Stricturing Crohn's Disease Single-Cell RNA Sequencing Reveals Fibroblast Heterogeneity and Intercellular Interactions.

BACKGROUND & AIMS: Fibroblasts play a key role in stricture formation in Crohn's disease (CD) but understanding its pathogenesis requires a systems-level investigation to uncover new treatment targets. We studied full-thickness CD tissues to characterize fibroblast heterogeneity and function by generating the first single-cell RNA sequencing (scRNAseq) atlas of strictured bowel and providing proof of principle for therapeutic target validation. METHODS: We performed scRNAseq of 13 fresh full-thickness CD resections containing noninvolved, inflamed nonstrictured, and strictured segments as well as 7 normal non-CD bowel segments. Each segment was separated into mucosa/submucosa or muscularis propria and analyzed separately for a total of 99 tissue samples and 409,001 cells. We validated cadherin-11 (CDH11) as a potential therapeutic target by using whole tissues, isolated intestinal cells, NanoString nCounter, next-generation sequencing, proteomics, and animal models. RESULTS: Our integrated dataset revealed fibroblast heterogeneity in strictured CD with the majority of stricture-selective changes detected in the mucosa/submucosa, but not the muscle layer. Cell-cell interaction modeling revealed CXCL14+ as well as MMP/WNT5A+ fibroblasts displaying a central signaling role in CD strictures. CDH11, a fibroblast cell-cell adhesion molecule, was broadly expressed and up-regulated, and its profibrotic function was validated using NanoString nCounter, RNA sequencing, tissue target expression, in vitro gain- and loss-of-function experiments, proteomics, and knock-out and antibody-mediated CDH11 blockade in experimental colitis. CONCLUSIONS: A full-thickness bowel scRNAseq atlas revealed previously unrecognized fibroblast heterogeneity and interactions in CD strictures and CDH11 was validated as a potential therapeutic target. These results provide a new resource for a better understanding of CD stricture formation and open potential therapeutic developments. This work has been posted as a preprint on Biorxiv under doi: 10.1101/2023.04.03.534781.

A Different Way to Think About Syndromes of Hereditary Colorectal Cancer.

BACKGROUND: Hereditary colorectal cancer is an increasingly complex field in which the commoner syndromes are being augmented by rarer genetic presentations contributing to familial polyposis and colorectal cancer. Coming to grips with the complexity is difficult because of the phenotypic and genotypic overlap between syndromes. OBJECTIVE: This study aimed to describe a new way of thinking about syndromes of hereditary colorectal cancer based on their embryonic tissue of origin. DATA SOURCES: Articles were searched through PubMed and MEDLINE. STUDY SELECTION: The terms "hereditary colorectal cancer," "syndromes of hereditary colorectal cancer," and "hereditary polyposis" were used to direct the search. RESULTS: Primarily endoderm-derived syndromes were different from mesoderm-derived syndromes in their genetics, molecular biology, histology, and clinical course. LIMITATIONS: There is considerable phenotypic and genotypic overlap between syndromes, even when considering embryonic tissue of origin. CONCLUSIONS: Thinking about hereditary syndromes of colorectal cancer from the perspective of embryonic tissue of origin provides a fresh look at phenotype and genotype that opens new areas of exploration. UNA FORMA DIFERENTE DE PENSAR SOBRE LOS SNDROMES DEL CNCER COLORRECTAL HEREDITARIO: ANTECEDENTES:El cáncer colorrectal hereditario es un campo cada vez más complejo donde los síndromes más comunes se ven aumentados por presentaciones genéticas más raras que contribuyen a la poliposis familiar y al cáncer colorrectal. Hacer frente a esta complejidad resulta difícil debido a la superposición fenotípica y genotípica entre los síndromes.OBJETIVO:En este artículo, describimos una nueva forma de pensar sobre los síndromes de cáncer colorrectal hereditario en función del origen de su tejido embrionario.FUENTES DE DATOS:Se realizaron búsquedas de artículos en Pubmed y Medline.SELECCIÓN DE ESTUDIOS:Se utilizaron los términos "cáncer colorrectal hereditario", "síndromes de cáncer colorrectal hereditario", "poliposis hereditaria" para dirigir la búsqueda.RESULTADOS:Principalmente los síndromes derivados del endodermo fueron diferentes a los síndromes derivados del mesodermo en su genética, biología molecular, histología y curso clínico.LIMITACIONES:Existe una superposición fenotípica y genotípica considerable entre los síndromes, incluso cuando se considera el tejido de origen embrionario.CONCLUSIÓN:Pensar en los síndromes hereditarios del cáncer colorrectal desde la perspectiva del tejido embrionario de origen proporciona una nueva mirada al fenotipo y al genotipo que abre nuevas áreas de exploración. (Traducción-Dr Osvaldo Gauto ).

The location of premalignant colorectal polyps under age 50: a further rationale for screening sigmoidoscopy.

PURPOSE: The incidence of colorectal cancer (CRC) among young adults has been dramatically rising, with guidelines for screening recently adjusted to start at age 45. However, knowledge of the precursor lesions is limited. We recently reported that 83% of CRC diagnosed under age 50 are left sided. Our aim was to analyze the location and histology of benign colorectal lesions found in a cohort of patients younger than 50, documenting the presence of advanced histology. METHODS: We used the database in the Department of Pathology to retrospectively review the location and histology of all benign colorectal neoplasms in patients under age 50 submitted to pathology examination during 2006-2016. RESULTS: A total of 8364 lesions were examined from 4773 patients, and 3534 (65.5%) of the patients had only one polyp and the rest had multiple. Mean age was 41.9 years (range 16-49) while 3843 (72.8%) of the patients were between the ages of 40 and 49. In total, 4570/8364 lesions (54.6%) were distal to the splenic flexure. The most common pathology was tubular adenoma (63.7%), then hyperplastic polyps (16.6%), sessile serrated lesions (SSLs) (13.1%), and tubulovillous adenomas (6.3%). Tubulovillous adenomas, villous lesions, advanced adenomas, and adenomas with high-grade dysplasia were all predominantly left sided (left colon and rectum = 77.6%, 85%, 78.3%, and 87.6% respectively). Of the SSLs, 71.5% were in the right colon while 16.6% of hyperplastic lesions were right sided. CONCLUSIONS: High-risk advanced adenomas are predominantly left sided. This focuses attention on the rectum and left colon where carcinogenesis is strong in the young.

A Review of Autoimmune Enteropathy and Its Associated Syndromes.

Autoimmune enteropathy is an extremely rare condition characterized by an abnormal intestinal immune response which typically manifests within the first 6 months of life as severe, intractable diarrhea that does not respond to dietary modification. Affected individuals frequently present with other signs of autoimmunity. The diagnosis is made based on a characteristic combination of clinical symptoms, laboratory studies, and histological features on small bowel biopsy. Autoimmune enteropathy is associated with a number of other conditions and syndromes, most notably immunodysregulation polyendocrinopathy enteropathy X-linked (IPEX) syndrome and autoimmune polyglandular syndrome type 1 (APS-1). Diagnosis and treatment is challenging, and further research is needed to better understand the pathogenesis, disease progression, and long-term outcomes of these conditions.

Mucinous Histology Signifies Poor Oncologic Outcome in Young Patients With Colorectal Cancer.

BACKGROUND: The incidence of colorectal cancer in the young (under age 40) is increasing, and this population has worse oncologic outcomes. Mucinous histology is a potential prognostic factor in colorectal cancer, but has not been evaluated specifically in young patients. OBJECTIVE: The objective of the study was to determine factors associated with poor outcome in young patients with colorectal cancer (≤40 years) and to determine relationships between mucinous histology and oncologic outcomes in this population. DESIGN: This is a retrospective study. SETTING: Patients from a single-institution tertiary care center were studied. PATIENTS: A total of 224 patients with colorectal cancer under 40 years of age diagnosed between 1990 and 2010 were included (mean age, 34.7 years; 51.3% female). 34 patients (15.2%) had mucinous histology. INTERVENTIONS(S): There were no interventions. MAIN OUTCOME MEASURES: Oncologic outcomes were analyzed according to the presence of mucinous histology. RESULTS: The mucinous and nonmucin colorectal cancer study populations were statistically similar in age, sex, tumor location, pathological stage, differentiation, and adjuvant chemotherapy use. Five-year disease-free survival was 29.1% versus 71.3% (p < 0.0001) and 5-year overall survival was 54.7% versus 80.3% (p < 0.0001) for mucinous and nonmucinous patients, respectively. Mucinous colorectal cancers recurred earlier at a median time of 36.4 months versus 94.2 months for nonmucin colorectal cancers (p < 0.001). On multivariate analysis, pathological stage (stage II HR, 3.61; 95% CI, 1.37-9.50; stage III HR, 5.27; 95% CI, 2.12-12.33), positive margins (HR, 1.95; 95% CI, 1.12-3.23), angiolymphatic invasion (HR, 2.15; 95% CI, 1.26-3.97), and mucinous histology (HR, 2.36; 95% CI, 1.44-3.96) were independently associated with worse disease-free and overall survival. LIMITATIONS: This is a retrospective study without genetic information. CONCLUSIONS: Mucinous histology is a negative prognostic factor in young patients with colorectal cancer. This is associated with early and high recurrence rates, despite use of standard neoadjuvant and adjuvant regimens. Physicians need to be aware of this association and potentially explore novel treatment options. See Video Abstract at http://links.lww.com/DCR/A575.

Microanatomical Location of Hyaluronic Acid Gel Following Injection of the Upper Lip Vermillion Border: Comparison of Needle and Microcannula Injection Technique.

PURPOSE: To compare needle and microcannula injection techniques in regards to the microanatomical location of hyaluronic acid (HA) gel injected in the upper lip vermillion border of cadaver specimens. METHODS: The upper lip vermillion border was injected transcutaneously with HA gel in 8 fresh hemifaces of 4 female human cadavers. Each hemiface was injected by a single experienced injector, the right side using a 27-gauge microcannula and the left side using a 30-gauge needle. A 2-cm region of each lip was excised lateral to a point 1-cm lateral to the philtrum. Specimens were fixed in 95% alcohol, embedded in paraffin, and stained with hematoxylin-eosin for histologic examination. RESULTS: Most HA injected with either a needle or a microcannula was located within the orbicularis oris muscle, and the remaining HA resided within the subcutaneous fat. In 3/4 right (microcannula) hemifaces, 100% of the HA was located within the muscle. Only 2/4 left (needle) hemifaces had at least 95% of the HA located within the muscle. Overall, in right (microcannula) hemifaces, 93% of the filler was located within the muscle, and in left (needle) hemifaces, 79% of the filler was located within the muscle (p =0.14). CONCLUSIONS: Most HA filler injected into the vermillion border after either microcannula or needle injection resides within the orbicularis oris muscle rather than in a subcutaneous/submucosal location. Injection with a microcannula shows a trend for more uniform intramuscular location compared with needle injection.

Deoxycholic Acid and the Marginal Mandibular Nerve: A Cadaver Study.

BACKGROUND: One of the rare but serious complications observed with deoxycholic acid administration is damage to the marginal mandibular nerve. In this study, we evaluated if deoxycholic acid directly induces histologic damage to fresh cadaveric marginal mandibular nerve. METHODS: A segment of marginal mandibular nerve was harvested from 12 hemifaces of 6 fresh cadavers. The nerve specimen was exposed to either 0.9% sterile saline for 24 h, deoxycholic acid (10 mg/ml) for 20 min, or deoxycholic acid (10 mg/ml) for 24 h. The nerve specimens were then fixed in glutaraldehyde for a minimum of 24 h. Toluidine blue stained sections were evaluated for stain intensity using light microscopy and color deconvolution image analysis. Supraplatysmal fat was harvested as a positive control and exposed to the same treatments as the marginal mandibular nerve specimens, then evaluated using transmission electron microscopy. RESULTS: Toluidine blue staining was less in the marginal mandibular nerve exposed to deoxycholic acid when compared to saline. The specimen exposed to deoxycholic acid for 24 h showed less toluidine blue staining than that of the nerve exposed to deoxycholic acid for 20 min. Transmission electron microscopy of submental fat exposed to deoxycholic acid revealed disruption of adipocyte cell membrane integrity and loss of cellular organelles when compared to specimens only exposed to saline. CONCLUSIONS: Deoxycholic acid (10 mg/ml) damages the marginal mandibular nerve myelin sheath in fresh human cadaver specimens. Direct deoxycholic acid neurotoxicity may cause marginal mandibular nerve injury clinically. NO LEVEL ASSIGNED: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Biopsy Specimens From Allograft Liver Contain Histologic Features of Hepatitis C Virus Infection After Virus Eradication.

BACKGROUND & AIMS: Most patients, even those who have received a liver transplant, achieve a sustained virologic response (SVR) to therapy for hepatitis C virus (HCV) infection. Little is known about the histologic features of liver biopsy specimens collected after SVR, particularly in patients who have received a liver transplant. We aimed to better characterize the histologic features of allograft liver biopsy specimens from patients who achieved SVR to anti-HCV therapy after liver transplantation. METHODS: We performed a retrospective analysis of 170 allograft liver biopsy specimens from 36 patients who received a liver transplant for chronic HCV infection, had recurrent HCV infection after transplantation, and subsequently achieved SVR (collected from 1999 through 2015 at 4 medical centers). SVR was defined as an undetectable serum HCV RNA level 24 weeks after completion of HCV treatment. A total of 65 biopsy specimens were post-SVR (at least 1 post-SVR from each patient; some biopsy specimens were collected at later time points from a subset of patients). We performed polymerase chain reaction analysis for HCV RNA on a subset of the biopsy specimens (28 collected before SVR and 32 after SVR). RESULTS: Of the 65 post-SVR biopsy specimens, 45 (69%) had histologic features of active HCV infection. Of the initial post-SVR biopsy specimens collected from each of the 36 patients, 32 (89%) showed these changes. For patients with more than 1 post-SVR biopsy specimen, 6 (46%) had no change in fibrosis between biopsies, and fibrosis worsened for 3 patients (23%) based on their most recent biopsy. The HCV RNA level was undetectable in 31 of the 32 biopsy specimens analyzed by polymerase chain reaction. CONCLUSIONS: In a retrospective analysis of allograft liver biopsy specimens from patients who achieved SVR after a liver transplant for chronic HCV infection, histologic changes associated with active HCV were present in 69% and fibrosis continued to progress in 23%, despite the lack of detection of HCV RNA. Pathologists should be aware of patients' SVR status when analyzing liver biopsy specimens to avoid diagnoses of chronic HCV-associated hepatitis. Because of the persistent inflammatory activity and fibrosis after SVR, clinicians should continue to monitor patients carefully after SVR to anti-HCV therapy.

Colorectal carcinomas with submucosal invasion (pT1): analysis of histopathological and molecular factors predicting lymph node metastasis.

Submucosally invasive colorectal carcinoma (pT1) has the potential to be cured by local excision. In US surgical intervention is reserved for tumors with high-grade morphology, lymphvascular invasion, and close/positive margin. In other countries, particularly Japan, surgical therapy is also recommended for mucinous tumors, tumors with >1000 µm of submucosal invasion, and those with high tumor budding. These histological features have not been well evaluated in a western cohort of pT1 carcinomas. In a cohort of 116 surgically resected pT1 colorectal carcinomas, high tumor budding (P<0.001), lymphatic invasion (P=0.003), depth of submucosal invasion >1000 µm (P=0.04), and high-grade morphology (P=0.04) were significantly associated with lymph node metastasis on univariate analysis. Mucinous differentiation, tumor location, tumor growth pattern, and size of invasive component were not significant. On multivariate analysis, only high tumor budding was associated with lymph node metastasis with an odds ratio of 4.3 (P=0.004). A subset of 48 tumors (22 node-positive and 26 node-negative) was analyzed for mutations in 50 oncogenes and tumor suppressors. No statistically significant molecular alterations in these 50 genes were associated with lymph node status. However, lymphatic invasion was associated with BRAF mutations (P=0.01). Furthermore, high tumor budding was associated with mutations in TP53 (P=0.03) and inversely associated with mutations in the mTOR pathway (PIK3CA and AKT, P=0.02). In conclusion, this study demonstrates the importance of identifying high tumor budding in pT1 carcinomas when considering additional surgical resection. Molecular alterations associated with adverse histological features are identified.

Upper tract urothelial carcinomas: frequency of association with mismatch repair protein loss and lynch syndrome.

Increased risk for upper tract urothelial carcinoma is described in patients with Lynch syndrome, caused by germline mutations in mismatch repair genes. We aimed to identify the frequency of mismatch repair protein loss in upper tract urothelial carcinoma and its potential for identifying an association with Lynch syndrome. We queried our database to identify upper tract urothelial carcinomas. Patients were cross-referenced for history of colorectal carcinoma or other common Lynch syndrome-associated neoplasms to enrich for potential Lynch syndrome cases. Tumor histopathologic characteristics were reviewed and each case was analyzed for loss of mismatch repair proteins, MLH1, MSH2, MSH6, and PMS2, by immunohistochemistry. Of 444 patients with upper tract urothelial carcinoma, a subset of 215 (encompassing 30 with upper tract urothelial carcinoma and another common Lynch syndrome-associated neoplasm) was analyzed for loss of mismatch repair protein expression. Of 30 patients with Lynch syndrome-associated neoplasms, six had documented Lynch syndrome, including two with Muir-Torre syndrome. Mismatch repair protein loss was identified in 7% of total upper tract urothelial carcinomas and 30% of patients with Lynch syndrome-associated neoplasms (including all patients with Lynch syndrome/Muir-Torre syndrome). Of patients without history of Lynch syndrome-associated neoplasms, 5 of 184 (2.7%) had loss of mismatch repair protein expression. Twelve cases with mismatch repair protein loss demonstrated loss of MSH2 and MSH6, and 2 had isolated loss of MSH6. MLH1 and PMS2 expression were consistently retained. Although increased intratumoral lymphocytes, inverted growth, pushing tumor-stromal interface, and lack of nuclear pleomorphism were more commonly seen in cases with mismatch repair protein loss, only intratumoral lymphocytes and presence of pushing borders were statistically significant. MLH1 and PMS2 testing appear to have little utility in upper tract urothelial carcinoma; however, mismatch repair protein loss of MSH2 and/or MSH6 by immunohistochemistry seems relatively sensitive and specific for identifying patients with potential Lynch syndrome.

Amyloid Pseudo-Dacryolith and Nasolacrimal Obstruction in a 67-Year-Old Male.

A 67-year-old male with a 35-year history of left-sided epiphora presented with a nonpainful, noninflamed, left medial canthal mass and complete left nasolacrimal obstruction. During routine dacryocystorhinostomy, a lesion was present within the lacrimal sac that mimicked a lacrimal stone in appearance but with a consistency concerning for malignancy. Histologically, the lesion displayed apple-green birefringence on polarized light microscopy and Congo red staining. The patient was referred to the hematology service for evaluation, which failed to reveal systemic disease. There is 1 previous report of localized amyloidosis to the nasolacrimal excretory system in which the lesion was invasive and caused bony erosion. The authors present a second case of localized, nasolacrimal amyloidosis mimicking both neoplasm and dacryolith without bony erosion.

Langerhans cell collections, but not eosinophils, are clues to a diagnosis of allergic contact dermatitis in appropriate skin biopsies.

BACKGROUND: Langerhans cell collections (LCCs) and eosinophils are traditionally considered histologic clues to allergic contact dermatitis (ACD), but rigorous histologic analyses are limited. We correlated the presence of LCCs and eosinophils in skin biopsies with patch test results in patients evaluated for ACD. METHODS: Charts of all patients patch tested and biopsied at one institution from 2011 to 2013 were reviewed. Biopsies had to have a diagnosis of either spongiotic dermatitis, psoriasiform dermatitis or mixed psoriasiform/spongiotic dermatitis. Various histologic parameters were assessed, including the presence of LCCs and number of eosinophils. DESIGN: A total of 68 biopsies met study criteria. Of these, 27 (40%) had ≥1 LCC. Twenty-one out of 27 (78%) with ≥1 LCC were patch test positive; 6 were patch test negative (22%). Of 41 cases with no LCCs, 23 were patch test positive (23/41, 56%) and 18 were patch test negative (18/41, 44%). LCCs were significantly more common in patch test positive patients (p = 0.046). Eosinophil count did not significantly differ in patch test positive and negative cases (p = 0.216). CONCLUSION: LCCs are significantly more common in patch test positive cases. There were no differences with regards to presence of eosinophils between patch test positive and negative groups.

Serrated Polyps and Serrated Polyposis Syndrome.

Colorectal serrated polyps are intermediate lesions in the serrated neoplastic pathway, which account for up to 30% of colorectal cancers. This pathway is biologically distinct from the adenoma-to-carcinoma sequence, with associated cancers exhibiting mutations in the BRAF oncogene, DNA promoter hypermethylation, and microsatellite instability. An evolving understanding of these unique lesions has led to the development of a more accurate classification, improved endoscopic identification, and tailored clinical management guidelines. This article reviews serrated polyps and serrated polyposis syndrome.

Risk for esophageal neoplasia in Barrett's esophagus patients with mucosal changes indefinite for dysplasia.

BACKGROUND AND AIM: Patients with Barrett's esophagus (BE) are at increased risk for esophageal adenocarcinoma (EAC) and therefore require surveillance. Biopsies are classified as indefinite for dysplasia (IND) when the significance of epithelial abnormalities is uncertain due to inflammation or sampling. Our aim was to characterize the neoplastic risk of IND in BE patients and to identify predictors of neoplastic risk. METHODS: Our pathology database from 1992 to 2007 was searched for BE and IND. Progression rates were calculated and univariate analysis was performed to identify predictors for neoplasia progression in BE-IND patients. RESULTS: Among 85 patients who had a follow-up (FU) biopsy within 1 year, 11 (12.9%) patients had prevalent neoplasia (seven low-grade dysplasia [LGD], two high-grade dysplasia [HGD], and two EAC). Among 82 patients who did not have prevalent neoplasia but had ≥ 1 year FU, 17 progressed to dysplasia (14 LGD, 3 HGD) and 2 developed EAC during a mean FU period of 59 months. The incidence of neoplasia (LGD, HGD, or EAC) and advanced neoplasia (HGD + EAC) was 4.5 and 1.2 cases per 100 patient-years, respectively. Longer length of BE and multi-focal IND on index biopsy were associated with progression to neoplasia. CONCLUSION: Patients with BE-IND carry a significant risk of harboring prevalent dysplasia, but the risk of incident dysplasia is similar to the general BE population. The length of BE and the multifocal IND might tentatively help to identify a patient subpopulation at higher risk of neoplastic progression before more definitive data becomes available.

Sarcoid-like reaction in sentinel lymph node draining conjunctival melanoma.

A sarcoid-like reaction is the presence of noncaseating granulomas due to a T-cell mediated inflammatory reaction in draining lymph nodes of tumors or in the vicinity of tumors. Breast cancer, lymphoma, and cutaneous melanoma have been observed to induce a sarcoid-like reaction. Herein, a patient is reported with conjunctival melanoma in whom multiple noncaseating granulomas were observed in the sentinel lymph node without evidence of micrometastasis. Fungal and mycobacterium stainings were negative and further systemic workup excluded sarcoidosis. This case identifies conjunctival melanoma as a cause of a sarcoid-like reaction.

Anatomy and histology of the frontalis muscle.

PURPOSE: To determine the gross and histologic configurations of the medial and lateral frontalis muscle. METHODS: After making a midcoronal incision and bluntly dissecting to the orbital rim, the frontalis muscle was marked and measured. A protractor was used to measure the frontalis-orbicularis angle (FOA) and, when present, the angle of central bifurcation (AOB). Three strips of full-thickness forehead soft tissue measuring 0.5 cm × 8 cm were excised 3, 4.5, and 6 cm above the supraorbital notch and analyzed histologically for the presence of skeletal muscle fibers. Data were analyzed using 2-sample t tests, paired t tests, Pearson correlations, and mixed effect models. A p value of ≤ 0.05 was considered statistically significant. RESULTS: Sixty-four hemifaces of 32 cadavers (16 males) were dissected. All specimens were Caucasian. The average age was 78.2 years (range, 56-102 years). The average FOA was 88.7° (13.0°), and the average AOB was 90.0° (26.4°). A visible midline bifurcation occurred in 28 of 32 subjects (88%) at an average height of 4.7 cm (range, 2.4-7.2 cm) superior to the supraorbital notch. Continuous skeletal muscle fibers were present within the midline bifurcation histologically in 89%, 75%, and 11% of specimens 3.5, 5.0, and 6.5 cm above the supraorbital notch, respectively. In 46% of individuals, skeletal muscle fibers were continuously present microscopically within the gross bifurcation. CONCLUSION: While a medial frontalis muscle bifurcation occurs grossly in most senescent Caucasians, muscle fibers exist microscopically within this zone in nearly half of individuals.

Microanatomical Location of Hyaluronic Acid Gel Following Injection of the Temporal Hollows.

PURPOSE: To examine the microanatomical location of hyaluronic acid gel injected within the temporal hollows of cadaver specimens. METHODS: The temporal hollows were injected subcutaneously with hyaluronic acid gel in 6 fresh frozen human cadaver hemifaces. Temporal soft tissues were dissected to a preperiosteal plane and fixated in 95% alcohol. A soft tissue section extending from skin to temporal bone was obtained for each specimen. Histologic examination was performed using hematoxylin and eosin stain. RESULTS: In 5 of 6 specimens, at least 95% of the hyaluronic acid was located within the subcutaneous fat. In 1 of 6 specimens, approximately 35% of the material was located within the subcutaneous fat and 60% was located within the superficial temporal fascia. Two specimens had 5% located within the temporalis muscle. In 1 specimen, hyaluronic acid was found to encompass a superficial muscular artery within the superficial temporal fascia. CONCLUSIONS: This study elucidates the location of hyaluronic acid gel after subcutaneous injection within the temporal hollow. Histology confirmed consistent placement of the gel within the subcutaneous tissues, but it also showed that injection in this region may produce unintended deeper location of filler, and a significant perivascular collection of the material. The proximity of dense temporal fascial and muscle arterial networks in this region may pose risk for perivascular injection and associated complications.

Regional Variations in Orbicularis Oculi Histology.

PURPOSE: To investigate and compare the histologic compositions of the pretarsal, preseptal, and orbital orbicularis oculi muscle (OOM) using nonpreserved, fresh-frozen, human cadavers. METHODS: The OOM was exposed using sharp and blunt dissection. A metric ruler was used to measure and mark 0.5 cm × 1 cm samples from each portion of the right, superior OOM. Samples were excised, fixed in formalin, and completely embedded in paraffin. Five-micrometer-thick, hematoxylin- and eosin-stained sections were generated for each sample and analyzed by an anatomical pathologist. The relative percentages of the 4 main tissue types (skeletal muscle, fibrous tissue, adipose tissue, and neurovascular tissue) were quantified. RESULTS: Forty-two samples were obtained from 14 Caucasian cadavers. On average, the pretarsal samples were composed of 83.5% skeletal muscle, 0.0% adipose, 5.0% neurovascular, and 11.5% fibrous tissue. Average preseptal OOM was 46.5% skeletal muscle, 12.7% adipose, 9.2% neurovascular, and 31.5% fibrous tissue. The orbital OOM was, on average, 42.7% skeletal muscle, 32.7% adipose tissue, 6.9% neurovascular, and 17.7% fibrous tissue. CONCLUSIONS: The OOM represents a histologically heterogeneous structure.