a converging mechanism of response to activating oncogenes and support a direct role of the ER as a gatekeeper of tumour control.

BRAF and NRAS mutations in spitzoid melanocytic lesions.

BRAF mutations are common events in a variety of melanocytic nevi and primary cutaneous melanomas. We have previously found BRAF mutations in 82% of nevi, consisting of congenital, common acquired and dysplastic types, and 33% of primary cutaneous melanomas other than the spitzoid type, similar to other published reports. A small number of studies have evaluated Spitz nevi and have failed to detect any lesions possessing a BRAF mutation. Only one study included categories of atypical Spitz nevus and borderline lesions suspected to be spitzoid melanomas, along with classic Spitz nevi and spitzoid melanomas. We examined a spectrum of spitzoid lesions that included 48 Spitz nevi, some with atypical features, seven atypical (borderline) Spitz tumors, and 13 spitzoid melanomas. BRAF mutations were detected in 12 of 68 spitzoid lesions, of which two were spitzoid melanomas and 10 were Spitz nevi. Five of the 10 Spitz nevi with BRAF mutations were altered by more than usual cytologic atypia and/or architectural atypia overlapping with dysplastic nevi, or irritation/inflammation; one desmoplastic Spitz nevus had a BRAF mutation. These results indicate that a small subset of Spitz nevi, some with atypical histologic features, possess BRAF mutations. Therefore, the BRAF mutational status does not separate all Spitz nevi from spitzoid melanomas and non-Spitz types of melanocytic proliferations, contrary to previous reports.

hTERT expression in melanocytic lesions: an immunohistochemical study on paraffin-embedded tissue.

BACKGROUND: Telomerase plays a role in the immortalization of cells and carcinogenesis. Previous studies have yielded conflicting results on whether human telomerase RNA (hTER) expression differs in nevi, atypical nevi and melanomas using polymerase chain reaction-based telomeric repeat amplification protocol or in situ hybridization assays. The aim of this study was to evaluate human telomerase reverse transcriptase (hTERT) staining in melanocytic lesions on paraffin-embedded tissues. METHODS: Paraffin-embedded sections from 12 acquired nevi, seven dysplastic nevi, 11 Spitz nevi, eight primary invasive melanomas, and three metastatic melanomas were studied for staining intensity (0-3+) and percentage of labeled cells with anti-hTERT. RESULTS: hTERT staining was observed in most cells (>75%), in all but three lesions, and was of greater intensity in the nucleus, especially the nucleolus, compared with the cytoplasm. Spitz nevi tended to have weaker hTERT staining (mean = 1.7) compared with acquired nevi (mean = 2.2), dysplastic nevi (mean = 2.4), primary melanomas (mean = 2.4), or metastatic melanomas (mean = 3). CONCLUSIONS: Although telomerase activity was weaker in Spitz nevi, there was overlap with other nevi and primary invasive melanomas in our small series. Thus, hTERT expression does not appear to be a reliable adjunct to the histological diagnosis of primary melanocytic lesions.

Wide excision without radiation for desmoplastic melanoma.

BACKGROUND: Adjuvant radiation has been proposed for the treatment of patients with desmoplastic melanoma, who reportedly have local recurrence rates as high as 40-60%. The authors investigated local recurrence rates at a tertiary referral center to determine the success of wide excision alone for patients with desmoplastic melanoma. METHODS: A review of a prospectively maintained melanoma clinical data base identified 65 patients between March 1997 and March 2004 with pure cutaneous desmoplastic melanoma. Complete surgical, histopathologic, and staging information was collected along with data on outcome, including local, regional, and distant recurrence and survival. RESULTS: Similar to previous reports, patients with desmoplastic melanoma had a male-to-female ratio of 2 to 1, a mean age of 65.0 years (range, 31-92 yrs), and the majority of their tumors (55%) were located on the head and neck. The mean Breslow depth at diagnosis was 4.21 mm, with 38% of tumors thicker than 4.0 mm. All patients in this series underwent wide excision without radiation therapy. Surgical margins < or = 2 cm were obtained for all trunk and extremity lesions and for 63% of head and neck lesions that measured > 1 mm in depth (63%). Margins of 1-2 cm were obtained for the remaining patients. Among 49 patients who had a minimum of 2 years of follow-up (mean, 3.7 yrs), the local recurrence rate was 4% (2 of 49 patients). Seventy-eight percent of the patients studied remained alive with no evidence of disease. CONCLUSIONS: Local recurrence rates in the current series were considerably lower than the historically reported rates. This finding suggests that, for patients with desmoplastic melanoma, wide local excision with careful attention to appropriate margins produces excellent local control rates without the need for adjuvant radiation.

Cluster designation 5 staining of normal and non-lymphoid neoplastic skin.

BACKGROUND: Immunohistochemical staining for cluster designation 5 (CD5) has been found to label a variety of non-lymphoid tumors. METHODS: A variety of eccrine, apocrine, follicular, epithelial, and pagetoid lesions were selected and stained with an anti-CD5 monoclonal antibody (Novocastra Labs, Newcastle upon Tyne, UK, clone 4C7) by immunohistochemistry. The intensity of positive cytoplasmic staining was graded semiquantitatively (1+ weak staining, 2+ strong staining). Additionally, the percentage of positive lesional cells was placed in one of four categories: >75%, 25-75%, 1-25%, and <1%. RESULTS: Within normal skin, CD5 labeled lymphocytes, apocrine glands, deep dermal eccrine glands, and smooth muscle (weak). The majority of benign and malignant apocrine lesions demonstrated strong focal (36%, n=11)-to-diffuse (64%, n=16) staining. In contrast, labeling of benign eccrine tumors was more focal, tending to localize around ducts (79%, n=19). Microcystic adnexal carcinoma demonstrated focal staining of deeper ductal structures (71%, n=7), whereas desmoplastic trichoepithelioma and basal cell carcinoma showed only rare positive cells. All cases of mammary (n=7) and extramammary (n=8) Paget's disease labeled diffusely for CD5. Pagetoid Bowen's disease (n=6), intraepidermal sebaceous carcinoma (n=3), nor melanoma in situ (n=6) showed any CD5 staining. CONCLUSIONS: Immunohistochemical staining for CD5 is extremely useful in the differential diagnosis of pagetoid epidermal lesions and will mark mammary and extramammary Paget's disease, but not pagetoid Bowen's disease, melanoma in situ, or sebaceous carcinoma.

Choroidal and skin metastases from papillary thyroid cancer: case and a review of the literature.

A patient with widely metastatic papillary thyroid cancer who had been previously treated with (131)I and external beam radiation presented with purple nodular lesions on his face and scalp. On biopsy, the nodules were papillary carcinoma with cells that stained for thyroglobulin. Subsequently he developed decreased left eye visual acuity, and fundoscopy revealed lesions typical of choroidal metastases. Dermal and choroidal metastases of papillary thyroid carcinoma are both rare. However, the significance of these clinical manifestations may be overlooked and ignored unless the diagnosis is considered. New skin nodules or visual acuity decline in a patient with papillary thyroid cancer may represent manifestations of distant metastatic disease and should prompt thorough evaluation with dermatological examination and fundoscopy. Choroidal and skin metastases have almost always occurred in patients with advanced disease, but initial presentation with these lesions is possible, and in such instances a thorough search for additional sites of metastatic disease is recommended. Occasionally such metastases may respond to (131)I therapy or external beam radiation.

Standard immunostains for melanoma in sentinel lymph node specimens: which ones are most useful?

BACKGROUND: Sentinel lymph node (SLN) biopsy in melanoma is an increasingly used procedure. Pathologic evaluation of SLNs using immunohistochemistry improves diagnostic accuracy, yet no universally accepted standard protocol for pathologic processing of SLNs exists. OBJECTIVE: The primary purpose of this study was to evaluate our experience with the sensitivity of the immunostains S-100, HMB-45, and Melan-A for SLN biopsy. METHODS: Ninety-nine positive SLNs from 72 patients were retrospectively reviewed for the presence of microscopic metastatic melanoma on hematoxylin and eosin (H&E), S-100, HMB-45, and Melan-A stained sections and sensitivities of each immunohistochemical stain were determined. RESULTS: The sensitivities of S-100, HMB-45, and Melan-A were 97%, 75%, and 96% respectively. CONCLUSION: Given the lower sensitivity of HMB-45, our practice for evaluation of SLN biopsy specimens was modified using combinations of H&E, S-100, and Melan-A without HMB-45. If the H&E sections are negative or equivocal for metastatic melanoma, immunohistochemistry staining with S-100 protein and Melan-A is performed. New and improved protocols will undoubtedly be forthcoming as the field advances.