Cystic neck swellings constitute a diverse group of congenital, inflammatory, and neoplastic lesions, presenting a diagnostic challenge due to overlapping clinical and radiological features. In adults, particularly in elderly patients, lateral neck cysts raise immediate concern for cystic metastases from head and neck squamous cell carcinoma, followed by congenital lesions such as second branchial cleft cysts, cystic lymph nodes, neurogenic tumors, and dermoid cysts. Branchial cleft cysts, although common in cutaneous locations, are distinctly uncommon in the deep cervical compartments and are rarely considered in the initial differential diagnosis. The occurrence in deeper neck spaces such as the carotid triangle is extremely rare and often leads clinicians to favor congenital cysts or neoplastic lesions over benign epidermoid pathology. Imaging modalities such as ultrasound and contrast-enhanced CT provide essential information regarding lesion morphology and anatomical relationships; however, they may not reliably differentiate BCC from congenital or metastatic cystic masses. Fine-needle aspiration cytology (FNAC), demonstrating keratinous debris and anucleated squamous cells, remains invaluable for diagnosis, yet cytology findings alone must be correlated with clinical and radiological context. Given the rarity of deep cervical BCC and the potential for misdiagnosis, especially in older adults, reporting such cases is important to enhance clinical awareness. This case highlights the diagnostic complexities of an EIC presenting in the carotid space of a 72-year-old male, initially mimicking a branchial cleft cyst, and underscores the role of a multimodal diagnostic strategy and definitive surgical excision.

A 72-year-old male presented to the surgical outpatient department with swelling on the right side of the neck for the past 3-4 months. The swelling was initially asymptomatic, gradually increased in size, and later became mildly tender on palpation. There was no history of fever, discharge, dysphagia, odynophagia, hoarseness of voice, trauma, prior surgery, or weight loss. On examination, a 3 × 1 cm soft, fluctuant, non-pulsatile swelling was identified in the right Level III cervical region, situated deep to the sternocleidomastoid muscle. The mass was non-transilluminant, had smooth margins, and displayed no overlying skin changes. There was no clinically palpable lymphadenopathy. General examination revealed a moderately built individual with pallor, but no pedal edema, icterus, or generalized lymphadenopathy. Vital signs were stable except for tachycardia (pulse 120 bpm), and systemic examination was unremarkable. Contrast-enhanced CT (CECT) of the neck demonstrated a well-defined, hypodense, non-enhancing cystic lesion measuring 2.4 × 2.3 × 1.9 cm within the right carotid space, compressing the internal jugular vein (IJV) and abutting the common carotid artery. Fat planes were preserved, and no evidence of vascular invasion or thrombosis was seen. Ultrasound showed a heterogeneously hypoechoic avascular lesion without significant regional lymphadenopathy. Based on imaging, differential diagnoses considered included a second branchial cleft cyst, a cystic lymph node, or a nerve sheath tumor. FNAC was performed twice, yielding pultaceous, greasy material. Cytology revealed abundant anucleated squames, keratin debris, and a few nucleated squamous cells, without granulomatous inflammation or atypia. These findings were consistent with an Branchial cleft cyst, although initially misinterpreted as a branchial cleft cyst due to the unusual deep cervical location. Figure 1: Preoperative image showing a visible swelling in the right lateral aspect of the neck. The mass appears smooth, well-defined, and located deep to the sternocleidomastoid muscle Figure 2: Lateral view of the neck demonstrating the prominent swelling prior to surgical intervention. The lesion is well-circumscribed, smooth, and located in the right carotid space Preoperative evaluation revealed anemia (Hb 8.0 g/dL) and Mallampati Grade III/IV, but other labs, ECG, and chest X-ray were within normal limits. After appropriate counseling and consent, the patient underwent surgical excision of the cyst under general anesthesia. A horizontal incision was made along the neck skin crease; the cyst was dissected from surrounding structures and removed in toto without rupture. Hemostasis was secured, and the wound was closed in layers. Postoperative recovery was uneventful, with no signs of recurrence or complications. The case highlights the importance of a multidisciplinary approach using clinical examination, imaging, cytology, and surgical intervention to accurately diagnose and manage Branchial cleft cysts in the lateral neck, especially when the presentation mimics more common entities like branchial cleft cysts. Figure 3: Intraoperative image showing a well-encapsulated, globular, cystic mass located in the right cervical region deep to the platysma and sternocleidomastoid muscle. The lesion was identified and dissected free from surrounding structures Figure 4: Intraoperative photograph demonstrating careful dissection and mobilization of the cystic mass from surrounding soft tissues using blunt and sharp dissection techniques Figure 5: Rare Cyst (BCC) in Rt. Carotid triangle Excised without injuring cyst wall or internal jugular vein

Branchial cleft cysts are benign, slow-growing cystic lesions arising from the proliferation of epidermal elements within the dermis. While they are relatively common on the scalp, face, trunk, and extremities, their occurrence in the deep cervical spaces is exceedingly rare. This unusual anatomical location often leads to diagnostic confusion, particularly in elderly individuals, where cystic neck masses are more commonly evaluated for metastatic disease or congenital anomalies such as second branchial cleft cysts. The present case exemplifies this diagnostic dilemma, as the deep location and clinical features initially favored a diagnosis of a branchial cleft cyst, even though cytology ultimately confirmed an EIC. The patient, a 72-year-old male, presented with a progressively enlarging, painless swelling deep to the sternocleidomastoid muscle—an area classically associated with second branchial cleft cysts. Such anatomical overlap frequently contributes to misclassification of BCC in the neck, as noted in prior reports where atypical BCC mimicked congenital cysts or cystic lymph nodes. In elderly patients, the differential must also include cystic metastases from head and neck squamous cell carcinoma, which often present similarly and may share overlapping cytological features. Therefore, in this age group, clinicians must exercise heightened vigilance to avoid underdiagnosing potentially malignant lesions. Imaging in this case played a pivotal role but also contributed to the complexity. Contrast-enhanced CT revealed a well-defined, non-enhancing cystic lesion compressing the internal jugular vein—features compatible with both benign congenital cysts and BCC. The absence of internal vascularity on ultrasound favored a benign etiology, but imaging alone could not definitively rule out branchial cleft cysts or cystic lymphadenopathy. Comparable instances have been documented in the literature, where BCC located in deep cervical compartments were indistinguishable from branchial anomalies until after surgical excision and histopathological confirmation. Fine-needle aspiration cytology (FNAC) provided the crucial diagnostic clue in this case. The presence of abundant keratinous debris, anucleated squames, and occasional nucleated squamous cells is characteristic of Branchial cleft cysts. FNAC is typically reliable for diagnosing BCC; however, in rare situations—particularly in cystic metastases with keratinization—cytologic overlap may occur. Therefore, correlation with clinical and radiological findings is essential, especially in older adults. Surgical excision remains the gold standard for definitive treatment of BCC. Complete removal of the cyst and its capsule is necessary to prevent recurrence and allows histopathological confirmation. In this case, the cyst was excised intact despite its deep location near major neurovascular structures. The uneventful recovery and absence of recurrence underscore the effectiveness of complete surgical excision in managing deep cervical BCC. Although BCC are benign and typically occur in younger or middle-aged patients, rare cases have been documented in the elderly, including individuals over 90 years old. Such presentations highlight the need to maintain a broad differential diagnosis for lateral neck cysts across all age groups. The present case contributes to the limited literature describing deep cervical BCC in elderly patients and emphasizes the importance of a multimodal diagnostic strategy integrating clinical evaluation, imaging, FNAC, and surgical excision. This case reinforces that Branchial cleft cysts, though uncommon in the lateral neck and particularly in deep spaces such as the carotid triangle, must be considered in the differential diagnosis to avoid misinterpretation as branchial cleft cysts or metastatic cystic lesions. Accurate identification is essential to ensure appropriate management, avoid unnecessary oncologic evaluation, and deliver optimal patient outcomes.

Branchial cleft cysts arising in the deep cervical spaces are uncommon and can closely mimic congenital cysts such as second branchial cleft cysts or even cystic metastatic deposits, especially in elderly patients. This case illustrates the diagnostic challenges posed by such atypical presentations and highlights the importance of integrating clinical evaluation, imaging studies, and cytology to achieve diagnostic clarity. FNAC remains a valuable tool in identifying characteristic keratinous debris and squamous elements, but correlation with imaging findings is essential to avoid misinterpretation. Surgical excision continues to be the definitive treatment for BCC, offering both therapeutic relief and histopathological confirmation. The absence of recurrence following complete excision in this case supports the effectiveness of this approach. Clinicians should maintain a broad differential diagnosis for lateral neck cysts across all age groups and consider BCC even in deep, unusual locations to prevent unnecessary oncologic investigations and ensure timely, appropriate management. FUTURE DIRECTIONS Although Branchial cleft cysts are benign and generally curable with complete excision, several areas warrant further exploration. First, larger clinical studies or multicenter registries documenting deep cervical BCC are needed to elucidate their natural history, recurrence potential, and rare malignant transformation risk. Second, development of standardized imaging criteria distinguishing BCC from other cystic neck lesions particularly branchial cleft cysts and cystic metastases would greatly enhance diagnostic accuracy. Advanced modalities such as diffusion-weighted MRI may help identify keratinous content preoperatively. Furthermore, identifying molecular or histopathological markers capable of differentiating simple BCC from atypical or malignant cysts would improve clinical decision-making. Finally, increasing awareness among clinicians regarding the atypical presentations of BCC especially in elderly patients may reduce misdiagnosis, prevent unnecessary anxiety or invasive workups, and promote timely, appropriate management.

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