CASE REPORTS Primary branchiogenic carcinoma – is it a valid entity?

Branchial cyst is due to a congenital defect that occurs early in embryonic development. It is the most common congenital cause of a neck mass which results from a failure of obliteration of one of the branchial clefts during embryonic development. No ethnic or sexual predilection has been reported. Approximately 2-3% of cases are bilateral. A tendency for familial clustering has been documented [1]. Branchial cysts may not present clinically until early adulthood. They may become enlarged and tender especially following an upper respiratory tract infection. Sudden rupture of an abscess which has developed inside a branchial cyst may lead to the formation of a discharging sinus. Depending on the size of the branchial cyst local symptoms such as dysphagia, dysphonia or dyspnoea may occur [2]. We present a case report wherein the patient underwent excision of a branchial cyst on the right side of the neck which revealed squamous cell carcinoma in its lining.


Introduction
Branchial cyst is due to a congenital defect that occurs early in embryonic development. It is the most common congenital cause of a neck mass which results from a failure of obliteration of one of the branchial clefts during embryonic development. No ethnic or sexual predilection has been reported. Approximately 2-3% of cases are bilateral. A tendency for familial clustering has been documented [1].
Branchial cysts may not present clinically until early adulthood. They may become enlarged and tender especially following an upper respiratory tract infection. Sudden rupture of an abscess which has developed inside a branchial cyst may lead to the formation of a discharging sinus.
Depending on the size of the branchial cyst local symptoms such as dysphagia, dysphonia or dyspnoea may occur [2].
We present a case report wherein the patient underwent excision of a branchial cyst on the right side of the neck which revealed squamous cell carcinoma in its lining.

Case Report
A 35-year old male, non-smoker, presented to us with a fluctuant, non-tender lump. The lump was on the right side of the upper third of the neck in the anterior triangle and had been present for 4 months duration. Computerized tomography (CT) showed a well-defined cystic mass of 46 x 24 x 22 mm, which was anterolateral to the carotid sheath. There were no tracts connected to the cyst and no evidence of lymphadenopathy or any other malignancies of the head and neck region either clinically or radiologically. The preliminary diagnosis was a branchial cyst and the patient was referred for fine needle aspiration cytology.

Cytological findings:
Approximately 1.5 ml of a brown coloured thin fluid was obtained by fine needle aspiration. Smears revealed sheets of squamous epithelial cells mixed with a large number of mature lymphocytes, neutrophils and macrophages. The epithelial cell component exhibited nuclear atypia and the smears were categorized as "C3/atypical cells" according to the WHO guidelines [ Figure 1].

Morphological findings:
In view of the atypical cytological findings the lesion was excised in toto. Gross examination showed a thin walled collapsed cyst measuring 3.5 x 2.5 x 2 cm [ Figure 2] with a solid whitish (12 x 10mm) mural nodule.    Figure 3]. There was an area of transition from a benign epithelium to full thickness dysplasia [ Figure 4 and 5] and invasive carcinoma. Pancytokeratin stain highlighted the invasive area of the cyst wall [ Figure 6].

Discussion
Occurrence of primary carcinoma in a branchial cyst has been considered controversial. Khafif  Bhanote [3] identified 14 cases between 1982 and 2008 that passed the Khafif criteria [1]. There were 6 reports totalling 9 cases of primary branchial cyst carcinoma between 2008 and 2014. These reports were by Roche (2010), Banikas (2011), Veivers (2012), Chauhan (2013), Tegeltija (2013) and Anantharajan (2014) [4 -7]. Banikas [5] and others believe that true primary carcinomas occur, citing the simultaneous presence of in situ carcinoma, early invasion and invasive carcinoma. In spite of the above reports scepticism about this entity persists. Veivers and Dent have shown that current investigative methods are unsatisfactory in the diagnosis of hidden primaries. Therefore, item 5 of the Khafif criteria is difficult to be satisfied. Surgeons would be encouraged by the findings of Veivers and Dent to complete the diagnostic work up to minimize errors.

Conclusion
Primary branchiogenic carcinoma is a controversial clinicopathological entity with conflicting results in literature. However, we believe our case satisfies all the diagnostic criteria described by Khafif et al [1]. The most important criterion emphasized by the author of demonstrating the zone of transition from benign to full thickness dysplasia and frankly invasive carcinoma, was    clearly identified in our case. Hence we report this case as a primary squamous cell carcinoma (early invasive) arising in a branchial cyst. Since the lesion was completely excised no further surgery was attempted. Patient has been regularly followed-up for the last 3 years. There is no evidence of recurrence or metastasis or the emergence of an occult primary to date. All above findings lend credence to the fact that it is indeed a primary branchiogenic carcinoma.