Nasal Sesamoid Cartilages: Fact or Fiction? An Anatomical Study of the Lateral Nasal Ala

Introduction

The cartilaginous anatomy of the nasal exterior has been long-established to primarily include the upper (ULC) and lower (LLC) lateral cartilages. These cartilages provide structural support and are chiefly composed of hyaline cartilage. Anatomical atlases and texts commonly include the accessory and sesamoid cartilages and sesamoid accessory cartilages when describing the composition of the LNA (Figure 1). ¹ Accessory cartilages are defined as small nasal cartilages between the lateral crus and piriform aperture of the nose bilaterally. ² Sesamoid cartilages are defined as bilateral small nasal cartilage(s) between the upper lateral nasal cartilage and piriform aperture. ²

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Figure 1.

Classical anatomical rendering of the cartilaginous structure of the nose including depictions of the sesamoid and accessory cartilages. ³

Previous studies have explored anatomical variations in the lateral nose in various populations. Ebrahimi et al assessed the accessory cartilages in 41 Iranian cadavers. They found that 5 (12%) had no sesamoid cartilage while 36 (88%) had a single sesamoid cartilage on each side. When the sesamoids were absent, the authors instead found “fibrous tissue between the tail of the lateral crus and piriform aperture^”. ² In their study of 10 Asian cadaveric noses, Han et al found sesamoid cartilage to be present in their specimens. ⁴

Despite this dogma, the authors debate the presence of sesamoid and accessory cartilages, as they have not been observed macroscopically or microscopically in their nasal surgical practices. Previous studies found significant differences in the cartilaginous anatomy of the nasal tip.^2,5 We postulate that a similar degree of variability may exist within the LNA. Studies have analyzed the support structure of the nasal tip, but few have attempted to fully characterize the composition of the LNA. ⁵ For example, Dowlatshahi et al found that skeletal muscle provided primary support structure of the LNA but made no mention of sesamoid or accessory cartilages in their cadaveric study. ⁶ Further, Daniel et al grossly identified accessory cartilage chains in 20 Caucasian cadavers, but did not visualize sesamoid cartilages. ⁷

This study aims to clarify the anatomy of the LNA and relate it to the structural support of the lower nose by analyzing histologic specimens from the LNA soft tissues in patients undergoing Mohs micrographic surgical excision of cutaneous malignancies. Specifically, the presence of sesamoid and accessory cartilages in this region will be examined. It is hypothesized that these cartilages are oftentimes absent. In their stead, a dense network of fibrous/fatty tissue provides structural support. Additionally, this histological review will permit an updated, detailed characterization of the specific soft tissues present in the LNA. This clarification may inform future medical decision making when reconstructing the form and function of the LNA.

Materials and Methods

A retrospective histological review of cutaneous and subcutaneous tissues collected from the LNA of 101 Mohs surgical cases was conducted. This study was approved by our Institutional Review Board under study A21-118. Cases were identified in the electronic medical record using ICD-10 codes C44.311 (basal cell carcinoma of the nose) and C44.321 (squamous cell carcinoma of the nose). All study specimens were previously collected during Mohs micrographic surgical excision of nonmelanoma cutaneous malignancy. One hundred one cases met the inclusion criterion requiring resection of a significant amount of the LNA. Patients with insufficient degrees of tissue excision to adequately characterize the anatomical makeup of the LNA were excluded. The medial border of the area of study was defined as the lateral edge of the lateral crus of the LLC. The lateral border corresponded to the alar-facial sulcus. The superior border was the supra-alar crease, and the inferior border was represented by the alar rim. Previously resected specimens were stained with H&E and microscopically reviewed by a board-certified Mohs surgeon (a study author) to characterize all tissue elements populating the region of study. Representative cases were photographed and included for illustrative purposes.

Results

The 101 cases reviewed included greater than 1000 histologic tissue sections from 362 tissue blocks. Demographics are shown in Table 1. Epidermal and dermal layers of the skin were identified in all specimens. All specimens included dermal appendageal structures, including hair follicles and glandular elements. Some also contained residual invasive basal cell carcinoma or squamous cell carcinoma.

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Table 1.

Demographic Information of 101 Included Patients and Type of Tumor Resected From Lateral Nasal ala.

Patient characteristics
Age (mean)	70
Min	34
Max	93
Sex
Male	51
Female	50
Race
Caucasian	101
Tumor type
Basal cell carcinoma	89
Squamous cell carcinoma	10
Sebaceous carcinoma	2

Within the subcutaneous tissues, specimens exhibited a variable amount of adipose tissue ranging from sparse to abundant. Striated skeletal muscle, composed of long multinucleated fibers, closely approximated the adipose elements. Adipose tissue was located either superficial to the skeletal muscle layer or admixed within muscle and fibrous tissue. The muscle itself manifested a more superficial component that extended into the reticular dermis and a deeper component within a surrounding network of loose, fibrous connective tissue. This deeper muscular component extended almost to the level of the mucosa. The depths of resection for each case are shown in Table 2; the majority (67) extended through adipose tissue, skeletal muscle, and fibrous tissue. Representative images are included in Figures 2 and 3. A demonstrative image of an alar resection is included in Figure 4.

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Table 2.

Number of Patients With Each Level of Depth of Resection Present on Histological Analysis With H&E Stain.

Depth of resection	Number of patients
Skin depth resected	101
Adipose tissue depth resected	87
Skeletal muscle depth resected	90
Fibrous tissue depth resected	69
Nasal mucosa depth resected	1

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Figure 2.

Histological sample at 2× magnification showing the epidermis, dermis, subcutaneous fat, muscle, and deep fibrous tissue. Representative of 100/101 samples examined. No cartilaginous components are present.

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Figure 3.

Representative histological sample of 100/101 samples at 10× magnification showing a close-up view of the skeletal muscle and nerves within the fibrous stroma. Notably, no cartilage is present.

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Figure 4.

Representative nasal alar case to demonstrate location of areas of resection.

Of the 101 cases reviewed, only one had cartilage present. Cartilage was identified by its glassy, basophilic appearance with an abundant array of fine collagen fibers, as pictured in Figure 5. This specimen involved a large, deep resection extending through and through the mucosa of the lateral nasal vestibule; the cartilage in this full-thickness resection was interpreted to represent a portion of the lateral crus of the LLC based on the specific tumor location.

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Figure 5.

Histological image of the sole sample containing cartilaginous components at 10× magnification.

Discussion

An accurate understanding of nasal anatomy is important to all students of facial anatomy. Variations in nasal anatomy influence both form and function during esthetic and reconstructive surgery. The LLCs provide critical support for the nasal tip and nostrils at the level of the external nasal valves. This study sought to determine the prevalence and significance of the nasal sesamoid and accessory cartilages, as a structural, supportive function is historically ascribed to these structures in the lower nose.

The 101 cases histologically analyzed in this study revealed that the lateral nasal alar subcutaneous soft tissues were comprised of adipose tissue, skeletal muscle, and fibrous connective tissue (Table 2). Sixty-seven of the specimens extended to the depth of the fibrous tissue. While the amount of adipose tissue varied, the vast majority (90) contained skeletal muscle. Muscle was located in approximation to the adipose tissue and the adipose tissue was located in a variable position, either superficial to the muscle or admixed within muscle and underlying fibrous tissue. At its deepest level, skeletal muscle was found in close proximity to mucosa. The skeletal muscle represented the alar nasalis, transverse nasalis, and/or levator labii superioris alaeque nasi muscles. Together, these muscles contribute structural support to the nasal ala during respiration. ⁶

One-hundred of the 101 cases failed to demonstrate the presence of sesamoid or accessory cartilages in the traditionally described anatomical locations between the lateral crus and piriform aperture. The glassy, basophilic histologic appearance of collagen fibers, characteristic of cartilage, was entirely absent in 100 (99%) of study cases. Rather, this area was composed of dense fibrous tissue. The authors believe this dense network of fibrous connective tissue provides meaningful support for the LNA.

The complete absence of sesamoid cartilages in this study lies in stark contradistinction to the results of previous studies and classical anatomic renderings of the nasal ala.^2,4,7 However, based on the authors’ surgical experience characterized by the collective and utter inability to grossly identify sesamoid and accessory cartilages, this result was not entirely unexpected. This is the first study specifically seeking to explore the presence of sesamoid cartilages in a United States population, as well as one of the first analyses of specimens obtained from living tissue. Although Daniel et al believe they grossly identified accessory cartilage chains in their cadaveric specimens, they did not complete a histological study, nor did they demonstrate the presence of any sesamoid cartilages. ⁷ The contrasting results point to the distinct possibility that the lateral nasal alar anatomy is more variable than classical teachings dictate. In an assessment of 8 cadaveric specimens, Haddad et al found no evidence of sesamoid cartilages utilizing a micro-MRI approach, correlating with the present study, however, they did visualize posterior accessory cartilage in 75% of subjects. ⁸ Further, Rohrich et al completed a cadaveric study of 10 subjects seeking to define this anatomic area, noting a fascial complex encompassing the area between the upper and lower lateral cartilage, similar to the dense fibrous tissue visualized in this study. This variability should be further investigated, introduced into nasal anatomical renderings and incorporated into educational pursuits.

Although it is unlikely that age, sex, race, or underlying medical issues significantly impacted the histologic appearance of the studied tissues, the lack of demographic diversity within our cohort is a limitation. Additionally, as these cases were obtained during the resection of cutaneous malignancy, it is theoretically possible (though unlikely) for the disease process to have eroded the cartilaginous structures prior to Mohs surgery. Further limitations of this study pertain to its relatively small sample size and the possibility that the failure to analyze full-thickness soft tissue specimens compromised the ability to detect the presence of cartilage.^2,4,7 It is also possible that dissection of soft tissues in the LNA could have reduced the inclusion of cartilage in the specimens. Additionally, as the initial excision of these specimens was not aimed at characterizing sesamoid and accessory cartilages, it is possible that the region may not have included these cartilages and that sampling error could reduce the accuracy of these results. Thus, the data collected, results, and conclusions must be interpreted within the context of these limitations. Future studies seeking to clarify the anatomical composition of the LNA should consider the analysis of full-thickness LNA soft tissue specimens.

Conclusion

Our retrospective histological study of 101 LNA cases revealed potential evidence of sesamoid or accessory cartilages in only a single specimen, implying that cartilage in this area may be quite rare. This finding provides insight to guide esthetic and reconstructive surgery involving the LNA. We hope to inspire further investigation into the true anatomic composition of this area of the nose.