Multiple endocrine neoplasia type 2A with cutaneous lichen amyloidosis

Hereditary Medullary Thyroid Cancer: Genotype-Phenotype Correlation

Multiple endocrine neoplasia type 2 (MEN2) is an autosomal dominant hereditary cancer syndrome caused by germline variants in the REarranged during Transfection (RET) proto-oncogene. MEN2 is caused by autosomal dominant gain-of-function mutations in the RET proto-oncogene. There are two clinically distinct types of MEN2 syndrome, termed MEN2A and MEN2B. MEN2A is associated with medullary thyroid carcinoma (MTC) and the less frequent occurrence of pheochromocytoma, primary hyperparathyroidism, or both, rarely with cutaneous lichen amyloidosis or Hirschsprung's disease. MEN2B is associated with MTC, pheochromocytoma, and other noncancerous abnormalities, such as Marfanoid habitus and ganglioneuromas of the intestines. Specific RET mutations suggest a predilection toward a particular phenotype and clinical course with strong genotype-phenotype correlation. Based upon these genotype-phenotype correlations, RET mutations are stratified into three risk levels, i.e., highest, high, and moderate risk, based on the age of onset and the penetrance of the MTC. Children in the highest risk category develop MTC within the first year of life and should undergo thyroidectomy in their first year, perhaps even in their first months of life. In children in the high-risk category, ultrasound of the neck and calcitonin (Ctn) measurement should be performed prior to thyroidectomy. Thyroidectomy should typically be performed at 5 years of age or earlier, depending on the presence of elevated serum Ctn levels. However, heterogeneity in disease expression and progression within these groups varies considerably. To personalize disease management, the decision regarding the age of prophylactic thyroidectomy is no longer based upon genotype alone but is currently driven by additional clinical data, the most important being serum Ctn levels. In the moderate-risk group, the timing of thyroidectomy is particularly dependent on the Ctn level. Personalized management also includes decisions about the best age to begin biochemical screening for pheochromocytoma and primary hyperparathyroidism.

Histopathology of C Cells and Medullary Thyroid Carcinoma

C cells are the neuroendocrine cell component of the thyroid gland that embryologically arise from the pharyngeal endoderm. Normal C cells are concentrated in the upper two-thirds of both lateral lobes, appear singly or in small groups dispersed in, among or peripherally to the follicles, and are involved in the production of calcitonin. Reactive C-cell hyperplasia should be differentiated from proliferation of atypical C cells (neoplastic C-cell hyperplasia) which is considered an intraepithelial neoplasia of C cells/medullary carcinoma in situ, a precursor lesion associated to familial medullary thyroid carcinoma (MTC). MTC typically exhibits a lobular and/or trabecular growth pattern with amyloid deposits; however, due to its great histological variability, immunohistochemical positivity for calcitonin, carcinoembryonic antigen, calcitonin-gene-related peptide, insulinoma-associated protein 1, and/or other markers is necessary to confirm diagnosis. Investigation of germline RET proto-oncogene mutation is mandatory to identify familial MTC. Somatic RET mutations or fusions as well as RAS mutations in cytological and/or biopsy samples may represent therapeutic targets. Mixed medullary and follicular-derived cell carcinoma is a heterogeneous group of tumors which needs to be distinguished from collision tumors.

Integrated Network-Based Analysis of Diseases Associated with Amyloid Deposition Through a Disease-Protein-Drug Network

Background: At present, the complexity that governs the associations between different biological entities is understood better than ever before, owing to high-throughput techniques and systems biology. Networks of interactions are necessary not only for the visualization of these complex relationships but also because their analysis tends to be valuable for the extraction of novel biological knowledge. Methods: For this reason, we constructed a disease-protein-drug network, focusing on a category of rare protein-misfolding diseases, known as amyloidoses, and on other pathological conditions also associated with amyloid deposition. Apart from the amyloidogenic proteins that self-assemble into fibrils, we also included other co-deposited proteins found in amyloid deposits. Results: In this work, protein-protein, protein-drug, and disease-drug associations were collected to create a heterogenous network. Through disease-based and drug-based analyses, we highlighted commonalities between diseases and proposed an approved drug with prospects of repurposing. Conclusions: The identified disease associations and drug candidates are proposed for further study that will potentially help treat diseases associated with amyloid deposition.

Endocrine Perspective of Cutaneous Lichen Amyloidosis: RET-C634 Pathogenic Variant in Multiple Endocrine Neoplasia Type 2

BACKGROUND

Medullary thyroid carcinoma (MTC), the third most frequent histological type of thyroid malignancy, may be found isolated or as part of multiple endocrine neoplasia type 2 (MEN2). One particular subtype of this autosomal dominant-transmitted syndrome includes an association with cutaneous lichen amyloidosis, although, generally, a tide genotype-phenotype correlation is described in patients who carry RET proto-oncogene pathogenic variants.

METHODS

Our objective was to provide an endocrine perspective of a case series diagnosed with RET-positive familial MTC associated with cutaneous primary lichen amyloidosis amid the confirmation of MEN2. Six members of the same family had cutaneous lesion with different features (from hyperpigmented, velvety to red/pink appearance) and four of them harbored a RET pathogenic variant at 634 codon (exon 11): c.1900T>G, p.634G (TGC634CGC).

RESULTS

All six patients were females with the lesion at the interscapular region. Except for two women, four of these subjects were investigated and had MTC (three of them with postoperatory confirmation). The youngest affected individual was 6 years old. The three adult females were confirmed with RET pathogenic variant during their 30s, while the girl underwent the familial screening as a newborn. None of them had primary hyperparathyroidism until the present time, except for one subject, and two out of the three adults also had bilateral pheochromocytoma. Notably, all patients were rather asymptomatic from the endocrine perspective at the moment when endocrine tumor/cancer was confirmed, and the skin was progressively affected a few years before the actual MEN2 confirmation.

CONCLUSIONS

This case series highlights the following key message: awareness of the dermatologic findings in MTC/MEN2 patients is essential since lesions such as cutaneous lichen amyloidosis might represent the skin signature of the endocrine condition even before the actual endocrine manifestations. These data add to the limited published reports with respect to this particular presentation, noting the fact that RET-C634 is the most frequent pathogenic variant in MEN2-associated lichen amyloidosis; females are more often affected; the interscapular region is the preferred site; the age of diagnosis might be within the third decade of life, while we reported one of the youngest patients with the lesion. The same RET pathogenic variant is not associated with the same dermatologic features as shown in the vignette. The same RET mutation does not mean that all family members will present the same skin anomaly.

Thyroid Malignancy and Cutaneous Lichen Amyloidosis: Key Points Amid RET Pathogenic Variants in Medullary Thyroid Cancer/Multiple Endocrine Neoplasia Type 2 (MEN2)

We aimed to provide an updated narrative review with respect to the RET pathogenic variants and their implications at the clinical and molecular level in the diagnosis of medullary thyroid cancer (MTC)/multiple endocrine neoplasia (MEN) type 2, particularly with respect to the presence of cutaneous lichen amyloidosis (CLA). We searched English-language, in extenso original articles with no timeline nor study design restriction that were published on PubMed. A traditional interplay stands for CLA and MTC in MEN2 (not MEN3) confirmation. While the connection has been reported for more than three decades, there is still a large gap in understanding and addressing it. The majority of patients with MEN2A-CLA have RET pathogenic variants at codon 634; hence, it suggests an involvement of this specific cysteine residue in both disorders (most data agree that one-third of C634-positive subjects have CLA, but the ranges are between 9% and 50%). Females seem more prone to MEN2-CLA than males. Non-C634 germline RET pathogenic variants included (at a low level of statistical evidence) the following: RET V804M mutation in exon 14 for MTC-CLA (CLA at upper back); RET S891A mutation in exon 15 binding OSMR variant G513D (familial MTC and CLA comprising the lower legs to thighs, upper back, shoulders, arms, and forearms); and C611Y (CLA at interscapular region), respectively. Typically, CLA is detected at an early age (from childhood until young adulthood) before the actual MTC identification unless RET screening protocols are already applied. The time frame between CLA diagnosis and the identification of RET pathogenic variants was between 5 and 60 years according to one study. The same RET mutation in one family is not necessarily associated with the same CLA presentation. In MTC/MEN2 subjects, the most affected CLA area was the scapular region of the upper back. Alternatively, another hypothesis highlighted the fact that CLA is secondary to long-term prurit/notalgia paresthetica (NP) in MTC/MEN2. OSMR p. G513D may play a role in modifying the evolutionary processes of CLA in subjects co-harboring RET mutations (further studies are necessary to sustain this aspect). Awareness in CLA-positive patients is essential, including the decision of RET testing in selected cases.

Coexistent Lichen Amyloidosis and Acquired Reactive Perforating Collagenosis in Type 2 Diabetes Mellitus and Post-Thyroidectomy Hypothyroidism Due to Papillary Thyroid Carcinoma: A Rare Case

An abundance of endocrine receptors is expressed on the skin and becomes the target of many hormones. This was associated with various skin diseases that might occur in some endocrine diseases eg, lichen amyloidosis (LA) and acquired reactive perforating collagenosis (ARPC). Here, we report a coexistent LA and ARPC in a 55-year-old woman, characterized with multiple pruritic hyperkeratotic papules and plaques on both arms accompanied by pruritic hyperkeratotic papules and nodules on both legs. She had a history of type 2 diabetes mellitus (DM) and post-thyroidectomy hypothyroidism due to papillary thyroid carcinoma. Histopathological examination revealed amyloid deposition in the papillary dermis corresponding with LA and cup-shaped epidermal depression filled with collagen corresponding with ARPC. The hyperkeratotic papules and nodules flattened in one month after application of 0.05% clobetasol propionate ointment with occlusion on both arms and 0.05% retinoic acid gel on both legs. Hyperkeratotic papules, nodules, and plaques in a patient with a history of endocrine diseases, such as type 2 DM and thyroid disorders should undergo histopathological examination to confirm the diagnosis of skin diseases eg, LA or ARPC.

Approach of Multiple Endocrine Neoplasia Type 1 (MEN1) Syndrome-Related Skin Tumors

Non-endocrine findings in patients with MEN1 (multiple endocrine neoplasia) syndrome also include skin lesions, especially tumor-type lesions. This is a narrative review of the English-language medical literature including original studies concerning MEN1 and dermatological issues (apart from dermatologic features of each endocrine tumor/neuroendocrine neoplasia), identified through a PubMed-based search (based on clinical relevance, with no timeline restriction or concern regarding the level of statistical significance). We identified 27 original studies involving clinical presentation of patients with MEN1 and cutaneous tumors; eight other original studies that also included the genetic background; and four additional original studies were included. The largest cohorts were from studies in Italy (N = 145 individuals), Spain (N = 90), the United States (N = 48 and N = 32), and Japan (N = 28). The age of patients varied from 18 to 76 years, with the majority of individuals in their forties. The most common cutaneous tumors are angiofibromas (AF), collagenomas (CG), and lipomas (L). Other lesions are atypical nevi, basocellular carcinoma, squamous cell carcinoma, acrochordons, papillomatosis confluens et reticularis, gingival papules, and cutaneous T-cell lymphoma of the eyelid. Non-tumor aspects are confetti-like hypopigmentation, café-au-lait macules, and gingival papules. MEN1 gene, respective menin involvement has also been found in melanomas, but the association with MEN1 remains debatable. Typically, cutaneous tumors (AF, CG, and L) are benign and are surgically treated only for cosmetic reasons. Some of them are reported as first presentation. Even though skin lesions are not pathognomonic, recognizing them plays an important role in early identification of MEN1 patients. Whether a subgroup of MEN1 subjects is prone to developing these types of cutaneous lesions and how they influence MEN1 evolution is still an open issue.