Effects of Y-27632, a Rho-associated Kinase Inhibitor, on Human Corneal Endothelial Cells Cultured by Isolating Human Corneal Endothelial Progenitor Cells

Purpose@#Human corneal endothelial progenitor cells (HCEPs), which has been selectively isolated and differentiated into human corneal endothelial cells (HCECs), are crucial for repairing corneal endothelial damage. In this study, we evaluated the roles of a Rho-assisted kinase (ROCK) inhibitor, Y-27632, on the isolation and expansion of HCEPs, and assessed the in vitro effects of different concentrations of Y-27632 on the differentiated HCEPs. @*Methods@#HCEPs were isolated and expanded in a medium with and without 10μM Y-27632, and then differentiated into HCECs in a medium with fetal bovine serum. The characteristics of HCEPs and differentiated HCEPs were confirmed by immunofluorescence staining. The proliferation, viability, morphology, and wound-healing ability of differentiated HCEPs were assessed in the presence of different concentrations of Y-27632. @*Results@#Y-27632 enabled the isolation and expansion of HCEPs from the corneal endothelium. The differentiated HCEPs showed an optimal increase in proliferation and survival in the presence of 10μM Y-27632. As the concentration of Y-27632 increased, differentiated HCEPs became elongated, and actin filaments were redistributed to the periphery of cells. Y-27632 also caused a concentration-dependent enhancement in the wound-healing ability of differentiated HCEPs. @*Conclusions@#Y-27632 enabled the isolation and expansion of HCEPs. It also enhanced the proliferation, viability, and migration of differentiated HCEPs.

Baseline Clinical and Biomarker Characteristics of Biobank Innovations for Chronic Cerebrovascular Disease With Alzheimer’s Disease Study: BICWALZS

Objective@#We aimed to present the study design and baseline cross-sectional participant characteristics of biobank innovations for chronic cerebrovascular disease with Alzheimer’s disease study (BICWALZS) participants. @*Methods@#A total of 1,013 participants were enrolled in BICWALZS from October 2016 to December 2020. All participants underwent clinical assessments, basic blood tests, and standardized neuropsychological tests (n=1,013). We performed brain magnetic resonance imaging (MRI, n=817), brain amyloid positron emission tomography (PET, n=713), single nucleotide polymorphism microarray chip (K-Chip, n=949), locomotor activity assessment (actigraphy, n=200), and patient-derived dermal fibroblast sampling (n=175) on a subset of participants. @*Results@#The mean age was 72.8 years, and 658 (65.0%) were females. Based on clinical assessments, total of 168, 534, 211, 80, and 20 had subjective cognitive decline, mild cognitive impairment (MCI), Alzheimer’s dementia, vascular dementia, and other types of dementia or not otherwise specified, respectively. Based on neuroimaging biomarkers and cognition, 199, 159, 78, and 204 were cognitively normal (CN), Alzheimer’s disease (AD)-related cognitive impairment, vascular cognitive impairment, and not otherwise specified due to mixed pathology (NOS). Each group exhibited many differences in various clinical, neuropsychological, and neuroimaging results at baseline. Baseline characteristics of BICWALZS participants in the MCI, AD, and vascular dementia groups were generally acceptable and consistent with 26 worldwide dementia cohorts and another independent AD cohort in Korea. @*Conclusion@#The BICWALZS is a prospective and longitudinal study assessing various clinical and biomarker characteristics in older adults with cognitive complaints. Details of the recruitment process, methodology, and baseline assessment results are described in this paper.

Poorly differentiated thyroid carcinoma: An institutional experience

Purpose@#The incidence of poorly differentiated thyroid carcinoma (PDTC) is extremely low among thyroid cancers and there is no standardized treatment guideline for it. In this study, we have analyzed PDTC patients and reviewed their clinicopathological features. @*Methods@#Data of PDTC patients from our institution are collected through the electronic medical database. We analyzed them by several parameters such as basic demographics, presenting symptom, preoperative cytology results, associated pathology, surgical results, surgery type, and distant metastasis. @*Results@#We collected 23 cases in our institution. Apart from two patients who were transferred to another hospital upon diagnosis, all 21 operated cases are analyzed. The parameters we studied were age, sex, presenting symptoms, distant metastasis and pathological features such as tumor size, associated pathology, predominant pattern and so on. We also provided descriptive analyses according to the type of presentation and treatment; patients with distant metastasis, juvenile cancer, and concurrent hyperthyroidism. Furthermore, we provided different cases in which the initial surgical plans differed. @*Conclusion@#We present 21 cases of PDTC patients and clarify their clinicopathological features. Despite some limitations, this study may shed light for future research regarding treatment of PDTC patients.

Primary carcinoid tumor in the external auditory canal

A 39-year-old man visited the department of otolaryngology due to an ongoing hearing disturbance that had lasted for 1 year. Temporal bone computed tomography revealed soft tissue density nearly obliterating the left external auditory canal (EAC). The mass was composed of sheets of round tumor cells containing moderate amounts of fine granular cytoplasm and salt and pepper chromatin. Neither mitosis nor necrosis was found. The Ki-67 proliferation index was less than 2%. Cells were positive for CD56 and synaptophysin but negative for chromogranin, cytokeratin (CK) 20, and CK7. Based on these findings, the tumor was diagnosed as a carcinoid tumor, well differentiated neuroendocrine carcinoma, grade 1 (G1) according to current World Health Organization (WHO) classification of head and neck tumors; and a neuroendocrine tumor, G1 according to neuroendocrine neoplasm (NEN)-2018 WHO standard classification. He remained free of local recurrence and metastasis after 20 months of follow up. To date, only six cases of primary NENs in the EAC have been reported. Metastatic tumor should be included in the differential diagnoses. Because of its rarity, the prognosis and treatment have not yet been clarified.

Contribution of cytologic examination to diagnosis of poorly differentiated thyroid carcinoma

Background@#The cytologic diagnosis of poorly differentiated thyroid carcinoma (PDTC) is difficult because it lacks salient cytologic findings and shares cytologic features with more commonly encountered neoplasms. Due to diverse cytologic findings and paucicellularity of PDTC, standardization of cytologic diagnostic criteria is limited. The purpose of this study is to investigate and recognize diverse thyroid findings of fine needle aspiration (FNA) cytology and frozen smear cytology in diagnosis of this rare but aggressive carcinoma. @*Methods@#The present study included six cases of FNA cytology and frozen smears of histologically diagnosed PDTCs. @*Results@#PDTC showed cytologic overlap with well-differentiated thyroid carcinomas (WDTCs). Five of six cases showed dedifferentiation arising from well differentiated thyroid carcinomas. Only one de novo PDTC showed highly cellular smears composed of discohesive small cells, high nuclear/cytoplasmic (N/C) ratio, prominent micronucleoli, and irregular nuclei. Retrospectively reviewed, these findings are highly suspicious for PDTC. Cytologic findings of nuclear atypia, pleomorphism, and irregularity were frequently found, whereas scattered small cells were seen only in the de novo case. @*Conclusions@#Heterogeneous cytologic findings of PDTCs are shared with those of WDTCs and contribute to difficult preoperative cytologic diagnoses. Most PDTCs show dedifferentiation from WDTCs. Albeit rare, de novo PDTC should be considered with cytology showing discohesive small cells with high N/C ratio. This will enable precise diagnosis and prompt treatment of this aggressive malignancy

Adjunctive markers for classification and diagnosis of central nervous system tumors: results of a multi-center neuropathological survey in Korea

Background@#The revised 4th 2016 World Health Organization (WHO) classification of tumors of the central nervous system (CNS) classification has adopted integrated diagnosis encompassing the histology and molecular features of CNS tumors. We aimed to investigate the immunohistochemistry, molecular testing, and testing methods for diagnosis of CNS tumors in pathological labs of tertiary centers in Korea, and evaluate the adequacy of tests for proper diagnosis in daily practice. @*Methods@#A survey, composed of eight questions concerning molecular testing for diagnosis of CNS tumors, was sent to 10 neuropathologists working in tertiary centers in Korea. @*Results@#For diagnosis of astrocytic and oligodendroglial tumors, all 10 centers performed isocitrate dehydrogenase mutations testing and 1p/19q loss of heterozygosity. For glioneuronal tumors, immunohistochemistry (IHC) assays for synaptophysin (n = 9), CD34 (n = 7), BRAF(VE1) (n = 5) were used. For embryonal tumors, particularly in medulloblastoma, four respondents used IHC panel (growth factor receptor bound protein 2-associated protein 1, filamin A, and yes-associated protein 1) for molecular subclassification. Regarding meningioma, all respondents performed Ki-67 IHC and five performed telomerase reverse transcriptase promoter mutation. @*Conclusions@#Most tertiary centers made proper diagnosis in line with 2016 WHO classification. As classification of CNS tumors has evolved to be more complex and more ancillary tests are required, these should be performed considering the effect of necessity and justification.

Pediatric granular cell tumor in the posterior wall of the larynx extending to the trachea

Granular cell tumor (GCT) is a slow-growing benign neoplasm that can be found in any organ. Pediatric laryngotracheal GCT is rare. We experienced a 6-year-old boy suffering from a barking cough and symptoms of stridor and croup for one month. Head and neck computed tomography revealed a protruding mass that occluded 60% of the airway lumen. Under the impression of hemangioma or papilloma, excision revealed a submucosal non-encapsulated mass. Histologically, the mass was composed of sheets of large polyhedralshaped tumor cells containing plump eosinophilic granular cytoplasm and centrally placed, small, bland-appearing nuclei. The tumor cells were positive for S-100 protein, and voluminous eosinophilic cytoplasm was stained by diastase-resistant periodic acid-Schiff. The present report describes a unique case of a huge pediatric laryngeal GCT extending to the subglottic trachea. We also review the clinical course of pediatric laryngotracheal GCT and emphasize the importance of diagnosing GCT in children.

Comparison of papanicolaou smear and human papillomavirus (HPV) test as cervical screening tools: can we rely on HPV test alone as a screening method? An 11-year retrospective experience at a single institution

Background@#The decrease in incidence of cervical dysplasia and carcinoma has not been as dramatic as expected with the development of improved research tools and test methods. The human papillomavirus (HPV) test alone has been suggested for screening in some countries. The National Cancer Screening Project in Korea has applied Papanicolaou smears (Pap smears) as the screening method for cervical dysplasia and carcinoma. We evaluated the value of Pap smear and HPV testing as diagnostic screening tools in a single institution. @*Methods@#Patients co-tested with HPV test and Pap smear simultaneously or within one month of each other were included in this study. Patients with only punch biopsy results were excluded because of sampling errors. A total of 999 cases were included, and the collected reports encompassed results of smear cytology, HPV subtypes, and histologic examinations. @*Results@#Sensitivity and specificity of detecting high-grade squamous intraepithelial lesion (HSIL) and squamous cell carcinoma (SCC) were higher for Pap smears than for HPV tests (sensitivity, 97.14%; specificity, 85.58% for Pap smears; sensitivity, 88.32%; specificity, 54.92% for HPV tests). HPV tests and Pap smears did not differ greatly in detection of low-grade squamous intraepithelial lesion (85.35% for HPV test, 80.31% for Pap smears). When atypical glandular cells were noted on Pap smears, the likelihood for histologic diagnosis of adenocarcinoma following Pap smear was higher than that of high-risk HPV test results (18.8 and 1.53, respectively). @*Conclusions@#Pap smears were more useful than HPV tests in the diagnosis of HSIL, SCC, and glandular lesions.

Associations between the Munk Score and Tear Film Scan Revealed byCorneal Topography after Dacryocystorhinostomy

Purpose@#We evaluated changes in the tear film parameters of the corneal surface, and their correlations with Munk scores,based on corneal topographic scans of patients with nasolacrimal duct obstructions who underwent dacryocystorhinostomy(DCR). We explored whether tear parameters can serve as useful indicators of functional surgical success. @*Methods@#We assessed 72 eyes of 45 patients diagnosed with nasolacrimal duct obstruction who underwent DCR. Tear film parameterswere measured via corneal topography (Keratograph® 5M) once before, and three times after surgery, and includedtear meniscus height (TMH), and the initial and average keratographic tear break-up time (NIKBUT-first and NIKBUT-average,respectively; measured noninvasively). @*Results@#The three postoperative TMH values were 0.31 ± 0.20, 0.30 ± 0.22, and 0.29 ± 0.15 mm, all of which were significantlylower than the preoperative value of 0.48 ± 0.29 mm (all, p 0.999).Changes in the Munk score after surgery correlated significantly with changes in the TMH (r = 0.46, p < 0.001). When functionalsuccess was defined as a Munk score ≤ 1, the area under the curve (AUC) value corresponding to the ability of TMH to definefunctional success of 0.995, was statistically significant (cut-off of 0.31 mm; p < 0.001). @*Conclusions@#The TMH DCR correlated significantly with the Munk score, which is a quantitative measure of clinical symptomseverity. The ability of TMH to define functional surgical success was excellent.

Intraoperative frozen cytology of intraosseous cystic meningioma in the sphenoid bone

Meningiomas in bone are rarely subjected to fine-needle aspiration diagnosis, and those arising in the skull bone with a cystic presentation are rare. A 24-year-old woman presented with subdural hemorrhage, and subsequent radiology depicted an osteolytic mass-like lesion in the sphenoid bone. Intraoperatively, a solid and cystic hemorrhagic lesion mimicking an aneurysmal bone cyst was observed in the sphenoid bone with dural tearing. Frozen cytology showed singly scattered or epithelioid clusters of round to elongated cells intermixed with many neutrophils. Tumor cells had bland-looking round nuclei with rare prominent nucleoli and nuclear inclusions and eosinophilic granular to globoid cytoplasm in capillary-rich fragments. Histology revealed intraosseous meningothelial and microcystic meningioma (World Health Organization grade 1) in right lesser wing of the sphenoid bone. Considering its unusual location and cytologic findings, differential diagnoses included chordoma, chondroma, chondrosarcoma, and aneurysmal bone cyst. The present case posed a diagnostic challenge due to possible confusion with these entities.

Intraoperative frozen cytology of intraosseous cystic meningioma in the sphenoid bone

Meningiomas in bone are rarely subjected to fine-needle aspiration diagnosis, and those arising in the skull bone with a cystic presentation are rare. A 24-year-old woman presented with subdural hemorrhage, and subsequent radiology depicted an osteolytic mass-like lesion in the sphenoid bone. Intraoperatively, a solid and cystic hemorrhagic lesion mimicking an aneurysmal bone cyst was observed in the sphenoid bone with dural tearing. Frozen cytology showed singly scattered or epithelioid clusters of round to elongated cells intermixed with many neutrophils. Tumor cells had bland-looking round nuclei with rare prominent nucleoli and nuclear inclusions and eosinophilic granular to globoid cytoplasm in capillary-rich fragments. Histology revealed intraosseous meningothelial and microcystic meningioma (World Health Organization grade 1) in right lesser wing of the sphenoid bone. Considering its unusual location and cytologic findings, differential diagnoses included chordoma, chondroma, chondrosarcoma, and aneurysmal bone cyst. The present case posed a diagnostic challenge due to possible confusion with these entities.

Primary Necrobiotic Xanthogranulomatous Sialadenitis with Submandibular Gland Localization without Skin Involvement

Necrobiotic xanthogranulomatous reaction is a multiorgan, non-Langerhans cell histiocytosis with an unknown etiology. Occurrence in the salivary gland is extremely rare. We recently identified a case of necrobiotic xanthogranulomatous sialadenitis in a 73-year-old Korean woman who presented with a painless palpable lesion in the chin. There was no accompanying cutaneous lesion. Partial resection and subsequent wide excision with neck dissection were performed. Pathological examination showed a severe inflammatory lesion that included foamy macrophages centrally admixed with neutrophils, eosinophils, lymphocytes, plasma cells, and scattered giant cells, as well as necrobiosis. During the 12-month postoperative period, no grossly remarkable change in size was noted. Necrobiotic xanthogranulomatous inflammation may be preceded by or combined with hematologic malignancy. Although rare, clinicians and radiologists should be aware that an adhesive necrobiotic xanthogranuloma in the salivary gland may present with a mass-like lesion. Further evaluation for hematologic disease and close follow-up are needed when a pathologic diagnosis is made.

Frozen Cytology of Meningeal Malignant Solitary Fibrous Tumor/Hemangiopericytoma

A 51-year-old woman presented with severe dizziness. The brain magnetic resonance image revealed a 5.5 cm multiloculated mass with a thick rim in the left temporal lobe. Cytological examination of frozen diagnosis of the mass showed hypercellular sheets of round and rhabdoid cells in a hemorrhagic background, and two mitotic figures were observed. Histologically, the excised dura-based mass consisted of predominantly round cells with small foci of rhabdoid tumor cells in a pseudoalveolar pattern in a hemorrhagic background, and the cells showed nuclear positivity for signal transducer and activator of transcription 6 as well as frequent mitosis. The mass was diagnosed as a grade 3 solitary fibrous tumor (SFT)/hemangiopericytoma (HPC). The cytological diagnosis of SFT/HPC is challenging because of the heterogeneous cytological findings, such as histological heterogeneity, and because there are no standardized cytological criteria for malignant SFT/HPC. Cytological findings, such as singly scattered small cells, hypercellularity, rare ropy collagen, and round and rhabdoid cells with pseudoalveolar pattern, may assist in the diagnosis of malignant SFT/HPC.

Intraoperative Frozen Cytology of Central Nervous System Neoplasms: An Ancillary Tool for Frozen Diagnosis

BACKGROUND: Pathologic diagnosis of central nervous system (CNS) neoplasms is made by comparing light microscopic, immunohistochemical, and molecular cytogenetic findings with clinicoradiologic observations. Intraoperative frozen cytology smears can improve the diagnostic accuracy for CNS neoplasms. Here, we evaluate the diagnostic value of cytology in frozen diagnoses of CNS neoplasms. METHODS: Cases were selected from patients undergoing both frozen cytology and frozen sections. Diagnostic accuracy was evaluated. RESULTS: Four hundred and fifty-four cases were included in this retrospective single-center review study covering a span of 10 years. Five discrepant cases (1.1%) were found after excluding 53 deferred cases (31 cases of tentative diagnosis, 22 cases of inadequate frozen sampling). A total of 346 cases of complete concordance and 50 cases of partial concordance were classified as not discordant cases in the present study. Diagnostic accuracy of intraoperative frozen diagnosis was 87.2%, and the accuracy was 98.8% after excluding deferred cases. Discrepancies between frozen and permanent diagnoses (n = 5, 1.1%) were found in cases of nonrepresentative sampling (n = 2) and misinterpretation (n = 3). High concordance was observed more frequently in meningeal tumors (97/98, 99%), metastatic brain tumors (51/52, 98.1%), pituitary adenomas (86/89, 96.6%), schwannomas (45/47, 95.8%), high-grade astrocytic tumors (47/58, 81%), low grade astrocytic tumors (10/13, 76.9%), non-neoplastic lesions (23/36, 63.9%), in decreasing frequency. CONCLUSIONS: Using intraoperative cytology and frozen sections of CNS tumors is a highly accurate diagnostic ancillary method, providing subtyping of CNS neoplasms, especially in frequently encountered entities.

Squamous Cell Carcinoma of the Extrahepatic Common Hepatic Duct

We report a rare case of hilar squamous cell carcinoma. A 62-year-old Korean woman complaining of nausea was referred to our hospital. Her biliary computed tomography revealed a 28 mm-sized protruding solid mass in the proximal common bile duct. The patient underwent left hemihepatectomy with S1 segmentectomy and segmental excision of the common bile duct. Microscopically, the tumor was a moderately differentiated squamous cell carcinoma of the extrahepatic bile duct, without any component of adenocarcinoma or metaplastic portion in the biliary epithelium. Immunohistochemically, the tumor was positive for cytokeratin (CK) 5/6, CK19, p40, and p63. Squamous cell carcinoma of the extrahepatic bile duct is rare. To date, only 24 cases of biliary squamous cell carcinomas have been reported. Here, we provide a clinicopathologic review of previously reported extrahepatic bile duct squamous cell carcinomas.

Forehead-supporting chair system for follicular unit extraction hair transplantation

The seated and prone positions are the most common surgical positions used during follicular unit extraction (FUE). Compared to the latter, the former eases centering and enables more optimal surgical field exposure due to gravitational effects on intraoperative bleeding. Furthermore, the surgeon can simultaneously work with multiple assistants, increasing efficiency and reducing operative time. During the harvesting stage of FUE, the patient is often seated in an electric height-adjustable salon chair. Such equipment, however, does not provide support for the head; maintaining a fixed upright position for an extremely long-lasting and delicate surgery that requires loupes with ×5 or higher magnification is challenging for both the surgeon and the patient. On the other hand, a support system that firmly fixes the patient's forehead would have ergonomic benefits during the process of FUE donor harvesting in a seated position. Firm support of the forehead would also enable upward traction to provide tension on the scalp, lessen the gap between the hair exit angle and internal hair angle, and reduce graft torsion, ultimately minimizing follicular injury and optimizing graft quality.

Detection of Recurrent/Residual Hepatocellular Carcinoma: Single-Center Retrospective Comparative Study Between Parenchymal Blood Volume Mapping Using Cone Beam CT and Multiphase Dynamic CT

PURPOSE@#To evaluate the usefulness of cone beam computed tomography (CT)-based parenchymal blood volume (PBV) mapping for the detection of marginal recurrence or residual hepatocellular carcinoma, after transcatheter arterial chemoembolization (TACE), and to compare it with multiphase dynamic CT (MDCT).@*MATERIALS AND METHODS@#From March 2015 to October 2016, 26 patients with 49 iodized nodules who underwent TACE and a pre-interventional MDCT scan were enrolled in our study. We evaluated the diagnostic efficacies of PBV mapping using cone beam CT and MDCT in the detection of marginal recurrences or viable tumors.@*RESULTS@#The sensitivity, specificity, positive predictive value, and negative predictive value (NPV) of PBV mapping and MDCT were 100%, 96.7%, 94.7%, and 100%, and 77.9%, 93.5%, 87.5%, and 87.8%, respectively. The overall sensitivity for identifying local marginal recurrence was higher for PBV mapping than for MDCT (p < 0.005). The performances of PBV mapping and MDCT in the diagnosis of local marginal recurrence were significantly different (p = 0.037, McNemar test).@*CONCLUSION@#Compared with MDCT, PBV mapping can significantly increase the detection of marginal recurrence or residual tumor after TACE because it is free of beam-hardening artifact. PBV mapping should be considered as a feasible modality-related tool for patients who have undergone chemoembolization.

Post-transplant Amputation Traumatic Neuroma of the Hilum and Extrahepatic Duct in a Liver Donor

No abstract available.

Malignant Transformation of Craniopharyngioma without Radiation Therapy: Case Report and Review of the Literature

Craniopharyngiomas exhibiting histologic malignancy are extremely rare. Herein, we report the case of a 26-year-old male patient who underwent suprasellar mass excision via an interhemispheric transcallosal approach. Histopathological examination indicated that the craniopharyngioma was of the adamantinomatous subtype. The patient received postoperative medical treatment for endocrine dysfunction and diabetes mellitus without radiation treatment. Two years after the operation, he presented with progressive visual disturbance and altered mentality. Magnetic resonance imaging revealed a huge mass in the suprasellar cistern and third ventricle. He underwent a second operation via the same approach. The histopathological examination showed an adamantinomatous craniopharyngioma with sheets of solid proliferation in a spindled pattern, indicating malignant transformation. Malignant transformation of craniopharyngioma in the absence of radiation therapy has been reported in only five cases, including this one. We present a case of malignant transformation of craniopharyngioma with a brief review of relevant literature.

Photo Epilation with Intense Pulsed Light for Thinning of Anterior Hairline after Hairline Correction Surgery in East Asians

BACKGROUND: Thin hairs are critical to achieve natural result in female hairline correction surgery. However, there are few studies on the usefulness of hair thinning by intense pulsed light (IPL) after hairline correction surgery in East Asian females. METHODS: Hair thinning using IPL was performed in 54 women who had complained about thick hairs along the frontal hairline after hairline correction surgery. Patient mean age was 31.2 years old and patients were an average of 2.1 years post-hairline correction surgery. Initial treatment used 10 J, while second and third sessions were conducted with 10 to 15 J according to responsiveness to treatment. RESULTS: Mean thickness of individual hairs assessed before the procedure was 78.86 µm. The mean number of procedures was 1.6 per patient. Forty of 54 subjects (74%) achieved satisfactory hair thinning with only one procedure from 78.01 to 66.14 µm after treatment. The measured thickness was 66.43 µm at the end of the first year in patients who were satisfied after one procedure. Thirteen cases achieved satisfactory hair thinning after two sessions. Mean thickness was 74.44 µm and 67.51 µm, before and after the second session. One case required a third session with 15J, thinning from 89.00 to 66.50 µm. CONCLUSIONS: Hair thinning by IPL is a very useful method to provide a natural look after hairline correction surgery in East Asians, who have naturally thick hair.