Probability analyses of combining background concentrations with model-predicted concentrations.

UNLABELLED: In order to calculate total concentrations for comparison to ambient air quality standards, monitored background concentrations are often combined with model predicted concentrations. Models have low skill in predicting the locations or time series of observed concentrations. Further, adding fixed points on the probability distributions of monitored and predicted concentrations is very conservative and not mathematically correct. Simply adding the 99th percentile predicted to the 99th percentile background will not yield the 99th percentile of the combined distributions. Instead, an appropriate distribution can be created by calculating all possible pairwise combinations of the 1-hr daily maximum observed background and daily maximum predicted concentration, from which a 99th percentile total value can be obtained. This paper reviews some techniques commonly used for determining background concentrations and combining modeled and background concentrations. The paper proposes an approach to determine the joint probabilities of occurrence of modeled and background concentrations. The pairwise combinations approach yields a more realistic prediction of total concentrations than the US. Environmental Protection Agency's (EPA) guidance approach and agrees with the probabilistic form of the National Ambient Air Quality Standards. IMPLICATIONS: EPA's current approaches to determining background concentrations for compliance modeling purposes often lead to "double counting" of background concentrations and actual plume impacts and thus lead to overpredictions of total impacts. Further, the current Tier 1 approach of simply adding the top ends of the background and model predicted concentrations (e.g., adding the 99th percentiles of these distributions together) results in design value concentrations at probabilities in excess of the form of the National Ambient Air Quality Standards.

The risk of lymph node involvement in malignant cutaneous adnexal tumors.

Malignant cutaneous adnexal tumors (MCATs) are rare neoplasms that do not have a well-studied treatment algorithm. They are generally treated by excision alone. Given its successful application in other cutaneous malignancies, sentinel lymph node biopsy (SLNB) has been advocated by some for use in MCATs. A retrospective chart review was performed. Clinicopathological factors, recurrence patterns, and long-term follow-up were documented. Survival analysis was performed. Forty-eight subjects were identified. Mean age was 69 years with locations on the face (52%), including periocular sites (16%), extremities (25%), and all other sites (7%). Histologic distribution was sebaceous carcinoma (56%), porocarcinoma (17%), eccrine carcinoma (13%), adenocarcinoma (10%), and hidradenocarcinoma (4%). Mean follow-up was 3.9 years (range, 0 to 17 years). Nine subjects (18.8%) recurred locally, and recurrence was inversely associated with age (P = 0.04). Four (8.3%) demonstrated lymph node involvement, none without first developing local recurrence. Five-year disease-specific survival was 97 per cent (confidence interval, 81.4 to 99.6%). Despite being one of the largest reported analyses of MCATs, this study is limited by the small number of subjects. MCATs seemingly develop nodal recurrence only after demonstrating aggressive local biology. SLNB may best be applied selectively, possibly only in patients with local recurrence.

The General Surgeon's quandary: atypical lipomatous tumor vs lipoma, who needs a surgical oncologist?

BACKGROUND: Differentiating large lipomas from atypical lipomatous tumors (ALT) is challenging, and preoperative management guidelines are not well defined. The diagnostic ambiguity leads many surgeons to refer all patients with large lipomatous masses to an oncologic specialist, perhaps unnecessarily. STUDY DESIGN: In this retrospective cohort study of patients with nonretroperitoneal lipomatous tumors, preoperative characteristics discernible without invasive diagnostic procedures were evaluated for diagnostic predictive value. RESULTS: We identified 319 patients (256 with lipomas, 63 with ALTs) treated between 1994 and 2012. Patients with ALTs were older (60.5 vs 53.5 years, p < 0.0001), had larger tumors (16.0 vs 8.3 cm, p < 0.0001), had tumors more often located on an extremity (88.9% vs 60.5% torso, p < 0.0001), and more frequently had a history of previous operations at the same site, exclusive of excision leading to diagnosis and referral (20.6% vs 5.9%, p = 0.001). Local recurrence was observed in 2 patients with lipomas (0.8%) vs 14 with ALTs (22.6%, p < 0.0001). No patients with ALTs developed distant metastases or disease-specific mortality, with a median follow-up of 27.4 months (range 0 to 164.6 months). On multivariate analysis, age ≥ 55 years, tumor size ≥ 10 cm, extremity location, and history of previous resections were predictors for diagnosis of ALT (p < 0.05). CONCLUSIONS: Characteristics of lipomatous masses associated with a diagnosis of ALT include patient age ≥ 55 years, tumor size ≥ 10 cm, previous resection, and extremity location (vs torso). These easily identifiable traits may guide surgical management or referral to a specialist.

1 or 2 cm margins of excision for T2 melanomas: do they impact recurrence or survival?

BACKGROUND: NCCN guidelines recommend 1 or 2 cm margins for melanomas 1-2 mm (T2 melanomas) in depth; however, no head-to-head comparison has been performed. We hypothesized 1- or 2-cm margins would have similar local recurrence (LR) and overall survival (OS). METHODS: An institutional database was queried for patients with 1.0-2.0 mm melanomas treated from July 1995 to January 2011. All had wide excision and sentinel lymph node biopsy. Patients without documented surgical margins or follow-up were excluded. Clinicopathologic and recurrence data were reviewed. Univariate and multivariate analyses were performed. RESULTS: Of 2,118 patients, 1,225 met study criteria. Of these, 576 had complete data: 224 (38.9%) had 1 cm margins and 352 (61.1%), 2 cm margins. Median follow-up was 38 months. Mean age was 52.6 years (range 11.3-86.7). Mean thickness was 1.27 and 1.48 mm (1 and 2 cm, respectively, p<0.001) with ulceration more common in the 2 cm group (12.3 and 21.3%, respectively; p=0.009). LR was 3.6 and 0.9% in the 1 cm versus 2 cm group, respectively (p=0.044). OS was 29.1 months with 1 cm and 43.7 months in the 2 cm group. On multivariate analysis, only head and neck location and nodal status were associated with overall survival. CONCLUSIONS: In this series, 1 cm margins were associated with a small increase in LR that did not impact OS. This is concordant with the NCCN recommendations; however, a prospective, randomized trial would be optimal.

Analysis of regional recurrence after negative sentinel lymph node biopsy for head and neck melanoma.

BACKGROUND: The head and neck have a rich lymphatic drainage and complex anatomy, which complicate sentinel lymph node (SLN) biopsy for melanoma. The incidence of regional recurrence after a negative SLN biopsy has been shown to be higher than that at other sites. Compounding factors in this scenario were analyzed to determine their impact on both SLN status and survival. METHODS: A retrospective review of a prospective database of 315 patients who underwent SLN biopsy for head and neck melanoma from 1994 to 2009 was performed. A false-negative SLN biopsy was defined as a regional recurrence in a previously mapped nodal basin. RESULTS: In all, 267 patients (84.8%) were SLN negative (SLN-) and 48 patients (15.2%) were SLN positive (SLN+). The false-negative SLN biopsy occurred in 17 patients (6.4%). The mean follow-up was 37.6 months (3-152 months). The false-negative SLN and SLN+ patients were similar with respect to patient age and sex and primary melanoma tumor thickness and ulceration. The site of the primary melanoma and the lymphatic drainage patterns did not influence the false-negative biopsy rate. The mean survival was SLN- 119.3 months (95% confidence interval [CI], 106.1-132.5, p < .001), SLN+ 73.4 months (95% CI, 52.3-94.4), and the false-negative SLN 70.7 months (95% CI, 54.2-87.1). CONCLUSIONS: The risk of a false-negative SLN biopsy in head and neck melanoma is independent of primary site and lymphatic drainage pattern. Patients with head and neck melanoma who have a regional recurrence after a negative SLN biopsy do not have a worse survival than that of patients who are initially SLN positive.

Inguinopelvic lymphadenectomy following positive inguinal sentinel lymph node biopsy in melanoma: true frequency of synchronous pelvic metastases.

BACKGROUND: True frequency of synchronous pelvic metastases with positive inguinal sentinel lymph node (SLN) biopsy is unknown. Role of pelvic dissection in the SLN era is unclear. METHODS: From 1994 to 2004, 1 surgeon routinely performed nonselective, complete inguinopelvic lymphadenectomy after positive inguinal SLN biopsy. All cases were identified from a prospectively maintained database. Clinicopathologic features associated with pelvic disease were assessed. RESULTS: A total of 40 patients with positive inguinal SLN underwent, without additional selection, 42 complete inguinopelvic lymphadenectomies. Median age was 46.5 years (range 25-79 years); 79% had lower extremity primaries. Median Breslow depth was 2.3 mm (range 1.0-10.0 mm), Clark's IV/V 98%, ulceration 26%. Frequency of synchronous pelvic disease upon completion lymphadenectomy was 5 of 42 (11.9%). Patients with and without pelvic disease were similar in age, sex, Breslow depth, Clark's level, ulceration, and mitoses. All 5 cases with pelvic metastases had extremity primaries (4 distal, 1 proximal). Of the 5, 3 (60%) had ≥3 total involved inguinal nodes, compared with only 1 (2.7%) of the 37 cases without pelvic disease (P=.003). Ratio of positive to total number inguinal nodes retrieved was >0.20 in 80% of cases with pelvic disease and 8.6% of cases without (P=.002). Upon lymphoscintigraphy review, secondary pelvic drainage was present in 80% of cases with pelvic disease compared with 56% of cases without pelvic disease, though the trend was statistically insignificant (P=.63). CONCLUSIONS: In this cohort of unselected, SLN-positive patients with complete inguinopelvic lymphadenectomy, frequency of synchronous pelvic disease was 11.9%. Patients with ≥3 total involved inguinal nodes or inguinal node ratio >0.20 appear more likely to harbor pelvic disease.

Routine biopsy of Cloquet's node is of limited value in sentinel node positive melanoma patients.

BACKGROUND AND OBJECTIVES: Biopsy of Cloquet's node (CN) during groin dissection has been used to indicate need for pelvic dissection. With earlier detection of microscopic regional disease in the era of sentinel node biopsy (SNB), frequency of positive CN may be so low that routine biopsy is unwarranted. METHODS: Patients with positive groin SNB from 2000 to 2008 were identified from two centers. Cases where CN was identified at completion node dissection were selected. Lymphoscintigraphic, surgical, pathologic, and recurrence data were reviewed. RESULTS: CN was identified in 53 cases. Median age was 44.5 years (range 7-77); median Breslow depth, 1.98 mm (range 0.5-25.0); % Clark's level IV/V, 90%; and % ulceration, 41.5%. Fifty (94.3%) underwent groin dissection alone; three others underwent concomitant pelvic dissection. Two (3.8%) patients had positive CN; both had additional indications for pelvic dissection. Delayed pelvic recurrence rate was 2/53 (3.8%); both patients had negative CN. In the three patients treated with concurrent groin and pelvic dissection, CN reflected pelvic nodal status in two cases; the third had pelvic metastases despite negative CN. CONCLUSIONS: After positive SNB, disease involvement of CN is rare. Patients with positive biopsies of CN in the SNB era appear likely to have additional indications for pelvic dissection, minimizing utility of CN biopsy. Routine intraoperative sampling of CN may not be warranted during groin dissection for positive SNB.

Utility of lymph node assessment for atypical spitzoid melanocytic neoplasms.

BACKGROUND: Atypical spitzoid melanocytic neoplasms (ASMN) are cutaneous lesions of uncertain malignant potential, which can be difficult to distinguish from cutaneous melanoma. Sentinel lymph node (SLN) biopsy is a safe and useful prognostic tool for staging melanoma, but its role in staging ASMNs is not established nor is the significance of positive SLNs in these patients known. This study attempts to characterize the significance of nodal disease in ASMN. METHODS: Patients with ASMNs who presented to the melanoma service from 1992 to 2007 were identified from a prospective database. Histological review was performed by two dermatopathologists. Demographic, treatment, and outcome data were reviewed. RESULTS: A total of 58 patients with ASMNs were treated during the time analyzed; 31 (53%) underwent wide local excision and observation (WLE); 27 underwent wide excision and SLN biopsy. Median age was 24 (range, 6-60) years. Mean Breslow thickness was 2.9 (range, 0.5-10) mm. Median follow-up was 56 (range, 1-160) months. Ten of 58 (17%) patients had nodal metastasis. Four (13%) of 31 patients who underwent WLE developed nodal recurrences, and 6 of 27 (22%) patients had a positive SLN biopsy. Of patients with positive SLNs, none have recurred after undergoing completion lymphadenectomy. One patient presented with synchronous brain metastasis and inguinal lymphadenopathy and died of disease. CONCLUSIONS: Nodal status does not seem to convey the same prognosis that it does in standard melanoma. There may be a limited ability for progression within the nodal basin in patients with these lesions. This subset of patients would benefit from genetic data complementing histologic analysis.

Regional recurrence after negative sentinel lymph node biopsy for melanoma.

OBJECTIVE: Sentinel lymph node (SLN) biopsy has shown great utility in the management of melanoma. An analysis of regional recurrence in previously mapped negative SLN basins as the first site of relapse is performed. METHODS: A retrospective query of a prospective melanoma database from 1994 to 2006 identified 1287 patients who underwent successful SLN biopsy. One thousand sixty patients (82.4%) were SLN negative and 227 (17.6%) patients SLN positive. Clinical variables were examined for the impact on regional recurrence by multivariate analysis. RESULTS: Mean follow-up was 44.3 months (range 3-155 months). Thirty-five patients (3.3%) presented with false-negative (FN) SLN biopsy. Pathologic review of the SLNs harvested from these basins found 7 (20.0%) samples positive for metastatic melanoma. Multivariate analysis found head and neck site [hazard ratio 3.67; 95% confidence interval (CI), 1.77-7.60, P < 0.001] and tumor thickness (hazard ratio 1.16; 95% CI, 1.04-1.30, P = 0.01) to be predictive of FN SLN biopsy. The 5-year melanoma specific survival calculated from the date of the SLN biopsy was 57.6% (95%CI, 35.7-41.9) in the FN group, which was not statistically different than the SLN positive group 60.0% (95% CI, 29.6-40.1; P = 0.14). CONCLUSIONS: Head and neck tumor site and tumor thickness are predictors of a FN SLN biopsy. Mechanisms other than pathologic SLN sampling error may contribute to the failure of the SLN biopsy in some patients. Patients with regional recurrence after negative SLN biopsy have a similar 5-year survival compared with patients with positive SLNs.

Sentinel lymph node biopsy in the management of cutaneous head and neck melanoma.

Sentinel lymph node biopsy has revolutionized the surgical management of primary malignant melanoma. Most series on sentinel lymph node mapping have concentrated on extremity and truncal melanomas. The head and neck region has a rich and unpredictable lymphatic system. The use of sentinel lymph node mapping in the management of head and neck melanoma is evaluated. The authors conducted a retrospective review of patients treated for clinical stage I and stage II malignant melanoma of the head and neck with dynamic lymphoscintigraphy and gamma probe-guided sentinel lymph node biopsy. One hundred thirty-two patients (99 male patients and 33 female patients) were identified. The primary melanoma sites were the scalp (n = 54), ear (n = 14), face (n = 37), and neck (n = 27). Primary tumor staging was as follows: T1, 11; T2, 38; T3, 39; and T4, 44. Dynamic lymphoscintigraphy visualized sentinel lymph nodes in 128 patients (97 percent). In 71 cases (55 percent), a single draining nodal basin was identified, and in 57 cases there were multiple draining nodal basins (two basins, 55; three basins, two). Sentinel lymph nodes were successfully identified in 176 of 186 nodal basins (95 percent). Positive sentinel lymph nodes were identified in 22 patients (17.6 percent). Sentinel lymph node positivity by tumor staging was as follows: T2, 10.8 percent; T3, 19.4 percent; and T4, 26.8 percent. Completion lymphadenectomy revealed residual disease in seven patients (33.3 percent). Sentinel lymph node mapping for head and neck melanoma can be performed with results comparable to those of other anatomical sites.

Rapid immunohistochemistry of sentinel lymph nodes for metastatic melanoma.

Sentinel lymph node (SLN) biopsy is performed on patients with malignant melanoma (MM) to assess the need for selective complete lymphadenectomy. Melanoma metastasis to regional lymph nodes is an important prognostic indicator in patients with MM. This study assesses the sensitivity and specificity of rapid immunohistochemistry (RIHC) in intraoperative delineation of melanoma metastasis to SLN. RIHC for S-100 protein, HMB45, and a melanoma marker cocktail (melan A, HMB45, and tyrosinase) was performed on 71 SLNs obtained from 28 patients with MM. Frozen sections (6 micro thick) on plus slides were fixed for 2 to 3 minutes in cold acetone and then stored at -70 degrees C. The EnVision kit (Dako, Carpinteria, CA) for rapid immunohistochemistry (RIHC) on frozen tissue sections was used, and the staining technique took 19 minutes. Together with preparation of the frozen sections and fixation in acetone, immunostained slides were available in approximately 25 minutes. Of the 71 SNLs examined, 7 showed melanoma metastasis in permanent sections. RIHC of frozen sections detected metastatic melanoma in 6 SLNs, with a sensitivity of 86% for HMB45 and 71% for S-100 protein and the melanoma cocktail and a specificity of 97% for HMB45 and 100% for S-100 and the melanoma cocktail. We conclude that RIHC for HMB45, S-100 protein, and the melanoma cocktail may help detect melanoma metastasis in SLN intraoperatively, leading to total lymph node dissection and obviating the need for 2 surgical procedures. Section folds and background stain can make interpretation difficult. Intraoperative time constraints require a more rapid technique. A recent consensus group has discouraged frozen-section examination of SLN.

The amount of metastatic melanoma in a sentinel lymph node: does it have prognostic significance?

BACKGROUND: The amount of metastatic disease in the sentinel lymph node (SLN) is examined as a prognostic factor in malignant melanoma. METHODS: SLN mapping was performed on 592 patients with stage I and II malignant melanoma from March 1, 1994, through December 31, 1999. One hundred four patients were found to have 134 sentinel SLNs containing metastatic melanoma. The slides were reviewed, and the size of the metastatic melanoma in each SLN was measured. The size of the metastatic deposit was defined as macrometastasis (>2 mm), micrometastasis (< or =2 mm), a cluster of cells (10-30 grouped cells) in the subcapsular space or interfollicular zone, or isolated melanoma cells (1 to > or =20 individual cells) in subcapsular sinuses. RESULTS: The number of metastases in each SLN was isolated melanoma cells, n = 5 (3.7%); cluster of cells, n = 35 (26.1%); < or =2 mm, n = 45 (33.6%); and >2 mm, n = 49 (36.7%). Seventy-nine patients (76%) had a single positive SLN. The size of the largest nodal metastasis was used to stratify patients with multiple positive SLNs. The overall 3-year survival for patients with SLN micrometastases was 90%, versus 58% for patients with SLN macrometastases (P =.004). CONCLUSIONS: The amount of metastatic melanoma in an SLN is an independent predictor of survival. Patients with SLN metastatic deposits >2 mm in diameter have significantly decreased survival.

Sentinel lymph node mapping for thick (>or=4-mm) melanoma: should we be doing it?

BACKGROUND: Thick (>or=4-mm) primary melanomas are believed to be associated with a high incidence of occult distant metastases. The use of sentinel lymph node (SLN) mapping and biopsy in the treatment lesions has been questioned. METHODS: A retrospective review of a computerized database identified 114 patients who underwent successful SLN mapping and biopsy from January 1, 1994, to December 31, 1999. Records were reviewed for clinicopathologic features of the patients and their tumors. Survival curves were constructed from Kaplan-Meier estimates and analyzed with log-rank tests and Cox proportional hazards modeling. RESULTS: There were 75 men and 39 women with a mean age of 57 years (range, 24-85 years). The primary tumor sites were head and neck (n = 29; 25.4%), trunk (n = 44; 38.6%), and extremities (n = 41; 36%). Tumor thickness ranged from 4 to 17 mm (median, 5.2 mm; mean, 6.3 mm). Ulceration was present in 40 (35.1%) tumors. Thirty-seven patients (32.5%) had a positive SLN biopsy, and 18 of these patients (48.6%) had a single tumor-positive lymph node after dissection. The mean follow-up was 37.8 months. The overall 3-year survival for SLN-negative patients was 82%, versus 57% for SLN-positive patients (P =.006). Lymph node status and tumor ulceration were independent predictors of overall survival in multivariate Cox regression analysis. CONCLUSIONS: The pathologic status of the SLN in patients with thick melanomas is a strong independent prognostic factor for survival, and SLN mapping should be routinely performed.

Local recurrence after skin-sparing mastectomy: tumor biology or surgical conservatism?

BACKGROUND: Long-term follow-up of the use of skin-sparing mastectomy (SSM) in the treatment of breast cancer is presented to determine the impact of local recurrence (LR) on survival. METHODS: A total of 539 patients were treated for 565 cases of breast cancer by SSM and immediate breast reconstruction from January 1, 1989 to December 31, 1998. The American Joint Committee on Cancer pathological staging was stage 0 175 (31%), stage I 135 (23.9%), stage II 173 (30.6%), stage III 54 (9.6%), stage IV 8 (1.4%), and recurrent 20 (3.5%). The mean follow-up was 65.4 months (range, 23.7-86.3 months). Five patients were lost to follow-up. RESULTS: Thirty-one patients developed a LR during the follow-up including five who received adjuvant radiation. The distribution of LR stratified by cancer stage was stage 0 1, stage I 5, stage II 17, stage III 6, and recurrent 2. The overall LR was 5.5%. Twenty-four patients (77.4%) developed a systemic relapse and 7 (22.6%) patients remained free of recurrent disease at a mean follow-up of 78.1 months. The cancer stage of those remaining disease free was stage 0 1 (100%), stage I 4 (80%), and stage II 2 (11.8%). CONCLUSIONS: LR of breast cancer after SSM is not always associated with systemic relapse.

Acral lentiginous melanoma mimicking benign disease: the Emory experience.

BACKGROUND: Plantar and subungual melanoma exhibits a higher misdiagnosis rate relative to other anatomic sites. Misdiagnosis and delay in diagnosis are statistically associated with poorer patient outcome. Awareness of atypical presentations of acral melanoma may, thus, be important to decrease misdiagnosis rates and improve patient outcome. METHODS: We conducted a retrospective case review of plantar or lower-extremity subungual melanoma performed at Winship Cancer Center, a tertiary care, referral center affiliated with Emory University, between 1985 and 2001. RESULTS: A total of 53 cases of plantar or lower-extremity subungual melanoma were identified. Of 53 cases with a final diagnosis of melanoma, 18 were initially misdiagnosed. Misdiagnoses included wart, callous, fungal disorder, foreign body, crusty lesion, sweat gland condition, blister, nonhealing wound, mole, keratoacanthoma, subungual hematoma, onychomycosis, ingrown toenail, and defective/infected toenail. Of the 18 misdiagnosed cases, 9 were clinically amelanotic. CONCLUSION: Awareness that amelanotic variants of acral melanoma may assume the morphology of benign hyperkeratotic dermatoses may increase the rate of correct diagnosis and improve patient outcome.

The use of skin sparing mastectomy in the treatment of breast cancer: The Emory experience.

INTRODUCTION: Long-term follow-up of the use of skin sparing mastectomy (SSM) in the treatment of breast cancer is presented to determine the impact of local recurrence (LR) on survival. METHODS: 565 cases of breast cancer were treated by SSM and IBR from 1/1/1989-12/31/1998. The AJCC pathological staging was Stage 0 175 (31%), Stage I 135 (23.9%), Stage II 173 (30.6%), Stage III 54 (9.6%), Stage IV 8 (1.4%), recurrent 20 (3.5%). Forty-one patients received postoperative adjuvant radiation therapy. RESULTS: Thirty-one patients developed a LR during the follow-up including five who received adjuvant radiation. The distribution of LR stratified by cancer stage was Stage 0 1 (3.2%), Stage I 5 (16.1%), Stage II 17 (54.8%), Stage III 6 (19.4%), and recurrent 2 (6.5%). The overall LR was 5.5%. Isolated LRs were treated with surgical resection and radiation therapy if not previously administered. Twenty-four patients (77.4%) developed a systemic relapse and 7 (22.6%) patients remained free of recurrent disease at a mean follow-up of 78.1 months. The cancer stage of those remaining disease free was Stage 0 1, Stage I 4, and Stage II 2. CONCLUSIONS: LR of breast cancer after SSM is not always associated with systemic relapse.

The definition of the sentinel lymph node in melanoma based on radioactive counts.

BACKGROUND: There is no consensus on the definition of a hot, nonblue sentinel lymph node (SLN), despite the widespread use of radiocolloid in SLN mapping. METHODS: A retrospective review of 592 patients with malignant melanoma who underwent SLN mapping was performed. Ex vivo SLN counts and nodal bed counts were obtained by using a gamma probe. The size of each metastatic deposit in an SLN was defined as macrometastases (>2 mm), micrometastases (< or =2 mm), a cluster of cells, or isolated melanoma cells. RESULTS: A total of 1175 SLNs (SLN(-), n = 1041; SLN(+), n = 134) were evaluated. The mean SLN count/bed counts were SLN(-), 322 +/- 980 and SLN(+), 450 +/- 910 (not significant [NS]) (>2 mm, 270 +/- 792 [NS]; < or =2 mm, 446 +/- 693 [NS]; isolated melanoma cells/cluster of cells, 677 +/- 1189 [P =.036]). Overall, 16 (1.4%) of the SLNs collected had an overall ratio of < or =2. This included two positive SLNs (1.5%), both of which contained macrometastatic disease. Forty-seven positive nodal basins had at least one negative SLN. The hottest SLNs in these basins were negative for metastatic disease in nine cases (19.1%). In one basin (2.1%), the positive SLN count was <10% of the hottest lymph node count. CONCLUSIONS: Removal of lymph nodes until the bed count is 10% of the hottest lymph node will remove 98% of positive SLNs. Lymph node tumor burden influences radioactive counts.