BosniakⅡ~Ⅳ级肾囊性占位临床与病理学特点分析简

目的 探讨Bosniak Ⅱ-Ⅳ级肾囊性占位临床与病理学特点。方法 回顾性分析上海交通大学医学院附属仁济医院从2008年1月至2012年12月CT诊断为囊性肾脏占位（BosniakⅡ、ⅡF、Ⅲ、Ⅳ）的170例患者的病例资料,其中Ⅱ级囊肿73例,ⅡF级囊肿34例、Ⅲ级囊肿38例、Ⅳ级囊肿25例。男105例,女65例;年龄20-85岁,平均（56±14.2）岁;病灶位于左侧87例,右侧66例,双侧17例。80例接受手术治疗的患者中,Ⅱ级囊肿18例,ⅡF级囊肿8例,Ⅲ级囊肿30例,Ⅳ级囊肿24例;行腹腔镜肾囊肿去顶减压术25例,腹腔镜肾部分切除术15例,腹腔镜根治性肾切除术7例,开放肾癌根治术6例,开放肾部分切除术27例。其余90例进行了影像学的随访。分析不同分型囊性肾脏占位的良恶性比例、病理学特点、随访结果。结果 手术病例中Ⅱ级囊肿恶性病例为1例（5.6%）,ⅡF级1例（12.5%）,Ⅲ级16例（53.3%）,Ⅳ级21例（87.5%）,组间比较有明显统计学差异（P＜001）。术后病理结果：恶性肿瘤共39例（透明细胞癌31例,乳头状癌8例）,Fuhrman分级均为Ⅰ级。良性病例共41例（单纯囊肿26例,囊肿伴出血3例,囊肿伴感染5例,囊性肾瘤4例,错构瘤3例）。术后患者随访时间为6-65月,平均随访25月,恶性病例均无发生局部复发或远处转移。影像学随访病例中BosniakⅡ级为55例,ⅡF级26例, Ⅲ级为8例,Ⅳ级为1例,随访时间为6-64月,其中1例Ⅱ级（1.8%）进展至ⅡF级,其余病例均未进展。结论 Ⅱ、ⅡF级囊肿恶性率较低、进展缓慢建议定期随访,而Ⅲ、Ⅳ级恶性率较高应积极手术处理。但由于囊性肾癌组织学分级往往较低,其术后复发、进展及远处转移率较低,保肾手术是首选的治疗方案。     

Magnetic resonance imaging as an adjunct diagnostic tool in computed tomography defined Bosniak IIF–III renal cysts: a multicenter study

Introduction

CT imaging is the standard examination for renal cystic lesions and defines the Bosniak category, which dictates further management. Given that Bosniak II/IIF/III renal cystic lesions can potentially harbor renal cell carcinoma (RCC), additional diagnostic modalities may be required in management decision making.

Aim

To determine the value of additional magnetic resonance imaging in CT-defined Bosniak IIF–III renal cystic lesions.

Materials and methods

This a multicenter retrospective study of 46 consecutive patients, diagnosed with cystic renal lesions between 2009 and 2016. The inclusion criteria were: (1) cystic renal lesion classified as Bosniak IIF–III on CT, (2) a subsequent MRI examination, and (3) documented outcome via surgery for cystic renal mass or follow-up.

Results

46 patients (35 males, 11 females) were included. The mean size of the cystic lesion was 3.92 cm (0.7–10 cm). According to the CT findings, Bosniak IIF and III were found in 12 (26.1%) and 34 (73.9%) cases. Reclassification of Bosniak category was done after MRI examination in 31 cases (67.4%). An upgrade rate of 58.7% (27 cases) to a higher category was made, while the downgrade rate to a lower category was achieved in 4 cases (8.7%). As a result, significant therapeutic management change was made in 12/31 patients (38.7%), of whom 8 underwent subsequent surgery.

Conclusion

MRI study may reduce the use of Bosniak IIF category (in comparison with CT), which has a direct impact on therapeutic management (surgery vs. surveillance) in a significant proportion of patients.

     

Comparación entre tomografía computarizada y resonancia magnética en la evaluación de quistes renales complejos empleando la clasificación de Bosniak

Introduction and objectivesThe Bosniak classification of cystic renal lesions was first published in 1986 based on computed tomography (CT). In the present study, we aimed to investigate the effect of magnetic resonance imaging (MRI) on Bosniak category compared with CT, and to determine how this effect changed the treatment modality in the evaluation of complex renal cysts.Material and methodsData of 144 patients were collected retrospectively. After exclusion criteria, 102 cystic renal lesions with a Bosniak category of at least IIF on CT or MRI between 2013 and 2016 were evaluated by 2 abdominal radiologists. The demographic data, Bosniak category, interobserver agreement, and pathologic data of patients who underwent surgery were recorded.ResultsThe coherence between MRI and CT was 75.5%. The Bosniak classification of 17 patients was upgraded with MRI, and the treatment modality changed in 10 patients, and they underwent surgery. The Bosniak category was downgraded from III to IIF in 6 patients out of 8 whose Bosniak category was downgraded with MRI and the treatment modality changed. Surgery was performed in one patient out of these 6 patients, and the pathology was reported as benign. Progression was detected in the follow-up at month 18 of 1 patient out of 5, and surgery was performed. The pathology was reported as renal cell carcinoma. The pathology result was reported as RCC in 35 (68.6%) patients out of 51 who underwent surgery. Progression was detected in 7 patients out of 51 who were followed up (13.7%), and the pathology results were reported as RCC. The majority of the malignant tumors were low stage and grade.ConclusionsMRI may be successfully used in the evaluation of renal cystic lesions. In particular, the challenging Bosniak IIF and all Bosniak III lesions must be evaluated using MRI before making the decision for surgery. The upgrading of Bosniak category with MRI is more possible compared with CT due to its high-contrast resolution, therefore further studies are required to identify whether it was the cause of overtreatment of Bosniak III lesions.     

Progression,interobserver agreement,and malignancy rate in complex renal cysts (≥Bosniak category IIF)

ObjectiveThe objective of this study was to assess interobserver agreement, clinicopathologic correlation, and radiologic follow-up progression of complex cystic renal masses.Patients and methodsThe medical records of 143 patients with 154 complex cystic renal masses were retrieved. Primary outcomes were interobserver agreement between the radiologists, and malignancy rates following surgical extirpation with or without follow-up in Bosniak IIF, III, and IV categories. Secondary outcomes were correlation between histology and degree of enhancement on contrast-enhanced computed tomography scans and survival analysis of patients with or without surgical intervention using the Kaplan-Meier analysis.ResultsThe overall malignancy rate in patients who had surgery was 74.5% (29/39). Of 27 confirmed renal cell carcinoma on final histology, 9 were papillary renal cell carcinoma (incidence 33.3%). Assessment of interobserver agreement yielded a weighted kappa statistic value of 0.69 (95% confidence interval 0.56–0.82, P<0.0001). Radiologic progression rate of Bosniak IIF cysts over median follow-up of 18.5 months was 13% (10/78). There was no statistically significant difference between progression rate and regression rate of IIF cysts (13.8% vs. 11.5%) over the period of 24 months of follow-up. Most of the progression in complex cystic renal masses was seen in the first 2 years of follow-up. The malignancy rate on radiologic progression was 87.5% (8/9) and 75% (6/8) in Bosniak IIF and III cystic masses, respectively. The malignancy rate in Bosniak III cyst was 50% (4/8) without a period of initial observation or follow-up.ConclusionsA good degree of agreement exists between radiologists in classifying complex renal masses. Malignancy rate is considerably high in Bosniak IIF when they exhibit radiologic progression on systematic follow-up.     

An evaluation of Bosniak's radiological classification of cystic renal masses

OBJECTIVE: To determine the clinical usefulness of Bosniak's classification of cystic renal masses, the differentiation of which remains difficult despite significant advances in diagnostic imaging. PATIENTS AND METHODS: The computed tomography (CT) findings of all histopathologically examined cystic renal masses diagnosed at our institution were analysed retrospectively; 35 patients with cystic renal masses were treated between 1986 and 1998. Tissues surgically removed were examined pathologically and the final diagnosis compared with the preoperative CT category of Bosniak's classification. RESULTS: The histopathological examined showed cystic renal cell carcinoma in 21 patients, a benign renal cyst in 12, haemangiosarcoma in one and transitional cell carcinoma in one. Most of the 35 masses (26, 74%) were found incidentally during evaluation for an unrelated disease or a routine health check. All 11 masses of Bosniak category I were benign and one category II mass was malignant. All 10 masses of category III and 12 of category IV were malignant. CONCLUSIONS: Bosniak's classification is useful for differentiating category I, III and IV cystic renal masses. There were too few samples to allow meaningful conclusions to be drawn for category II renal masses. It is critical to differentiate between complicated cysts of category II and III because of the major implications for prognosis and clinical management.     

Multilocular cystic renal cell carcinoma: clinicopathological features and preoperative prediction using multiphase computed tomography

Study Type – Diagnostic (exploratory cohort) Level of Evidence 2b What’s known on the subject? and What does the study add? Multilocular cystic renal cell carcinoma (MCRCC), defined according to the 2004 WHO classification, has good prognosis, which is not affected adversely by large tumour size or advanced stage. Thus nephron‐sparing surgery is proposed when MCRCC is suspected by preoperative radiologic criteria. The present study confirms the low malignant potential of MCRCC. Additionally, the results of the present study provide a simple, useful criteria using a Bosniak classification and Hounsfield unit on multiphase computed tomography images to differentiate MCRCC from other cystic RCC.

OBJECTIVE

? To analyse the clinicopathological and radiological features of multilocular cystic renal cell carcinoma (MCRCC) and to determine the preoperative factors differentiating MCRCC from other cystic RCC (CRCC).

PATIENTS AND METHODS

? The medical records of 53 patients with complex cystic renal masses evaluated by multiphase computed tomography (CT), surgically removed and confirmed as sporadic RCC were reviewed. ? Of these 53 patients, 23 were classified as having MCRCC and 30 as other CRCCs, defined as RCCs with extensive cystic change or cystic necrosis. ? Another 22 patients were treated for complex cystic renal masses presumed to be RCC and diagnosed as having benign cyst.

RESULTS

? Benign cysts and MCRCCs were significantly more likely to be of Bosniak classification III than other CRCCs (77% vs 61% vs 27%, P= 0.001). ? The mean Hounsfield unit (HU) during the corticomedullary phase (CMP) was significantly higher in other CRCCs, with HU ≥38 having 83% sensitivity and 80% specificity for predicting other CRCCs. ? In a multiple regression model, Bosniak classification and mean HU during CMP were independent factors predictive of other CRCCs. ? In the 41 patients with masses >4 cm in diameter, the combination of Bosniak classification IV and HU ≥38 during CMP showed 63% sensitivity, 96% specificity, 91% positive predictive value and 80% negative predictive value, yielding 2% false‐positive and 15% false‐negative rates.

CONCLUSIONS

? The mean HU during CMP and Bosniak classification can differentiate MCRCC from other CRCCs. ? This could help in selecting an appropriate surgical method, such as nephron‐sparing surgery, for complex cystic renal masses >4 cm.     

Category migration of renal cystic masses with use of gadolinium-enhanced magnetic resonance imaging

The Bosniak renal cyst classification has been accepted by urologists and radiologists as a way of diagnosing cystic renal masses and determining the management approach. We report two cases of a renal cystic mass that showed a category change from category II on the basis of enhanced computed tomography to category IV after further gadolinium-enhanced magnetic resonance imaging. In both cases, the cysts were later confirmed as kidney cancer by pathology.     

Laparoscopic partial nephrectomy for cystic masses

PURPOSE: Although laparoscopic partial nephrectomy (LPN) has emerged as an effective treatment option in select patients with a solid renal tumor, scant data are available on cystic renal tumors. We report our experience with LPN in 50 patients with a cystic renal lesion. MATERIALS AND METHODS: Of 284 patients undergoing LPN at our institution since August 1999 preoperative computerized tomography identified a suspicious cystic lesion in 50 (17.6%) (group 1). Data were retrospectively compared with those on 50 matched, consecutive patients undergoing LPN for a solid renal mass (group 2). All patients with Bosniak II/IIF cysts were advised to undergo watchful waiting. Surgery was offered if the cyst changed in character or if that was the patient preference. RESULTS: Median tumor size was 3 cm in group 1 and 2.6 cm in group 2 (p = 0.07). Groups 1 and 2 were comparable in regard to perioperative parameters. In patients with Bosniak II (9), IIF (4), III (12) and IV (21) cysts final histopathology revealed renal cell carcinoma in 22%, 25%, 50% and 90%, respectively. All 100 patients had a negative surgical margin. No patient in group 1 had intraoperative puncture/spillage of the cystic tumor. In group 1 during a mean followup of 14 months (range 1 month to 3 years) 1 patient had retroperitoneal recurrence at 1 year despite negative surgical margins during initial LPN. CONCLUSIONS: Surgical outcomes of LPN for suspicious cystic masses are similar to those of LPN for solid tumors. However, extreme caution and refined laparoscopic technique must be exercised to avoid cyst rupture and local spillage.     

Bosniak肾囊性病变分类的临床应用价值

目的 探讨Bosniak分类在肾囊性病变中的临床应用价值.方法 收集2002至2007年手术治疗497例肾囊性病变患者资料.男284例,女213例.平均年龄42岁.病变位于左侧212例,右侧265例,双侧20例.病变直径1.8～11.5 cm,平均5.4 cm.按照Bosniak分类,I类囊肿339例、Ⅱ类49例(其中Ⅱ F 23例)、Ⅲ类44例、Ⅳ类65例.行肾囊肿去顶减压术372例,肾部分切除术51例,根治性肾切除术74例.结果 病理报告为肾恶性肿瘤89例(透明细胞癌74例、乳头状癌12例、低分化癌3例),良性病变408例(单纯囊肿382例、囊肿伴出血6例、囊肿伴感染6例、多房囊性肾瘤5例、纤维囊壁组织9例).I类囊肿中恶性病变3例(O.9%)、Ⅱ类中5例[10.2%,其中非ⅡF为7.7%(2/26),ⅡF为13.O%(3/23)3、Ⅲ类中23例(52.3%)、Ⅳ类中58例(89.2%).组间比较差异有统计学意义(P0.05).403例获随访,随访时间1～5年.75例恶性病变患者中术后1～5年出现肿瘤局部复发和(或)转移9例;328例良性病变中,术后2～5年出现囊肿复发26例.结论 Bosniak分类I类和Ⅱ类肾囊肿一般并不需要积极的外科处理,但ⅡF类囊肿和直径进行性增大以及形态变化明显的囊肿需要引起重视;Ⅲ、Ⅳ类肾囊肿恶变率较高,具备明确手术治疗指征,建议积极处理.     

Extensively Cystic Renal Neoplasms in Adults (Bosniak Classification II or III) – Possible “Common” Histological Diagnoses: Multilocular Cystic Renal Cell Carcinoma,Cystic Nephroma,and Mixed Epithelial and Stromal Tumor of the Kidney

Objective(s): To give an algorithm for resolution of extensively cystic renal neoplasms, preoperatively classified in the Bosniak classification as a category II and III. Methods: From 1991 to 6/2004, 701 patients with 727 renal tumours were surgically treated at our hospital. Extensively cystic tumours were found in 10 cases. Extensively cystic tumours were defined as multicystic tumours without any solid nodules visible neither on CT, nor grossly in the specimen at operation (the Bosniak classification type II or III). Results: Seven multilocular cystic renal cell carcinomas, three mixed epithelial and stromal tumour of the kidney and one cystic nephroma were diagnosed on histology. Conclusion(s): Extensively cystic renal tumours classified as the Bosniak type II or III correspond histologically to the entities mentioned above (multilocular cystic renal cell carcinoma, cystic nephroma, mixed epithelial and stromal tumour of the kidney). These entities cannot be distinguished one from another on preoperative imaging studies. A preoperative biopsy and intra-operative frozen-section analysis do not lead to a correct diagnosis in many cases. Fortunately, the operative strategy is the same for all these tumours. In such cases, the nephron sparing surgery is indicated, whenever technically feasible, as almost all extensively cystic renal tumours have a good prognosis.     

Simple and complex renal cysts in adults: Classification system for renal cystic masses

Ultrasound and slice imaging are currently the key modalities for diagnosing simple renal cysts. Benign simple renal cysts are defined by a set of strict criteria. Any cystic lesions that do not meet these criteria should be classified as “atypical” or “complex” and considered as suspicious. For over three decades, the Bosniak classification has been the central tool for diagnosing renal cystic masses larger than 1 cm. The Bosniak classification is based upon the results of a well-established pre- and post-contrast computed tomography (CT) protocol. Lesions that are difficult to classify or that remain indeterminate after CT can benefit from a multimodal diagnostic approach combining CT, non-contrast-enhanced and contrast-enhanced ultrasound, and magnetic resonance imaging.     

Malignant B-cell lymphoma in renal cyst wall

Renal cysts are frequently found in adults older than 50 years of age. Bosniak type III and IV cysts are commonly associated with malignancy, but most Bosniak I and II lesions are benign, and the optimal management has not been clearly defined. Although computed tomography and ultrasound examinations have improved diagnostic accuracy, some masses will remain indeterminate and require more invasive evaluation. We report a patient with a Bosniak type II renal cyst associated with malignant B-cell lymphoma in the cyst wall diagnosed after laparoscopic renal exploration.     

Laparoscopic deroofing of a renal cyst: the hidden invasion

Cysts of the kidney usually originate from the renal parenchyma after tubule obstruction; rarely pyelocalyceal cysts occur, originating from transitional urothelium. Neoplasia is a rare but possible complication. A 45-year-old man was found to have a cyst related to the right kidney. Computed tomography demonstrated minimal calcification in the wall (Bosniak II). Symptom-relieving percutaneous drainage yielded clear fluid; resultant cytology was negative. After rapid reaccumulation, laparoscopic deroofing was performed. No communication within the renal pelvis was detected however histology revealed transitional cell carcinoma. An open radical nephroureterectomy was performed; adjuvant chemotherapy was given. Three previous cases of malignancy in a pyelocalyceal cyst have been reported. This is the first reported after laparoscopic deroofing of a cyst. Despite widespread use of the Bosniak renal cyst classification, the management of category II cysts remains contentious. This case should serve as a warning to clinicians that seemingly benign cysts of the kidney may harbor underlying neoplasia. Intraoperative frozen section should be considered in all cases where preoperative imaging suggests Bosniak II classification.     

Laparoscopic evaluation of indeterminate renal cysts: long-term follow-up

PURPOSE: We present our long-term follow-up of patients who have undergone laparoscopic evaluation for their indeterminate renal cysts, specifically reporting those patients who were found to have cystic renal-cell carcinoma (RCC) and assessing the safety and efficacy of the procedure. PATIENTS AND METHODS: Fifty-seven patients with indeterminate renal cysts (28 Bosniak category II and 29 Bosniak category III) underwent laparoscopic evaluation between July 1993 and July 2000. A transperitoneal laparoscopic localization and aspiration of the cyst, cytologic analysis, and biopsy of the cyst wall and base were performed. A total of 11 patients were found to have cystic RCC. Patients with malignancy have been followed for a mean of 40 months (range 6-70 months), and five patients had 5 years or more of follow-up. RESULTS: Eleven patients (19% of the total) were found to have cystic RCC. Three of these patients had Bosniak category II cysts, and eight had category III cysts. All tumors were low grade (I or II), and the stages were T1-2, Nx-0, M0. There has been no evidence of laparoscopic port site or renal fossa tumor recurrence, local recurrence, or metastatic disease to date in these patients. There is no cancer-specific mortality. CONCLUSIONS: Long-term follow-up indicates that laparoscopic evaluation of indeterminate renal cysts is not associated with an increased risk of port site or retroperitoneal or peritoneal recurrence of RCC. It may save a patient from undergoing open surgery and should be considered as a diagnostic option for patients with indeterminate renal cysts.     

Surgical Management of Renal Cystic Disease

The kidney is one of the most common sites for cyst in the body (prevalence about 5%). Symptomatic or incidental cyst needs to be characterized further based on Bosniak classification as simple (Bosniak type I & II) or complex (Bosniak type III & IV) cysts with respect to risk of malignancy or other effects on the kidney. The management of simple cysts is entirely for its symptoms or complications (eg, hemorrhage, infection, hydronephrosis, and hypertension). Percutaneous aspiration alone or with sclerotherapy often is the first-line treatment. Surgical decortication generally is reserved for recurrent or very large symptomatic cysts. Laparoscopic surgery is highly efficacious and is associated with high satisfaction rates with minimal morbidity. Retroperitoneal approach is generally preferred, especially in infected or hydatid renal cyst to avoid spillage or contamination of virgin peritoneal cavity. Cyst decortication seems to be an appropriate indication for newer-emerging single-port laparoscopic approaches such as natural orifice transluminal endoscopic surgery, single-incision laparoscopic surgery, or laparoendoscopic single-site surgery. Where available, robot-assisted surgical management can supplant pure laparoscopic management for complex cysts, hydatid cyst, peripelvic cyst, and autosomal dominant polycystic kidney disease without any outstanding benefits, but with added cost, when robot is used.     

Mixed epithelial and stromal tumour of the kidney: imaging features

Study Type – Diagnosis (case series)
Level of Evidence 4

OBJECTIVE

To describe the features on ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MRI) of mixed epithelial and stromal tumours of the kidney.

PATIENTS AND METHODS

Five women with renal mixed epithelial and stromal tumours (mean age 55.6 years, range 49–59) who had preoperative imaging were retrospectively analysed. Three ultrasonograms, five contrast‐enhanced CT scans, and one contrast‐enhanced MRI examination were available for review. Specific imaging features analysed included lesion size, location, enhancement and cystic composition. The presence of calcification, septation, nodularity and a capsule were also evaluated.

RESULTS

All mixed epithelial and stromal tumours appeared as well‐marginated, multi‐septate cystic masses with a nodular component. All lesions were classified as Bosniak category III (three) or IV (two). The presence of calcification (four) or a capsule (three) was variable. Two tumours invaginated into the renal pelvis with no invasion.

CONCLUSION

Mixed epithelial and stromal tumours of the kidney have a diverse radiographic appearance, indistinguishable from multilocular cystic nephroma and cystic renal cell carcinoma.     

Complex renal cyst. Laparoscopic treatment

The difference between the simple renal cysts, that doesn't require surgical treatment, and those that need it, sometimes is difficult. The laparoscopic surgical treatment (laparoscopic cyst decortication -laparoscopic partial nefrectomy or radical laparoscopic nefrectomy) its becoming the gold standard technique, recommending this procedure in Bosniak cyst type III or IV, and in the symptomatic renal cyst type I/II and in any patients with Bosniak cyst renal II. We present a case report in which a renal cell carcinoma was found after laparoscopic cyst decortication of Bosniak cyst type II with laparoscopic radical nefrectomy posteriorly.     

Severe lupus nephritis: importance of re-evaluating the histologic classification and the approach to patient care

The histopathology of severe lupus glomerulonephritis comprises distinct patterns of injury which were initially defined by the World Health Organization Classification of 1982 as focal and segmental glomerulonephritis (category III), diffuse proliferative glomerulonephritis (category IV) and complex membranous glomerulonephritis (categories Vc, Vd). It is assumed that the morphologic abnormalities demonstrated in this classification represent distinctive differences in the mediation of the immune response which leads to a specific type of glomerular inflammation. In 1995 the World Health Organizational committee recommended a change in categorization of focal and segmental glomerulonephritis (class III) and diffuse proliferative glomerulonephritis (class IV), which would overlook the morphological differences between these categories and treat them as a continuum, recommending that biopsies classified as focal and segmental glomerulonephritis (category III) with involvement of > or =50% of glomeruli be included into the diffuse proliferative glomerulonephritis category (category IV). Since the classification of severe lupus nephritis has significant impact on prognosis and the therapeutic approach to patients with this disease, it is the purpose of this review to critically re-examine the existing classification based on new insights into differences in morphologic features and long-term outcome.     

Intrarenal supernumerary ovary excised with partial nephrectomy

Differentiating between complex renal cysts and cystic renal tumors is a difficult task that requires balancing unnecessary surgery with failure to diagnose cancer. We report a case of a Bosniak Class III renal mass removed by partial nephrectomy that was subsequently identified as an intrarenal supernumerary ovary. This report documents the rare anomaly of ectopic ovarian tissue and highlights the extraordinary combination of intrarenal location, lesion complexity, and surgical management with partial nephrectomy that makes this case unique.     

A Retrospective Cohort Study and Clinical Classification System of Acne Keloidalis Nuchae

BACKGROUND: Although many treatments are available for acne keloidalis nuchae (AKN), no systematic classification scheme exists to evaluate the outcomes of these treatments. OBJECTIVE: This study aimed to propose an AKN classification scheme. METHODS: A retrospective data analysis of several parameters, including lesion distribution, lesion type, and scalp disease association, was conducted in 108 men diagnosed with AKN between July 2009 and November 2020 in an outpatient dermatology setting. A three-tier classification system was developed as follows: Tier 1, lesion distribution relative to an area demarcated by two horizontal lines on the occipital prominences and tips of the mastoid processes and lesion sagittal width defined using Classes I through IV; Tier 2, lesion types including papules/nodules (discrete/merged), plaques, and tumorous masses; and Tier 3, the presence or absence of folliculitis decalvans (FD) or dissecting cellulitis (DC). RESULTS: All patients were non-white men, with most being of African (58%) or Hispanic (37%) descent. The most prevalent Tier 1 AKN presentation was Class II (58%). The mean sagittal width for Classes I through III were 2.4cm (I), 4.5cm (II), and 8.0cm (III), with Class IV characterized by widespread scalp disease. Plaques were most common in Tier 2-type lesions. FD or DC was found in seven percent of the study participants. Patients of African descent had a greater tendency to develop tumorous masses (p<0.02). LIMITATIONS: The retrospective study design and possible selection bias. CONCLUSION: We proposed an AKN classification scheme as a tool for objectively describing AKN lesions and evaluating treatment outcomes.