Late-onset Proteus syndrome with cerebriform connective tissue nevus and subsequent development of intraductal papilloma

Abstract

Proteus syndrome (PS) is a rare segmental overgrowth disorder caused by a mosaic activating variant in AKT1. The features of PS are often not present at birth but develop during the first few years of life. We describe a 55-year-old female, whose first symptom of overgrowth, a cerebriform connective tissue nevus, occurred at 19 years of age. We report the identification of the AKT1 c.49G > A p.(Glu17Lys) variant in this progressive lesion, the bony overgrowth, and recurrence after surgical intervention. In the sixth decade of life, this individual developed intraductal papillomas within her right breast which were confirmed to contain the same activating AKT1 variant as the connective tissue nevus. While similar neoplasms have been described in an individual with Proteus syndrome, none has been evaluated for the presence of the AKT1 variant. The tumor also contained two likely pathogenic variants in PIK3R1, c.1392_1403dupTAGATTATATGA p.(Asp464_Tyr467dup) and c.1728_1730delGAG p.(Arg577del). The finding of additional genetic variation putatively affecting the PI3K/AKT pathway in the neoplastic tissue may provide preliminary evidence of a molecular mechanism for tumorigenesis in PS. The late onset of symptoms and molecular characterization of the breast tumor expand the clinical spectrum of this rare disorder.

1 |. INTRODUCTION

Proteus syndrome (PS) is a rare disorder characterized by early childhood onset of progressive, segmental overgrowth of skin, bone, and adipose tissues. It is most commonly caused by a mosaic activating variant in AKT1, c.49G > A p.(Glu17Lys), although one individual had a distinct AKT1 variant, c.49_50delinsAG p.(Glu17Arg) (Buser et al., 2020). A dyadic genotype–phenotype approach to the diagnosis of PS combines identification of a pathogenic AKT1 variant with point-assigned phenotypic manifestations to distinguish PS from non-PS overgrowth disorders and AKT1-related overgrowth (Sapp et al., 2019). The physical manifestations of PS are often not present at birth and typically become apparent at 6–18 months of age (Biesecker, 2006).

Among the most common of PS manifestations is the cerebriform connective tissue nevus (CCTN). This lesion typically occurs on the soles of the feet and/or hands with an average age of onset of 2 years (Beachkofsky et al., 2010; Nguyen et al., 2004). The abnormal skin first appears as multiple small nodules and papules that coalesce to form a cerebriform lesion. The area increases to involve a progressively greater proportion of the sole of the foot during childhood until growth plateaus in adulthood (Nathan et al., 2018). However, the small sample size of adults with PS in natural history studies remains a limitation to understanding the long-term outcome of CCTN. Due to the morbidity associated with CCTN, including pain, abnormal gait, and severe malodor, surgical resection may be considered. Despite such interventions, nodular and cerebriform lesions may recur, most commonly at the perimeter of the resected area (Çiloğlu et al., 2015; Ma & Tian, 2014; Uitto et al., 1982; Wu et al., 2016).

Proteus syndrome is associated with an increased risk of tumor development, particularly low-grade ovarian and paratesticular epithelial tumors and meningioma (Gordon et al., 1995; Keppler-Noreuil et al., 2016; Raju et al., 2002). Neoplasms of the breast are less common in PS but may range from hyperplastic fibrocystic changes to intraductal papilloma with foci of ductal carcinoma in situ (DCIS) (Cohen, 1988; Iqbal et al., 2006). A mouse model of PS showed mam-mary duct hyperplasia consistent with this finding in humans (Lindhurst et al., 2019). However, the relationship of PS to breast tumors is not well understood.

We present a woman with late-onset PS characterized by progressive plantar CCTN and nonmalignant neoplastic breast lesions. We discuss the implications of this unique presentation to our understanding of the natural history of this rare disease.

2 |. CLINICAL REPORT

A 55-year-old White female presented to the National Institutes of Health Clinical Center (NIHCC) for evaluation of PS-related overgrowth. She provided written informed consent to the Natural History of Proteus Syndrome and Related Disorders study (NCT00001403) approved by the National Institutes of Health Institutional Review Board.

She was born to nonconsanguineous parents following an uncomplicated pregnancy. No overgrowth was noted at birth. The first signs of overgrowth presented at 19 years of age as small, nonpainful, non-pruritic flesh-colored papules on the medial sole of the left foot. These grew slowly over several years. Initially, the lesions primarily grew outward from the skin of the medial arch of the left foot, then later involved skin along the medial aspect extending toward the great toe, increasing in nodularity before evolving into a cerebriform appearance at 33 years of age.

The CCTN was resected three times. The first resection occurred when she was 35 years old. Over the following 5 years, there was regrowth of the lesion to a size of 6 cm in greatest diameter. At age 41 years, she underwent a second resection with split-thickness skin autograft from her left hip. Following the second CCTN resection, she experienced gradual CCTN regrowth at the perimeter of the graft site. At this time, she developed a left hallux valgus deformity. A small, flesh colored papule also developed on the contralateral great toe. At 48 years of age, the left foot lesion had become painful and was 7 cm in diameter and exophytic, extending 3 cm from the foot. A mosaic AKT1 c.49G > A p.(Glu17Lys) variant was identified by Sanger sequencing of a skin punch biopsy of the CCTN. This variant was not identified in a peripheral blood sample.

She underwent a third resection with a split-thickness skin graft using donor skin from the upper left thigh and excision of the left great toe papule. Histopathology showed expansion of the dermis with thickened collagen bundles consistent with a connective tissue nevus. In the years following surgery, she showed signs of CCTN regrowth along the border of the skin graft (Figure 1a–c). Images prior to the first and second CCTN resections were not available.

FIGURE 1.

Skin and bone overgrowth in bilateral feet. Photography of the left foot showing progression of CCTN from (a) 48 years of age immediately prior to third resection, (b) to 50 years of age and (c) 55 years of age. At 55 years of age radiography of (d) the right foot showed overgrowth of the tarsal and navicular bones and (e) right foot hallux valgus deformity with metatarsal overgrowth

On physical examination at the NIHCC, the CCTN was present on her left sole at the margin of the previous skin graft (Figure 1c). On the left great toe, there were two nodules, one of which displaced the toenail medially. There were two small nodules on the right great toe proximal and lateral to the toenail. Hyperkeratosis of the left sole and in the grooves between the CCTN and skin graft was present. She reported pain caused by friction with footwear but had no plans for further excision. We performed a skeletal survey, which did not show skeletal or bony overgrowth, except for enlargement of the osseous structures of the right midfoot at the talonavicular and tarsal-metatarsal articulations and left-sided hallux valgus (Figure 1d,e).

Routine mammogram screening at 49 years of age showed no lesions in the left breast and a single mass lesion in the right breast, which was a new finding when compared to mammography 7 years prior. The lesion was considered to be benign. Repeat mammography at 51 years of age showed six nodular foci in the right breast. She denied any pain or nipple discharge. These were again considered to be benign and monitored by serial mammography. Follow-up imaging at 55 years of age showed new nodules and enlargement of pre-existing ones only in the right breast. Ultrasound showed numerous nodules in the right breast, the largest of which was a lobular, hypoechoic lesion, 4 cm from the nipple measuring 9.8 × 9.1 × 8.3 mm. She was referred to a breast oncologist who recommended core needle biopsy to rule out a malignant neoplasm. Histopathology showed intraductal papilloma with associated ductal and stromal hyperplasia of the breast (Figure 2). No areas of DCIS were observed in the core biopsy. She continues to be monitored by serial imaging.

FIGURE 2.

Hematoxylin and eosin stained section of breast core biopsy with epithelial and stromal hyperplasia

Genetic testing of the formalin-fixed paraffin-embedded biopsy was performed using the TruSight Oncology 500 Gene Panel v2 (Illumina) and QIAGEN Clinical Insight (QCI) was then used for variant filtering, annotation, classification, and interpretation. The QCI filter includes variants with read depth of at least 50 and allele fraction of at least 5%. It excludes variants with an allele frequency greater than or equal to 1.0% in public databases unless established pathogenic common variant. These variants are classified by American College of Medical Genetics (ACMG) criteria and subsequently reassessed by a molecular pathologist with oncology expertise who assesses for a potential oncogenic role. A pathogenic activating variant in AKT1, c.49G > A p.(Glu17Lys), was detected with a variant allele fraction (VAF) of 7%. Two likely pathogenic variants in PIK3R1 were identified: c.1392_1403dupTAGATTATATGA p.(Asp464_Tyr467dup) with VAF of 5.6% and c.1728_1730delGAG p.(Arg577del) with VAF 16.0%. In addition, there was a VUS in FAT1, c.1504A > G p.(Ile502Val), with VAF 8.96%. Pathogenic variants, presumed to be germline, in MITF, c.1273G > A p.(Glu425Lys), and SHQ1, c.828_831delTGAT p. (Asp277fs*27), were detected with VAFs of 49.0% and 48.0% respectively (Supplemental Table S1).

To evaluate for subclinical pulmonary findings, a low-dose chest computed tomography was performed and did not show cystic lung disease, a known manifestation of PS (Mirmomen et al., 2021). Additional clinical history includes asthma, seasonal allergies, and varicose veins in the left leg with occasional superficial thrombosis, but no history of deep vein thrombosis. She has given birth to three healthy children and has had three miscarriages. She has a family history of melanoma in a sister, but no family history of overgrowth or other cancers.

3 |. DISCUSSION

This individual meets the diagnostic criteria for clinical molecular diagnosis of PS with a confirmed pathogenic AKT1 variant, mosaic distribution, sporadic occurrence, and progressive course of sufficient phenotypic manifestations (Sapp et al., 2019). The CCTN onset at age 19 years and continued growth into the sixth decade of life may indicate that there is a wider spectrum of CCTN onset and progression in adults with PS than previously understood. The quality of the CCTN in this individual is unique as well. Lesions most frequently arise on the ball of the foot and spread along the plantar surface (Nathan et al., 2018). In contrast, the presented lesion arose on the medial aspect of the foot and progressed outward before extending toward the great toe (Figure 1a–c).

Surgical intervention is considered only for those with severe CCTN. However, regrowth is common. Among four reports of CCTN surgical resection with skin grafting, three experienced recurrence (Çiloğlu et al., 2015; Ma & Tian, 2014; Uitto et al., 1982; Wu et al., 2016). This risk of CCTN recurrence highlights the need for the development of nonsurgical therapeutics to slow and/or prevent CCTN growth in individuals with PS. In neurofibromatosis type 1, the use of selumetinib for inoperable plexiform neurofibromas offers a proof of principle for treating benign growths with signal transduction inhibitors (Gross et al., 2020).

Isolated CCTN with onset in the second decade of life has been previously reported but with limited evaluation for additional features of PS (Çiloğlu et al., 2015; Luo et al., 2007). While one of these individuals is reported to additionally have bone overgrowth raising suspicion of a diagnosis of PS, neither report included a genetic evaluation, making it difficult to determine if these presentations are due to AKT1-mediated overgrowth, PIK3CA-related overgrowth, which has also been reported in CCTN, or another mechanism (Keppler-Noreuil et al., 2019). The finding of bony overgrowth in the foot contralateral to the CCTN supports the utility of a comprehensive evaluation with x-ray and molecular analyses of the PI3K/AKT pathway in individuals who present with apparent isolated CCTN.

Intraductal papilloma and hyperplasia of the breast have been reported in individuals with PS (Cohen, 1988; Iqbal et al., 2006). One report described an individual with PS with both neoplastic (intraductal papilloma with DCIS) and nonneoplastic (cysts, connective tissue, and epithelial proliferation) changes of the breast (Iqbal et al., 2006). The authors proposed that the carcinoma was a manifestation of PS, although the lesions were not molecularly assayed. In the individual reported here, identification of the activating AKT1 c.49G > A p.(Glu17Lys) variant in the intraductal papilloma is consistent with the hypothesis that this is a PS-related lesion. The presence of two PIK3R1 variants, c.1392_1403dupTAGATTATATGA p. (Asp464_Tyr467dup) and c.1728_1730delGAG p.(Arg577del), in addition to the AKT1 variant suggests that multiple hits in the PI3K/AKT pathway may have contributed to or been required for tumor development (Kader et al., 2020). The PIK3R1 variant, c.1392_1403dupTAGATTATATGA p.(Asp464_Tyr467dup), has been identified as a mosaic variant in an individual with a clinical diagnosis of Klippel-Trenaunay syndrome (Cottrell et al., 2021).

Driver mutations activating the PI3K/AKT pathway are commonly found in breast carcinomas and benign papillomas (Guillet et al., 2020). The additional variants in PIK3R1, which encodes an inhibitory protein upstream of AKT1, may further promote AKT1 activation and related signaling pathways such as the MAPK pathway (Cheung et al., 2014). Further molecular investigation of this and other breast lesions in PS is needed to better characterize the mutational profile and clonality of these tumors. However, the findings in this individual suggest that additional hits following existing mosaic AKT1 have contributed to neoplastic growth in the breast.

The somatic mutational landscape of breast cancer is relevant to these results. In COSMIC, of the 800 tumors that harbor the AKT1 c.49G > A p.(Glu17Lys) variant, 361 are breast tumors (accessioned November 19, 2021). When looked at from the vantage point of breast tumors, about 4% of all breast tumors harbor AKT1 variants (PIK3CA variants being the most common at 29%). Of PIK3R1 variants in COSMIC, breast is the 13th most common, of 44 tumor types. We conclude that AKT1 and PIK3R1 somatic variants are likely drivers of breast tumors, both sporadic, and in individuals with PS.

The risk of breast tumor development in the context of the presumed germline MITF variant, c.1273G > A,p.Glu425Lys, is unknown. A systematic review with meta-analysis and review of The Cancer Genome Atlas found an association between this variant and melanoma but not breast carcinoma (Guhan et al., 2020). Neither the pro-band’s sister, who had a history of melanoma, nor other family members had been evaluated for this variant. Other variants in MITF are associated with disorders of hypopigmentation and sensorineural hearing loss such as Waardenburg Syndrome and Tietz Syndrome (Leger et al., 2012). This individual had no significant hypopigmentary changes and denied hearing loss.

Variants in SHQ1 and FAT1 may play a role in oncogenesis. However, the SHQ1 variant identified in this individual, c.828_831delTGAT p.(Asp277fs*27), is present in 0.1% of Europeans in gnomAD (accessioned March 11, 2022). The classification of this variant as pathogenic was based on oncogenic potential because this variant is predicted to affect a functionally necessary protein domain and loss of function variants in SHQ1 have been associated with malignant tissues (Machado-Pinilla et al., 2012).

The development of intraductal papilloma over three decades after the onset of CCTN suggests a risk of tumor development even in individuals with apparent anatomically restricted PS. Importantly, the malignant potential of these lesions is unknown and there is insufficient evidence to recommend that individuals with PS without a history of breast lesions would benefit from additional breast cancer screening or risk reducing surgery. Inhibitors of the PI3K pathway, such as alpelisib, are approved for metastatic breast cancer in combination with hormonal therapy. While this individual was surgically managed, and no systemic therapy is indicated for her current disease extent, target-directed treatment options could be considered should this individual develop malignant and/or metastatic disease.

Progressive course, sporadic occurrence, and mosaic distribution are mandatory diagnostic criteria for PS (Sapp et al., 2019). Although this individual meets these criteria, the late onset of overgrowth and 30-year interval from the onset of her CCTN to her breast lesions is a unique presentation of this rare disease. This example of late-onset PS expands our knowledge of the spectrum of the disorder, particularly of symptoms during adulthood. The presence of an activating AKT1 variant in the benign breast lesion along with previous reports of similar lesions in individuals with PS further support this manifestation as part of the PS phenotype. This case raises the importance of comprehensively evaluating those with apparent isolated CCTN for additional manifestations of PS.

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available from the corresponding author upon reasonable request.