Patient

A case report of a sclerotic fibroid of the oral mucosa

Sclerotic fibroma, also known as storiform collagenoma, is a rare benign tumor that grows on the skin, but it can also, less commonly, occur in the oral mucosa. It can present as part of the Cowden syndrome manifestation, especially when multiple lesions are encountered, but it can also occur as a solitary, sporadic lesion in healthy individuals. We describe a patient diagnosed with Cowden syndrome, who presented with a sclerotic fibroid in the oral mucosa, a highly unusual manifestation of Cowden syndrome.

Introduction

Sclerotic fibroma (SF), also called storiform collagenoma, is a rare benign tumor [1]. It presents as a cutaneous fibrous neoplasm [2]and it is especially uncommon in the mucosal tissue of the head and neck [1-2]. It arises from the proliferation of fibroblasts that show increased production of type I collagen [1]. SF affects both sexes, with a slight female predominance [2].

It presents as solitary or multiple skin nodules, which is an important marker in patients with Cowden syndrome (CS) [3-5]or as a sporadic, small, solitary mass of skin in healthy individuals [5].

First described in 1963 by Lloyd and Dennis [4]Cowden syndrome or multiple hamartoma syndrome [1]is a rare autosomal dominant hereditary genodermatosis [6]characterized by multiple hamartomas of ectodermal, mesodermal, and endodermal origin [4-6]. The phosphatase and tensin homolog (PTEN) gene negatively regulates cell proliferation and cell cycle progression [1].

CS is characterized by a large number of systemic abnormalities [1,3]Patients usually have macrocephaly, trichilemmomas and papillomatous papules/hamartomas [1]. CS is associated with a large number of PTEN hamartoma tumor syndrome (PHTS), a group of disorders characterized by the disorganized growth of native cells in native tissues [1]. CS is the only PHTS disorder associated with a well-reported predisposition to malignancies [1,4]; they are more likely to develop benign and malignant tumors of the mucous membranes and genitourinary and gastrointestinal tracts [1,3].

Mucocutaneous lesions are present in 99 to 100% of cases [5] and are pathognomonic [4]. The characteristic mucocutaneous findings include a variety of benign and malignant neoplasms (including SF) of the skin (facial, acral and palmar-plantar) [3]. Fibropithelial hyperplasia or diffuse papillomatosis are oral lesions commonly found in patients with Cowden syndrome [3,7]and often involve sites such as the tongue, gingiva, and lips [3,8]. On the contrary, SF is rarely identified in the same location [1,3,7].

The estimated prevalence of Cowden’s syndrome is 1/200,000 [4]. CS is usually diagnosed during the third decade of life (late 20s) [1,4].

There are very few reported cases of SF in the oral mucosa [1,3,5,6,9]. To our knowledge, only nine oral cavity SFs have been published in the medical literature.

The finding of multiple SFs should motivate further investigation due to the likelihood of a diagnosis of Cowden syndrome (chromosomal analysis for mutation in the putative PTEN gene) [1]and once the diagnosis is confirmed, further clinical and family history testing is recommended due to the reported increased risk of malignancies.

Case presentation

A 42-year-old man presented to the Stomatology Department with a known diagnosis of Cowden’s syndrome. A genetic study revealed an intronic mutation – thymine (T) to guanine (G) – T>G – transition at the +32 position of intron 8.

He has been followed by our Dermatology Department since 2012 for multiple hamartomas and trichilemmomas, mainly on the face and scalp (Figure 1).

Despite many appointments, the patient never showed up to perform the required colonoscopy, thyroid ultrasound, and genetic testing.

He presented to the Stomatology Department with an 11-month history of a slow-growing, painless mass on the dorsal surface of the tongue. The patient was referred with no history of trauma.

Clinical examination showed a pedunculated solid mass of approximately 2 cm on the dorsal surface of the tongue – lesion A (Figure 2). We also noted a white papillomatous lesion on the left commissure of the lips – lesion B (Figure: 3) – and a sessile lesion on the wet mucosa of the lower lip – lesion C (Figure 4).

A panoramic radiograph ruled out abnormalities and a clinical diagnosis of fibroepithelial hyperplasia was assumed.

Surgical excision was performed because of the small size of the lesions. Macroscopically they were well defined, firm and mucosal colored.

Histopathological examination showed that lesion A was characterized by a non-encapsulated proliferation of fibrous tissue in the Lamina Propria (Figure 5) consistent with sclerotic fibroma: a well-limited, hypocellular nodule composed of eosinophilic collagen bundles, arranged in a storiform or concentric lamellar pattern and separated by a prominent spectrum, along with sparse fibroblasts (Figure 6) with variable spindle or stellate morphology (Figure 7); lesion B was compatible with a hamartomatous lesion and lesion C with reactive fibroepithelial hyperplasia.

Discussion

A sclerotic fibroid is a rare benign soft tissue tumor that usually presents as a well-defined mass in the skin [1-2]. There are less than 100 case reports of SF in the world literature [10]. It is very uncommon for SF to manifest on the oral mucosa [3]but this kind of presentation has been published before [1]. SF can manifest as a sporadic, small, solitary mass of skin in otherwise healthy individuals [5] or as solitary or multiple skin nodules, an important marker in patients with Cowden syndrome (CS) [3-5].

Cowden syndrome is a genetic disorder characterized by a wide variety of symptoms and signs, including multiple skin/mucocutaneous lesions and involvement of several organs [4]. The organ system most consistently manifesting this syndrome is the skin [5]. In contrast to our male patient, there is a slight female predominance of CS [2].

According to the literature consulted, and as reported in this case, oral lesions such as fibroepithelial hyperplasia and hamartomatous or diffuse papillomatosis (lesions B and C) are commonly found in patients with Cowden syndrome. We thought it worthwhile to report the finding of an oral sclerotic fibroma (lesion A).

Although the histomorphology is usually representative, the neoplastic SF cells usually stain for vimentin and stain positive for CD34 in about 60% of the cases. [1,3]. In this case, the tumor cells strongly expressed vimentin, but were negative for CD34.

There are a few fibrous lesions that should be included in the histological differential diagnosis of tumors in the oral cavity [1,4] such as solitary fibrous tumor, traumatic fibroma, giant cell fibroma, and benign fibrous histiocytoma [8]. The fibroblasts of traumatic fibroma, giant cell fibroma and benign fibrous histiocytoma do not react with anti-CD34 antibodies [8].

Cowden syndrome is associated with a higher risk of benign and malignant tumors of the thyroid, breast, kidney, and endometrium [1]. As such, the involvement of multiple sites of SF in a patient should motivate further investigation due to the high probability of diagnosis of Cowden syndrome [1] (chromosomal analysis for mutation in the putative PTEN gene, on chromosome 10q23 [2]). Once the diagnosis is confirmed, as in this case, further clinical and family investigation is recommended [1]. Such studies have not yet been performed in this patient due to lack of adherence to treatment.

These tumors can be treated with surgical resection; occasionally they may relapse – a recurrence time of 2.5 years to 7 years after removal has been reported [10].

conclusions

Circumscribed sclerotic fibroma is a rare benign tumor that is sometimes found in the oral mucosa. This case report shows a very rarely identified oral SF that was found in a patient with a previous diagnosis of Cowden syndrome. The diagnosis of SF was made by histopathology, after excision of the lesions (with free margins). Although it may appear as a solitary, isolated skin lesion, syndromic associations, such as Cowden’s syndrome, should be excluded, especially when multiple sites of SF are involved.

The oral cavity may be the first noticeable manifestation of systemic disease and should not be neglected when conducting a physical examination of the patient.

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