Superficial fibromas are a group of mesenchymal spindle cell lesions with pathomorphological heterogeneity and diverse molecular backgrounds. In part, they may be indicators of an underlying syndrome. Among the best-known entities of superficial fibromas is Gardner fibroma, a plaque-like benign tumor, which is associated with APC germline mutations and occurs in patients with familial adenomatosis polyposis (Gardner syndrome). Affected patients also have an increased risk to develop desmoid fibromatosis (DTF), a locally aggressive neoplasm of the deep soft tissue highly prone to local recurrences. Although a minority of DTFs occur in the syndromic context and harbor APC germline mutations, most frequently their underlying molecular aberration is a sporadic mutation in Exon 3 of the CTNNB1 gene. Up to date, a non-syndromic equivalent to Gardner fibroma carrying a CTNNB1 mutation has not been defined. Here, we present two cases of (sub-)cutaneous tumors with a hypocellular and collagen-rich Gardner fibroma-like appearance and pathogenic, somatic CTNNB1 mutations. We aim to differentiate these tumors from other fibromas according to their histological appearance, immunohistochemical staining profile and underlying somatic CTNNB1 mutations. Furthermore, we distinguish them from locally aggressive desmoid fibromatosis regarding their biological behavior, prognosis and indicated therapeutic strategies. Consequently, we call them CTNNB1-mutated superficial fibromas as a sporadic counterpart lesion to syndromic Gardner fibromas.

Storiform collagenoma, also known as sclerotic fibroma, is a relatively rare benign cutaneous tumor consisting of a proliferation of fibroblasts that shows increased production of type I collagen. It may appear as a solitary, sporadic lesion, or, especially when multiple, associated with Cowden syndrome. Giant cell collagenoma has a histopathologic appearance similar to that of storiform collagenoma with the addition of floret-type giant cells. Herein, we report the finding of multiple giant cell collagenomas arising in an individual with Cowden syndrome. In a review of the published literature, this histopathologic variant appears to be rarely observed in association with Cowden syndrome.

OBJECTIVE: Cowden syndrome (CS) is a multisystem disease with an elevated lifetime risk of internal malignancy. We aim to assess the role of PTEN immunostain as a screening test for CS in a variety of common CS-associated neoplasms, with a particular focus on cutaneous tumors.
METHODS: We retrospectively searched for patients meeting criteria for CS and/or demonstrating germline PTEN mutation from 2008 to 2022. We then performed PTEN immunostains on tumors of these patients as well as control cases.
RESULTS: Our study included 30 patients with CS who had a total of 25 CS-associated malignancies (13 thyroid, 8 breast, and 4 endometrial carcinomas). Specifically, there were 11 patients with biopsy-confirmed CS-associated cutaneous neoplasms, including 1 patient with multiple trichilemmomas and 3 with multiple sclerotic fibromas. In total, 45 CS-associated tumors (6 trichilemmomas, 7 sclerotic fibromas, 5 thyroid carcinomas, 18 adenomatous thyroid nodules, 6 breast carcinomas, and 3 endometrial carcinomas) and 31 non-CS cases (9 trichilemmomas, 5 sclerotic fibromas, 8 adenomatous thyroid nodules, and 3 thyroid, 3 breast, and 3 endometrial carcinomas) were available for PTEN immunohistochemical staining. PTEN expression was lost in 43 (96%) of 45 CS-associated lesions and retained in 30 (97%) of 31 sporadic tumors. The overall sensitivity and specificity of PTEN loss of expression as a screening test for CS were 96% and 97%, respectively.
CONCLUSIONS: PTEN immunohistochemistry on CS-associated tumors, especially trichilemmomas, can serve as a readily accessible and cost-effective screening test for CS.

Sclerotic fibroma (SF) is a rare subset of dermal fibromas that occurs sporadically or in association with Cowden syndrome (CS). We report a case of a patient with known CS and a solitary lesion on the scalp. Histologic examination demonstrated a well-circumscribed lesion with sclerotic dermis and a whorled collagen pattern, multinucleated giant cells, and dendritic spindle cells. Nuclear atypia or mitotic figures were not noted. The giant cells were negative for Melan-A, SOX-10, EMA, SOX-10, and factor XIIIa. These findings are consistent with a giant cell collagenoma (GCC). Despite possible overlap with SF, GCC has not been associated with CS. This makes our case unique and suggests that GCC should be included in the spectrum of CS-associated cutaneous lesions. The diagnosis of SF may lead to the identification of previously undiagnosed CS; accordingly, GCC, even when present as a solitary lesion, may indicate the need for further work-up and screening for CS.

Sclerotic fibroma (SF) is an uncommon yet benign tumor that may occasionally be associated with Cowden\'s disease that presents as an asymptomatic, well-circumscribed lesion. We present a rare case of a patient with a solitary SF of the palpebral conjunctiva. The patient was an 85-year-old male who presented with a right lower lid nodule that was initially treated as a chalazion. Excision yielded a dense mass that was sent to pathology for evaluation. Histologically, the lesion showed a bland storiform spindle cell proliferation embedded in a sclerotic stroma with prominent clefting.

Sclerotic fibroma (storiform collagenoma) is a fibrotic tumor that occurs mainly in patients with Cowden syndrome, but it can also occur in isolation, as detailed in previous reports. Here we present a case of a solitary sclerotic fibroma in cerebellopontine angle. Brain magnetic resonance imaging revealed a lesion showing hypointense signal on both T1 and T2. The lesion was not enhanced after administering gadolinium. The tumor was removed integrally by surgery.

Eosinophilic angiocentric fibrosis (EAF) is a rare tumefactive fibroinflammatory disease with predilection for the upper respiratory tract, characterized by concentric (onionskin) fibrosis around small arterioles with variable intervening storiform fibrosis admixed with chronic inflammatory infiltrates rich in eosinophils. Erythema elevatum diutinum (EED), another autoimmunological disorder that mainly affects acral sites and extensor surfaces, is characterized by neutrophilic leukocytoclastic vasculitis. Rarely, older EED lesions may present as tumefactive nodular (pseudotumoral) fibrous masses closely mimicking EAF. We herein describe four patients (all males) aged 66-70 years who presented with large (median, 7 cm) tumor-like fibrous lesions in the paravertebral region not associated with a known clinical autoimmune disease. All cases were resected surgically with the suspicion of a neoplasm. They displayed a strikingly similar histological appearance with combined features of EAF and nodular fibrous EED. None had evidence of obliterative phlebitis or increased IgG4: IgG ratio. The etiology of this distinctive lesion and its predilection for the paravertebral area of males remains obscure. A distinctive tumefactive localized reaction to trauma caused by degenerative disease of adjacent vertebrae might be a possible explanation.

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

Collagenoma is a rare benign skin lesion classified as a hamartomatous proliferation of normal collagen fibres and varying amounts of elastic fibres. They most frequently occur on the arms or trunk and may present as solitary or multiple lesions, as part of a syndrome (such as Cowden Syndrome, Tuberous Sclerosis, or MEN1) or sporadic and of varying sizes. Herein, we report on a case of large acquired collagenomas found in an unusual location on the dorsum of both feet.

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