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Logo of bmjcrInstructions for authorsCurrent ToCBMJ Case Reports
BMJ Case Rep. 2010; 2010: bcr09.2009.2251.
Published online Feb 8, 2010. doi:  10.1136/bcr.09.2009.2251
PMCID: PMC3028296
Rare disease
Immunohistochemical analysis of a merkeloma observed in a patient affected by hereditary haemorrhagic telangiectasia
Elisa Rossi,1 Laura Boeri,2 Patrizia Morbini,3 Fabio Pagella,4 Andrea Colombo,4 Elina Matti,4 Carla Olivieri,2 Vincenzo Villanacci,1 Antonella Minelli,2 Elisabetta Buscarini,5 Cecilia Canzonieri,2 and Cesare Danesino6
1Spedali Civili di Brescia, Second Department of Pathology, Piazzale Spedali Civili, 1, Brescia, 25123, Italy
2University of Pavia, Medical Genetics, Via Forlanini, 14, Pavia, 27100, Italy
3University of Pavia, IRCCS Policlinico S. Matteo, Pavia, Pathological Anatomy Department, Via Forlanini, 14, Pavia, 27100, Italy
4IRCCS Policlinico S. Matteo, Pavia, ENT Unit, Via Golgi, 19, Pavia, 27100, Italy
5Ospedale Maggiore of Crema, Gastroenterology Unit, Via Macall, Crema, 26013, Italy
6University of Pavia, Via Forlanini, 14, 27100 Pavia, Pavia, 27100, Italy
Correspondence to Cesare Danesino, cidilab/at/
Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterised by epistaxis, telangiectases, and multiorgan vascular dysplasia. Mutations of the ENG and ACVRL1 genes cause at least 80% of cases. We report the first case of merkeloma found in a patient with HHT carrying an ENG mutation. We analysed the tumour with immunohistochemical methods using primary antibodies against CD105 (endoglin), TGF-β, Smad4, CD31 and CD34. Tumour cells were positive for Smad4, weakly positive for TGF-β, and negative for CD105. Vasal endothelial cells were highly positive for CD105, CD31 and CD34. No remarkable differences between cancer and normal cells in our patient or between the patient’s merkeloma and two control merkelomas were observed. The presence of a merkeloma in an HHT patient could be an occasional association, but to certainly assume it further investigations are needed.
Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterised by epistaxis, telangiectases, and multiorgan vascular dysplasia.1 Mutations of the ENG and ACVRL1 genes cause at least 80% of cases. Merkeloma is a rare neoplasm of Merkel cells—epidermis sensory touch receptors.2 We report the first case of merkeloma found in an HHT patient carrying an ENG mutation. The case presented is relevant because of the association in the same patient of two very rare disorders. A minimum prevalence rate of HHT is estimated to be overall 1 in 10,0003 and because of genetic heterogeneity with mutation in at least two disease causing genes (ENG-HHT1 and ACVRL1-HHT2),4,5 rarer if we consider HHT1 alone. A comprehensive review about clinical and genetic data on HHT is available at
Merkeloma is a primary neuroendocrine carcinoma of the skin. Merkeloma cell carcinoma (MCC) classically manifests itself with a rapid growth, painless, non-ulcerated lesion, red to violaceous nodule or plaque on the sun-exposed skin of elderly patients. The reported age range of patients is from 7–97 years, although the majority of patients are >65 years. MCC is a very rare neoplasm, with fewer than 1000 reported cases to date.2 The most frequently reported sites are on the head and neck, extremities and trunk. Most tumours are approximately 2–4 cm in diameter, although those of the head and neck tend to be smaller. No association has ever been reported between the two disorders. When two very rare events occur simultaneously in the same patient, two possible interpretations are possible: chance association or causal relationship. The easiest way to identify a causal relationship is to record several cases in which the two diseases are associated. We decided to report our patient to promote the collection of other similar cases.
We report the case of a 72-year-old Italian male patient who was diagnosed with HHT according to the Curaçao criteria: (1) epistaxis present since the age of 16 which has worsened through his life; (2) a large number of telangiectases on typical areas such as lips, tongue, gums, palate, fingers and ears; (3) a pulmonary arteriovenous malformation (PAVM) which was identified in 2006; (4) a (likely) positive family history because of pulmonary vascular dysplasia in his father. A mutation in the ENG gene was found, and identified also in his 33-year-old daughter who, to date, has shown epistaxis as the only HHT related clinical symptom. The patient did not refer to any other illness up to the age of 72 years.
In 2007 the patient sought medical assistance because of the presence of a brown-red neoformation on the tip of his nose, which bled easily on touch, about 1 cm in diameter and surrounded by multiple telangiectases (fig 1). The lesion was surgically removed and histological examination revealed a Merkel cell carcinoma.
Figure 1
Figure 1
Intraoperative view: presence of a brown-red neoformation of the tip of the nose surrounded by multiple telangiectases.
The diagnosis of HHT prompted a mutation analysis, which demonstrated a c. 1478 del G (p. C493SfsX25) in the exon 11 of the ENG gene (see Olivieri et al6 for methods) (fig 2). The mutation identified a deletion of a single base, which introduces a stop codon. This kind of mutation, originating a truncated protein, is commonly assumed to be causative of the disease.
Figure 2
Figure 2
The sequence of polymerase chain reaction (PCR) product shows a deletion of 1 bp (c.1478delG (p. C493SfsX25)) located in exon 11 of ENG gene.
Then we studied the immunohistochemical expression of endoglin, TGF-β and Smad4 on the merkeloma cells (fig 3); the three proteins belong to the same pathway, relevant for blood vessel formation and maturation. Vessels were identified by studying CD31 and CD34. No evident vascular alterations were observed in the merkeloma (images not included).
Figure 3
Figure 3
Immunohistochemical staining of sections of merkeloma in the index case: (a) haematoxylin and eosin; (b) endoglin; (c) TGF-β; (d) Smad4.
To evaluate Smad4, TGF-β, CD105, CD31 and CD34 we performed an immunohistochemical analysis. The immunohistochemical method involved sequential application of primary antibody (Santa Cruz Biotechnology Inc, Santa Cruz, USA) to Smad4 (diluted 1:50), TGF-β (diluted 1:200), CD105 (diluted 1:50), CD31 (Novocastra Laboratories, Newcastle, UK, diluted 1:50) and CD34 (Neomarkers, Bioptica, Milan, Italy, diluted 1:30). We used the NovoLink Polymer Detection System (Novocastra Laboratories, Newcastle, UK).
Immunostaining was considered positive for all the antibodies analysed when at least 10% of neoplastic cells (for Smad4, TGF-β, CD105) and of endothelial cells (for CD31, CD34) were stained.
Tumour cells were positive for Smad4, weakly positive for TGF-β, and negative for CD105. Vasal endothelial cells were highly positive for CD105, CD31 and CD34. We did not observe remarkable immunohistochemical differences either between cancer and normal cells for CD105 and Smad4 of the same patient, or between the patient’s merkeloma and two merkeloma controls.
Outcome and follow-up
As far as the patient’s nose bleeding is concerned, after treatment with argon plasma laser it is now well controlled. No recurrence of merkeloma was observed locally nor has any evidence of metastatic spreading been reported. PAVM is waiting for embolisation.
The occurrence of a nonsense mutation in the endoglin gene is expected to cause a 50% reduction in endoglin levels, as haploinsufficiency is probably the established mechanism by which HHT develops.7 However, no reduction in endoglin levels in the merkeloma observed in our patient was recognisable after staining the slides with CD105 antibodies; as overexpression of endoglin in cancer tissues has been widely reported, this is a possible explanation for our findings.8,9 Immunochemical staining should be sensitive enough to demonstrate a 50% reduction of endoglin, as demonstrated in placental tissues.10
As it is well known that angiogenesis is relevant in cancer development and progression, we decided to test on the merkeloma the expression of two other proteins, TGF-β and Smad4, which belong to the same pathway, and are relevant for blood vessel formation and maturation. Again no difference was observed between our case and control merkelomas, indicating that the mutation in the endoglin gene does not affect the expression of the indicated proteins in this case.
We did not find any vascular malformation in the tumour tissues, and this observation is in keeping with the data by Letarte et al who failed to demonstrate vascular alteration in as highly vascularised tissue as placentas from babies carrying ENG mutations.10
The reason why vascular malformations are frequently observed in some organs such as liver, lung and brain, but not in others, is not yet understood.
No similar cases have been reported, to the best of our knowledge; we found several reports in the literature concerning single cases of the association of HHT with different cancer types.11 Overall these findings suggest that our case and those found in the literature are chance associations. No information is currently available about a possible effect, if any, of a mutated endoglin on a tumour developing in an HHT patient.
Learning points
  • Association between a rare genetically determined disorder such as hereditary haemorrhagic telangiectasia (HHT) and a rare cancer such as merkeloma is possible.
  • Endoglin is overexpressed in cancer tissues, but no information is available about the effect, if any, of its mutations on cancer risk and development.
  • Reporting new cases of association between HHT1 and any type of cancer may help to understand some of the biological effects of endoglin.
Competing interests: None.
Patient consent: Patient/guardian consent was obtained for publication.
1. Abdalla SA, Letarte M. . Hereditary haemorrhagic telangiectasia: current views on genetics and mechanisms of disease. J Med Genet 2006; 43: 97–110. [PMC free article] [PubMed]
2. Smith PD, Patterson JW. Merkel cell carcinoma (neuroendocrine carcinoma of the skin). Am J Clin Pathol 2001; 115Suppl: S68–78. [PubMed]
3. Guttmacher AE, Marchuk DA, White RI., Jr Hereditary hemorrhagic telangiectasia. N Engl J Med 1995; 333: 918–24. [PubMed]
4. McAllister KA, Grogg KM, Johnson DW, et al. Endoglin, a TGF-beta binding protein of endothelial cells, is the gene for hereditary haemorrhagic telangiectasia type 1. Nat Genet 1994; 8: 345–51. [PubMed]
5. Johnson DW, Berg JN, Baldwin MA, et al. Mutations in the activin receptor-like kinase 1 gene in hereditary haemorrhagic telangiectasia type 2. Nat Genet 1996; 13: 189–95. [PubMed]
6. Olivieri C, Pagella F, Semino L, et al. Analysis of ENG and ACVRL1 genes in 137 HHT Italian families identifies 76 different mutations (24 novel). Comparison with other European studies. J Hum Genet 2007; 52: 820–9. [PubMed]
7. Cymerman U, Vera S, Pece-Barbara N, et al. Identification of hereditary hemorrhagic telangiectasia type 1 in newborns by protein expression and mutation analysis of endoglin. Pediatr Res 2000; 47: 24–35. [PubMed]
8. Fonsatti E, Altomonte M, Nicotra MR, et al. Endoglin (CD105): a powerful therapeutic target on tumor-associated angiogenetic blood vessels. Oncogene 2003; 22: 6557–63. [PubMed]
9. Bernabeu C, Conley BA, Vary CP. Novel biochemical pathways of endoglin in vascular cell physiology. J Cell Biochem 2007; 102: 1375–88. [PMC free article] [PubMed]
10. Chan NL, Bourdeau A, Vera S, et al. Umbilical vein and placental vessels from newborns with hereditary haemorrhagic telangiectasia type 1 genotype are normal despite reduced expression of endoglin. Placenta 2004; 25: 208–17. [PubMed]
11. Kluger N, Riviére S, Coupier I, et al. Association of hereditary haemorrhagic telangiectasia (Rendu-Osler-Weber syndrome) and malignant melanoma in two patients. Melanoma Res 2007; 17: 201–3. [PubMed]
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