Hamartomatous polyp of the palatine tonsil: histological considerations and review of the literature

Discussion

The head-and-neck anatomical region has a rich lymph drainage system and, thus, is a typical compartment for lymphangioma formation, usually in the subcutaneous tissues, parotid gland and tongue,.2 Lymphangiomatous polyps are common in the low gastrointestinal tract,.3 However, tonsillar lymphangiomatous polyps are rare entities with sparse reports in the literature,.1–19 Nevertheless, most authors agree that this condition has a higher incidence than reported because these masses can be overlooked in a routine examination and because of inconsistencies with their classification.1–6 Characteristically, a tonsillar lymphangioma may be reported in the literature under various terms like lymphangiomatous polyp, polypoid lymphangioma of the tonsil, lymphoid polyp, tonsillar angiofibroma, lymphangiectatic fibrolipomatous polyp, fibrolipoma, angiofibrolipoma, polypoid tumour containing fibroadipose tissue, hamartomatous tonsillar polyp and lymphangiectatic fibrous polyp.2 3 5 10 Notably, the last edition (5th) of the WHO classification of Head and Neck tumours uses the term ‘tonsillar hamartomatous polyp’ for a tonsillar lymphangiomatous polyp;20 thus, we comply with that terminology in our case report article.

Macroscopically, these lesions usually present as large, pale, smooth masses.1–3 5 10–13 Commonly, they are polypoid, but sessile lesions have also been described.1 10 The age of appearance varies, but it seems more common during the second decade of life,1–19 contrary to the typical lymphangiomas that are usually present at or around the time of birth.2 Most series do not show any sex or laterality predilection;1 10 however, a recent study supports a 1.4:1 male to female ratio.21 Reports of cases with bilateral tonsillar hamartomatous polyps are even rarer.14 15 Tonsillar hamartomatous polyps are not characterised by expansible growth or involution over time.2 15 Additionally, they are not associated with a higher incidence of the appearance of lymphatic malformations elsewhere in the body as part of a generalised process,3 15 and they are not accompanied by cervical lymphadenopathy.2 5 10 13 These lesions are usually asymptomatic, but some symptoms of varying degrees, like sore throat, dysphagia, snoring, foreign body sensation and chronic cough, have been reported.4 5 11 13 In a typical case of a hamartomatous polyp of the tonsil, an imaging examination would not offer any significant aid in the diagnosis. Thus, considering that it is also not easy to distinguish a malignant from a benign mass macroscopically, an excisional biopsy is always essential.

Several theories approach the pathophysiology of hamartomatous polyps’ formation. One theory supports that unsuccessful drainage of the lymphatic sacs to the veins leads to the dilation of isolated lymphatic channels.1–4 11 Another theory describes the abnormal isolation of lymphatic tissue during embryogenesis.1–4 11 Additional theories indicate abnormal development of lymphatics that lose their connection with their primordials and form lymph-filled cysts that penetrate the surrounding tissues along the lines of looser resistance.1–4 11 This abnormal proliferation may be attributed to the dysregulation of growth factors that participate in lymphangiogenesis, like VEGF-C and Prox-1, or reduced expression of angiogenesis inhibitors like thrombospondin-1,.2 4 10 14 Chronic inflammation in early bibliography was thought to be involved in the pathogenesis of tonsillar hamartomatous polyps via lymphatic channels’ obstruction and eventual oedema and mucosal prolapsed.2–4 10 13 16 However, this pathogenetic relation has not been established. On the one hand, chronic tonsillitis as a common condition does not usually appear with polypoid formation; on the other hand, the hamartomatous polyp does not necessarily occur in the context of chronic or recurrent tonsillitis. Probably the most common hypothesis supports the isolated hamartomatous traits of the tonsillar lymphangioma instead of a neoplastic character, based on a random proliferation of stromal elements normally found in the tonsil,.1 2 5 6 9–11 13 15–17

In most cases of tonsillar hamartomatous polyps, the procedure of choice is a bilateral tonsillectomy,.2 4 10 11 14–16 However, a simple lesion excision is probably sufficient with no recurrences reported in a 1-year follow-up,.3 7 These operations would not be expected to be more complicated than a typical tonsillectomy because the hamartomatous polyp is not invading the deep peritonsillar tissues. There is no reported recurrence or malignant transformation after complete excision. Other approaches like sclerotherapy or laser dissection have not shown more benefit than cold steel tonsillectomy, especially since the main concern is sending the lesion for a histological diagnosis to rule out malignancy,.4

The typical histological features of a tonsillar hamartomatous polyp include a non-keratinising stratified squamous epithelial covering, a core of loose fibrous and adipose tissue with sparse lymphoid aggregations and dilated thin-wall lymphatic and blood channels filled with lymph and lymphocytes, especially T-cells,.1–5 7–11 15 More rarely, these lesions appear as lymphoid papillary hyperplasia, which does not have prominent lymphoid follicles but more prominent lymphatic spaces.1 Additionally, unlike an exophytic squamous papilloma, a hamartomatous polyp does not show epithelial proliferation arranged in layers.1 10 A hamartomatous polyp is not expected to manifest any cytologic atypia or abnormal lymphatics infiltrating the deeper tissues of the tonsil.2 11 The different arrangement of normal tonsillar components may eventually classify the lymphangiomatous polyps as hamartomas instead of tumours.1 2 5–7 10–13 15–17 Immunohistochemical staining is unnecessary for the histological diagnosis; however, some studies have shown that most channels stained positive for Factor VIII-related antigen, anti-CD31 or anti-CD34.1 2 9

A hamartomatous polyp, a type of benign hamartomatous lesion, is a rare entity that may encounter the palatine tonsils. Despite its typical macroscopical appearance, performing an excisional biopsy for histological confirmation is always necessary. A typical tonsillectomy is the best therapeutical option with no expected specific complications or possibilities for recurrence.